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Planets
Solar system paper
Contents
1
Jupiter
1.1
1.2
1
Structure
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
1.1.1
Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
1.1.2
Mass and size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
1.1.3
Internal structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
1.2.1
Cloud layers
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
1.2.2
Great Red Spot and other vortices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4
1.3
Planetary rings
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4
1.4
Magnetosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
1.5
Orbit and rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
1.6
Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
1.7
Research and exploration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
1.7.1
Pre-telescopic research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
1.7.2
Ground-based telescope research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
1.7.3
Radiotelescope research
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
1.7.4
Exploration with space probes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
Moons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
1.8
1.9
1.8.1
Galilean moons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
1.8.2
Classification of moons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
Interaction with the Solar System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
1.9.1
11
Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.10 Possibility of life
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
1.12 See also . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
1.13 Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
1.14 References
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
1.15 Further reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18
1.16 External links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18
Mars
19
1.11 Mythology
2
2.1
Physical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19
2.1.1
20
Internal structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
i
ii
CONTENTS
2.1.2
Surface geology
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20
2.1.3
Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21
2.1.4
Hydrology
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21
2.1.5
Geography and naming of surface features . . . . . . . . . . . . . . . . . . . . . . . . . .
23
2.1.6
Atmosphere
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26
2.1.7
Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28
2.2
Orbit and rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28
2.3
Search for life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29
2.4
Habitability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
2.5
Exploration missions
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
2.6
Astronomy on Mars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
2.7
Viewing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31
2.7.1
32
2.8
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
32
2.8.1
Ancient and medieval observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33
2.8.2
Martian “canals” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33
2.8.3
Spacecraft visitation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
34
In culture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
34
Intelligent “Martians” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
34
2.10 Moons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
36
2.11 Gallery
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
37
2.12 See also . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
37
2.13 Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
37
2.14 References
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
37
2.15 External links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
45
Mercury
47
3.1
Common meanings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
47
3.2
Places . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
47
3.3
In the military . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
47
3.4
Transportation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
47
3.5
In entertainment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
47
3.5.1
Music . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
47
3.5.2
Comics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
3.5.3
Other . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
3.6.1
Computing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
3.7
Sports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
3.8
Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
3.9
Radio stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
3.10 In business . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
3.11 Other uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
2.9
Historical observations
2.9.1
3
Closest approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6
CONTENTS
4
3.12 See also . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
49
Neptune
50
4.1
History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
50
4.1.1
Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
50
4.1.2
Naming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
51
4.1.3
Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
52
Composition and structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
52
4.2.1
Internal structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
52
4.2.2
Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
52
4.2.3
Magnetosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
53
4.3
Planetary rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
54
4.4
Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
54
4.4.1
Storms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
55
4.4.2
Internal heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
55
Orbit and rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
56
4.5.1
Orbital resonances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
56
4.6
Formation and migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
57
4.7
Moons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
57
4.8
Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
58
4.9
Exploration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
58
4.10 See also . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
59
4.11 Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
59
4.12 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
59
4.13 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
64
4.14 Further reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
64
4.15 External links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
64
Saturn
65
5.1
Physical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
65
5.1.1
Internal structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
65
Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
66
5.2.1
Cloud layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
66
5.2.2
North pole hexagonal cloud pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
67
5.2.3
South pole vortex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
67
5.2.4
Other features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
68
5.3
Magnetosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
68
5.4
Orbit and rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
68
5.5
Planetary rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
69
5.6
Natural satellites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
69
5.7
History of exploration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
70
5.7.1
70
4.2
4.5
5
iii
5.2
Ancient observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
iv
6
CONTENTS
5.7.2
European observations (17th–19th centuries) . . . . . . . . . . . . . . . . . . . . . . . . .
70
5.7.3
Modern NASA and ESA probes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
71
5.8
Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
72
5.9
In culture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
73
5.10 See also . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
74
5.11 Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
74
5.12 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
74
5.13 Further reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
78
5.14 External links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
79
Uranus
80
6.1
6.2
6.3
6.4
7
History
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
80
6.1.1
Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
80
6.1.2
Naming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
81
6.1.3
Name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
82
Orbit and rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
82
6.2.1
Axial tilt
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
83
6.2.2
Visibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
83
Internal structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
83
6.3.1
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
84
Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
84
6.4.1
Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
84
6.4.2
Troposphere
85
6.4.3
Upper atmosphere
Internal heat
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
85
6.5
Planetary rings
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
86
6.6
Magnetosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
86
6.7
Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
87
6.7.1
Banded structure, winds and clouds
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
87
6.7.2
Seasonal variation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
88
6.8
Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
89
6.9
Moons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
89
6.10 Exploration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
90
6.11 In culture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
90
6.12 See also . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
91
6.13 Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
91
6.14 References
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
91
6.15 Further reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
96
6.16 External links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
96
Venus
97
7.1
Physical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
97
7.1.1
97
Geography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CONTENTS
v
7.1.2
Surface geology
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
98
7.1.3
Internal structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
99
7.1.4
Atmosphere and climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
99
7.1.5
Magnetic field and core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
7.2
Orbit and rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
7.3
Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
7.4
7.5
7.6
7.3.1
Transits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
7.3.2
Ashen light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Studies
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
7.4.1
Early studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
7.4.2
Ground-based research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
Exploration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
7.5.1
Early efforts
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
7.5.2
Atmospheric entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
7.5.3
Surface and atmospheric science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
7.5.4
Radar mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
7.5.5
Current and future missions
7.5.6
Manned fly-by concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
7.5.7
Sample return . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
7.5.8
Spacecraft timeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
In culture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
7.6.1
Etymology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
7.6.2
Venus symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
7.7
Colonization and terraforming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
7.8
See also . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
7.9
Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
7.10 References
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
7.11 External links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
7.11.1 Cartographic resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
7.12 Text and image sources, contributors, and licenses . . . . . . . . . . . . . . . . . . . . . . . . . . 116
7.12.1 Text . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
7.12.2 Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
7.12.3 Content license . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
Chapter 1
Jupiter
This article is about the planet. For the Roman god, 1.1 Structure
see Jupiter (mythology). For other uses, see Jupiter
(disambiguation).
Jupiter is composed primarily of gaseous and liquid
matter. It is the largest of the four giant planets in the
Jupiter is the fifth planet from the Sun and the largest Solar System and hence its largest planet. It has a diameplanet in the Solar System. It is a giant planet with ter of 142,984 km (88,846 mi) at its equator. The density
a mass one-thousandth of that of the Sun, but is two of Jupiter, 1.326 g/cm3 , is the second highest of the giant
and a half times that of all the other planets in the So- planets, but lower than those of the four terrestrial planlar System combined. Jupiter is a gas giant, along with ets.
Saturn (Uranus and Neptune are ice giants). Jupiter
was known to astronomers of ancient times.* [11] The
Romans named it after their god Jupiter.* [12] When 1.1.1 Composition
viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough to cast shadows,* [13] and Jupiter's upper atmosphere is composed of about 88–
making it on average the third-brightest object in the 92% hydrogen and 8–12% helium by percent volume of
night sky after the Moon and Venus. (Mars can briefly gas molecules. Because a helium atom has about four
match Jupiter's brightness at certain points in its orbit.)
times as much mass as a hydrogen atom, the composiJupiter is primarily composed of hydrogen with a quar- tion changes when described as the proportion of mass
ter of its mass being helium, although helium only com- contributed by different atoms. Thus, the atmosphere is
prises about a tenth of the number of molecules. It may approximately 75% hydrogen and 24% helium by mass,
also have a rocky core of heavier elements,* [14] but like with the remaining one percent of the mass consisting
the other giant planets, Jupiter lacks a well-defined solid of other elements. The interior contains denser materisurface. Because of its rapid rotation, the planet's shape als, such that the distribution is roughly 71% hydrogen,
is that of an oblate spheroid (it has a slight but notice- 24% helium and 5% other elements by mass. The atmoable bulge around the equator). The outer atmosphere sphere contains trace amounts of methane, water vapor,
is visibly segregated into several bands at different lat- ammonia, and silicon-based compounds. There are also
itudes, resulting in turbulence and storms along their in- traces of carbon, ethane, hydrogen sulfide, neon, oxygen,
atteracting boundaries. A prominent result is the Great Red phosphine, and sulfur. The outermost layer *of the
*
mosphere
contains
crystals
of
frozen
ammonia.
[15]
[16]
Spot, a giant storm that is known to have existed since at
least the 17th century when it was first seen by telescope. Through infrared and ultraviolet measurements, trace
Surrounding Jupiter is a faint planetary ring system and a amounts of *benzene and other hydrocarbons have also
powerful magnetosphere. Jupiter has at least 67 moons, been found. [17]
including the four large Galilean moons discovered by The atmospheric proportions of hydrogen and helium are
Galileo Galilei in 1610. Ganymede, the largest of these, close to the theoretical composition of the primordial
has a diameter greater than that of the planet Mercury.
solar nebula. Neon in the upper atmosphere only consists
mass, which is about a tenth as
Jupiter has been explored on several occasions by robotic of 20 parts per million by
*
abundant
as
in
the
Sun.
[18]
Helium is also depleted, to
spacecraft, most notably during the early Pioneer and
about
80%
of
the
Sun's
helium
composition. This depleVoyager flyby missions and later by the Galileo orbiter.
precipitation
of
these elements into the
tion
is
a
result
of
The most recent probe to visit Jupiter was the Pluto*
interior
of
the
planet.
[19]
Abundances
of heavier inert
bound New Horizons spacecraft in late February 2007.
gases
in
Jupiter's
atmosphere
are
about
two
to three times
The probe used the gravity from Jupiter to increase its
that
of
the
Sun.
speed. Future targets for exploration in the Jovian system include the possible ice-covered liquid ocean on the Based on spectroscopy, Saturn is thought to be simimoon Europa.
lar in composition to Jupiter, but the other giant plan1
2
CHAPTER 1. JUPITER
ets Uranus and Neptune have relatively much less hydrogen and helium.* [20] Because of the lack of atmospheric entry probes, high-quality abundance numbers of
the heavier elements are lacking for the outer planets beyond Jupiter.
1.1.2
Mass and size
creasing mass would continue until appreciable stellar ignition is achieved as in high-mass brown dwarfs having
around 50 Jupiter masses.* [27]
Although Jupiter would need to be about 75 times as
massive to fuse hydrogen and become a star, the smallest red dwarf is only about 30 percent larger in radius
than Jupiter.* [28]* [29] Despite this, Jupiter still radiates
more heat than it receives from the Sun; the amount of
heat produced inside it is similar to the total solar radiation it receives.* [30] This additional heat is generated by
the Kelvin–Helmholtz mechanism through contraction.
This process causes Jupiter to shrink by about 2 cm each
year.* [31] When it was first formed, Jupiter was much
hotter and was about twice its current diameter.* [32]
1.1.3 Internal structure
Jupiter's diameter is one order of magnitude smaller (×0.10045)
than the Sun, and one order of magnitude larger (×10.9733)
than the Earth. The Great Red Spot has roughly the same size as
the circumference of the Earth.
Jupiter's mass is 2.5 times that of all the other planets
in the Solar System combined—this is so massive that
its barycenter with the Sun lies above the Sun's surface
at 1.068 solar radii from the Sun's center. Although this
planet dwarfs the Earth with a diameter 11 times as great,
it is considerably less dense. Jupiter's volume is that
of about 1,321 Earths, but it is only 318 times as massive.* [4]* [21] Jupiter's radius is about 1/10 the radius of
the Sun,* [22] and its mass is 0.001 times the mass of the
Sun, so the density of the two bodies is similar.* [23] A
"Jupiter mass" (M J or M Jup ) is often used as a unit to
describe masses of other objects, particularly extrasolar
planets and brown dwarfs. So, for example, the extrasolar
planet HD 209458 b has a mass of 0.69 M J , while Kappa
Andromedae b has a mass of 12.8 M J .* [24]
Theoretical models indicate that if Jupiter had much more
mass than it does at present, it would shrink.* [25] For
small changes in mass, the radius would not change appreciably, and above about 500 M ⊕ (1.6 Jupiter masses)* [25]
the interior would become so much more compressed under the increased pressure that its volume would decrease
despite the increasing amount of matter. As a result,
Jupiter is thought to have about as large a diameter as
a planet of its composition and evolutionary history can
achieve.* [26] The process of further shrinkage with in-
Jupiter is thought to consist of a dense core with a mixture
of elements, a surrounding layer of liquid metallic hydrogen with some helium, and an outer layer predominantly
of molecular hydrogen.* [31] Beyond this basic outline,
there is still considerable uncertainty. The core is often
described as rocky, but its detailed composition is unknown, as are the properties of materials at the temperatures and pressures of those depths (see below). In 1997,
the existence of the core was suggested by gravitational
measurements,* [31] indicating a mass of from 12 to 45
times the Earth's mass or roughly 4%–14% of the total
mass of Jupiter.* [30]* [33] The presence of a core during
at least part of Jupiter's history is suggested by models of
planetary formation that require the formation of a rocky
or icy core massive enough to collect its bulk of hydrogen and helium from the protosolar nebula. Assuming it
did exist, it may have shrunk as convection currents of
hot liquid metallic hydrogen mixed with the molten core
and carried its contents to higher levels in the planetary
interior. A core may now be entirely absent, as gravitational measurements are not yet precise enough to rule
that possibility out entirely.* [31]* [34]
The uncertainty of the models is tied to the error margin
in hitherto measured parameters: one of the rotational
coefficients (J6 ) used to describe the planet's gravitational
moment, Jupiter's equatorial radius, and its temperature
at 1 bar pressure. The Juno mission, which launched in
August 2011, is expected to better constrain the values
of these parameters, and thereby make progress on the
problem of the core.* [35]
The core region is surrounded by dense metallic hydrogen, which extends outward to about 78% of the radius of the planet.* [30] Rain-like droplets of helium and
neon precipitate downward through this layer, depleting the abundance of these elements in the upper atmosphere.* [19]* [36]
Above the layer of metallic hydrogen lies a transparent interior atmosphere of hydrogen. At this depth, the temperature is above the critical temperature, which for hydro-
1.2. ATMOSPHERE
3
gen is only 33 K* [37] (see hydrogen). In this state, there
are no distinct liquid and gas phases—hydrogen is said to
be in a supercritical fluid state. It is convenient to treat
hydrogen as gas in the upper layer extending downward
from the cloud layer to a depth of about 1,000 km,* [30]
and as liquid in deeper layers. Physically, there is no clear
boundary—the gas smoothly becomes hotter and denser
as one descends.* [38]* [39]
The temperature and pressure inside Jupiter increase
steadily toward the core, due to the Kelvin–Helmholtz
mechanism. At the “surface”pressure level of 10 bars,
the temperature is around 340 K (67 °C; 152 °F). At
the phase transition region where hydrogen—heated beyond its critical point—becomes metallic, it is believed
the temperature is 10,000 K (9,700 °C; 17,500 °F) and
the pressure is 200 GPa. The temperature at the core
boundary is estimated to be 36,000 K (35,700 °C; 64,300
°F) and the interior pressure is roughly 3,000–4,500 This view of Jupiter's Great Red Spot and its surroundings was
GPa.* [30]
obtained by Voyager 1 on February 25, 1979, when the spacecraft was 9.2 million km (5.7 million mi) from Jupiter. The white
oval storm directly below the Great Red Spot is approximately the
same diameter as Earth.
color and intensity from year to year, but they have remained sufficiently stable for astronomers to give them
identifying designations.* [21]
This cut-away illustrates a model of the interior of Jupiter, with a
rocky core overlaid by a deep layer of liquid metallic hydrogen.
1.2 Atmosphere
Main article: Atmosphere of Jupiter
This looping animation shows the movement of Jupiter's counterrotating cloud bands. In this image, the planet's exterior is
mapped onto a cylindrical projection. Animation at larger
widths: 720 pixels, 1799 pixels.
The cloud layer is only about 50 km (31 mi) deep, and
consists of at least two decks of clouds: a thick lower
deck and a thin clearer region. There may also be a
thin layer of water clouds underlying the ammonia layer,
as evidenced by flashes of lightning detected in the atmosphere of Jupiter. This is caused by water's polarity,
which makes it capable of creating the charge separation
needed to produce lightning.* [30] These electrical discharges can be up to a thousand times as powerful as light1.2.1 Cloud layers
ning on the Earth.* [43] The water clouds can form thun*
Jupiter is perpetually covered with clouds composed of derstorms driven by the heat rising from the interior. [44]
ammonia crystals and possibly ammonium hydrosulfide. The orange and brown coloration in the clouds of Jupiter
The clouds are located in the tropopause and are ar- are caused by upwelling compounds that change color
ranged into bands of different latitudes, known as tropi- when they are exposed to ultraviolet light from the
cal regions. These are sub-divided into lighter-hued zones Sun. The exact makeup remains uncertain, but the suband darker belts. The interactions of these conflicting stances are believed to be phosphorus, sulfur or possicirculation patterns cause storms and turbulence. Wind bly hydrocarbons.* [30]* [45] These colorful compounds,
speeds of 100 m/s (360 km/h) are common in zonal known as chromophores, mix with the warmer, lower
jets.* [42] The zones have been observed to vary in width, deck of clouds. The zones are formed when rising
Jupiter has the largest planetary atmosphere in the Solar System, spanning over 5,000 km (3,107 mi) in altitude.* [40]* [41] As Jupiter has no surface, the base of its
atmosphere is usually considered to be the point at which
atmospheric pressure is equal to 1 MPa (10 bar), or ten
times surface pressure on Earth.* [40]
4
CHAPTER 1. JUPITER
convection cells form crystallizing ammonia that masks
out these lower clouds from view.* [46]
Jupiter's low axial tilt means that the poles constantly receive less solar radiation than at the planet's equatorial
region. Convection within the interior of the planet transports more energy to the poles, balancing out the temperatures at the cloud layer.* [21]
1.2.2
Great Red Spot and other vortices
Time-lapse sequence (over 1 month) from the approach of
Voyager 1 to Jupiter, showing the motion of atmospheric bands,
and circulation of the Great Red Spot. Full size video here
Jupiter – Great Red Spot is decreasing in size (May 15,
2014).* [47]
The best known feature of Jupiter is the Great Red Spot,
a persistent anticyclonic storm that is larger than Earth,
located 22° south of the equator. Latest evidence by
the Hubble Space Telescope shows there are three “red
spots”adjacent to the Great Red Spot* [48] It is known to
have been in existence since at least 1831,* [49] and possibly since 1665.* [50]* [51] Mathematical models suggest
that the storm is stable and may be a permanent feature
of the planet.* [52] The storm is large enough to be visible through Earth-based telescopes with an aperture of
12 cm or larger.* [53]
times around the planet relative to any possible fixed rotational marker below it.
In 2000, an atmospheric feature formed in the southern hemisphere that is similar in appearance to the Great
Red Spot, but smaller. This was created when several
smaller, white oval-shaped storms merged to form a single feature—these three smaller white ovals were first observed in 1938. The merged feature was named Oval BA,
and has been nicknamed Red Spot Junior. It has since
increased in intensity and changed color from white to
red.* [57]* [58]* [59]
1.3 Planetary rings
The oval object rotates counterclockwise, with a period
of about six days.* [54] The Great Red Spot's dimensions
are 24–40,000 km × 12–14,000 km. It is large enough
to contain two or three planets of Earth's diameter.* [55]
The maximum altitude of this storm is about 8 km (5 mi)
above the surrounding cloudtops.* [56]
Storms such as this are common within the turbulent
atmospheres of giant planets. Jupiter also has white
ovals and brown ovals, which are lesser unnamed storms.
White ovals tend to consist of relatively cool clouds within
the upper atmosphere. Brown ovals are warmer and located within the“normal cloud layer”. Such storms can
last as little as a few hours or stretch on for centuries.
Even before Voyager proved that the feature was a storm,
there was strong evidence that the spot could not be as- The rings of Jupiter
sociated with any deeper feature on the planet's surface,
as the Spot rotates differentially with respect to the rest Main article: Rings of Jupiter
of the atmosphere, sometimes faster and sometimes more
slowly. During its recorded history it has traveled several Jupiter has a faint planetary ring system composed of
1.5. ORBIT AND ROTATION
three main segments: an inner torus of particles known
as the halo, a relatively bright main ring, and an outer
gossamer ring.* [60] These rings appear to be made of
dust, rather than ice as with Saturn's rings.* [30] The main
ring is probably made of material ejected from the satellites Adrastea and Metis. Material that would normally
fall back to the moon is pulled into Jupiter because of its
strong gravitational influence. The orbit of the material
veers towards Jupiter and new material is added by additional impacts.* [61] In a similar way, the moons Thebe
and Amalthea probably produce the two distinct components of the dusty gossamer ring.* [61] There is also evidence of a rocky ring strung along Amalthea's orbit which
may consist of collisional debris from that moon.* [62]
1.4 Magnetosphere
5
magnetosheath—a region between it and the bow shock.
The solar wind interacts with these regions, elongating
the magnetosphere on Jupiter's lee side and extending it
outward until it nearly reaches the orbit of Saturn. The
four largest moons of Jupiter all orbit within the magnetosphere, which protects them from the solar wind.* [30]
The magnetosphere of Jupiter is responsible for intense
episodes of radio emission from the planet's polar regions. Volcanic activity on the Jovian moon Io (see below) injects gas into Jupiter's magnetosphere, producing
a torus of particles about the planet. As Io moves through
this torus, the interaction generates Alfvén waves that
carry ionized matter into the polar regions of Jupiter. As
a result, radio waves are generated through a cyclotron
maser mechanism, and the energy is transmitted out along
a cone-shaped surface. When the Earth intersects this
cone, the radio emissions from Jupiter can exceed the solar radio output.* [64]
Main article: Magnetosphere of Jupiter
Jupiter's magnetic field is 14 times as strong as the
1.5 Orbit and rotation
Aurora on Jupiter. Three bright dots are created by magnetic flux
tubes that connect to the Jovian moons Io (on the left), Ganymede
(on the bottom) and Europa (also on the bottom). In addition, the
very bright almost circular region, called the main oval, and the
fainter polar aurora can be seen.
Earth's, ranging from 4.2 gauss (0.42 mT) at the equator
to 10–14 gauss (1.0–1.4 mT) at the poles, making it the
strongest in the Solar System (except for sunspots).* [46]
This field is believed to be generated by eddy currents
—swirling movements of conducting materials—within
the liquid metallic hydrogen core. The volcanoes on the
moon Io emit large amounts of sulfur dioxide forming
a gas torus along the moon's orbit. The gas is ionized
in the magnetosphere producing sulfur and oxygen ions.
They, together with hydrogen ions originating from the
atmosphere of Jupiter, form a plasma sheet in Jupiter's
equatorial plane. The plasma in the sheet co-rotates
with the planet causing deformation of the dipole magnetic field into that of magnetodisk. Electrons within the
plasma sheet generate a strong radio signature that produces bursts in the range of 0.6–30 MHz.* [63]
At about 75 Jupiter radii from the planet, the interaction of the magnetosphere with the solar wind generates a bow shock. Surrounding Jupiter's magnetosphere is a magnetopause, located at the inner edge of a
Jupiter (red) completes one orbit of the Sun (center) for every
11.86 orbits of the Earth (blue)
Jupiter is the only planet that has a center of mass with
the Sun that lies outside the volume of the Sun, though by
only 7% of the Sun's radius.* [65] The average distance
between Jupiter and the Sun is 778 million km (about
5.2 times the average distance from the Earth to the Sun,
or 5.2 AU) and it completes an orbit every 11.86 years.
This is two-fifths the orbital period of Saturn, forming
a 5:2 orbital resonance between the two largest planets
in the Solar System.* [66] The elliptical orbit of Jupiter
is inclined 1.31° compared to the Earth. Because of
an eccentricity of 0.048, the distance from Jupiter and
the Sun varies by 75 million km between perihelion and
aphelion, or the nearest and most distant points of the
6
CHAPTER 1. JUPITER
planet along the orbital path respectively.
The axial tilt of Jupiter is relatively small: only 3.13°. As
a result this planet does not experience significant seasonal changes, in contrast to Earth and Mars for example.* [67]
Jupiter's rotation is the fastest of all the Solar System's
planets, completing a rotation on its axis in slightly less
than ten hours; this creates an equatorial bulge easily seen
through an Earth-based amateur telescope. The planet is
shaped as an oblate spheroid, meaning that the diameter
across its equator is longer than the diameter measured
between its poles. On Jupiter, the equatorial diameter is The retrograde motion of an outer planet is caused by its relative
9,275 km (5,763 mi) longer than the diameter measured location with respect to the Earth.
through the poles.* [39]
Because Jupiter is not a solid body, its upper atmosphere
undergoes differential rotation. The rotation of Jupiter's
polar atmosphere is about 5 minutes longer than that
of the equatorial atmosphere; three systems are used as
frames of reference, particularly when graphing the motion of atmospheric features. System I applies from the
latitudes 10° N to 10° S; its period is the planet's shortest,
at 9h 50m 30.0s. System II applies at all latitudes north
and south of these; its period is 9h 55m 40.6s. System III
was first defined by radio astronomers, and corresponds
to the rotation of the planet's magnetosphere; its period
is Jupiter's official rotation.* [68]
1.6 Observation
Earth overtakes Jupiter every 398.9 days as it orbits the
Sun, a duration called the synodic period. As it does
so, Jupiter appears to undergo retrograde motion with respect to the background stars. That is, for a period Jupiter
seems to move backward in the night sky, performing a
looping motion.
Jupiter's 12-year orbital period corresponds to the dozen
astrological signs of the zodiac, and may have been the
historical origin of the signs.* [21] That is, each time
Jupiter reaches opposition it has advanced eastward by
about 30°, the width of a zodiac sign.
Because the orbit of Jupiter is outside the Earth's, the
phase angle of Jupiter as viewed from the Earth never
exceeds 11.5°. That is, the planet always appears nearly
fully illuminated when viewed through Earth-based telescopes. It was only during spacecraft missions to Jupiter
that crescent views of the planet were obtained.* [70] A
small telescope will usually show Jupiter's four Galilean
moons and the prominent cloud belts across Jupiter's
atmosphere.* [71] A large telescope will show Jupiter's
Great Red Spot when it faces the Earth.
1.7 Research and exploration
1.7.1 Pre-telescopic research
Conjunction of Jupiter and the Moon
Jupiter is usually the fourth brightest object in the sky
(after the Sun, the Moon and Venus);* [46] at times Mars
appears brighter than Jupiter. Depending on Jupiter's
position with respect to the Earth, it can vary in visual
magnitude from as bright as −2.9 at opposition down to
−1.6 during conjunction with the Sun. The angular diameter of Jupiter likewise varies from 50.1 to 29.8 arc
seconds.* [4] Favorable oppositions occur when Jupiter is
passing through perihelion, an event that occurs once per
orbit. As Jupiter approached perihelion in March 2011,
there was a favorable opposition in September 2010.* [69]
The observation of Jupiter dates back to the Babylonian
astronomers of the 7th or 8th century BC.* [72] The Chinese historian of astronomy, Xi Zezong, has claimed that
Gan De, a Chinese astronomer, made the discovery of
one of Jupiter's moons in 362 BC with the unaided eye.
If accurate, this would predate Galileo's discovery by
nearly two millennia.* [73]* [74] In his 2nd century work
the Almagest, the Hellenistic astronomer Claudius Ptolemaeus constructed a geocentric planetary model based on
deferents and epicycles to explain Jupiter's motion relative to the Earth, giving its orbital period around the Earth
as 4332.38 days, or 11.86 years.* [75] In 499, Aryabhata,
a mathematician–astronomer from the classical age of
Indian mathematics and astronomy, also used a geocen-
1.7. RESEARCH AND EXPLORATION
7
M
ϕ
R
e
e
r
θ
A
Model in the Almagest of the longitudinal motion of Jupiter ( )
relative to the Earth ( ).
False-color detail of Jupiter's atmosphere, imaged by Voyager 1,
showing the Great Red Spot and a passing white oval.
the Earth, these events would occur about 17 minutes
tric model to estimate Jupiter's period as 4332.2722 days,
later than expected. Ole Rømer deduced that sight is not
*
or 11.86 years. [76]
instantaneous (a conclusion that Cassini had earlier rejected),* [16] and this timing discrepancy was used to estimate the speed of light.* [80]
1.7.2
Ground-based telescope research
In 1610, Galileo Galilei discovered the four largest
moons of Jupiter—Io, Europa, Ganymede and Callisto
(now known as the Galilean moons)—using a telescope;
thought to be the first telescopic observation of moons
other than Earth's. Galileo's was also the first discovery
of a celestial motion not apparently centered on the Earth.
It was a major point in favor of Copernicus' heliocentric
theory of the motions of the planets; Galileo's outspoken
support of the Copernican theory placed him under the
threat of the Inquisition.* [77]
In 1892, E. E. Barnard observed a fifth satellite of Jupiter
with the 36-inch (910 mm) refractor at Lick Observatory in California. The discovery of this relatively small
object, a testament to his keen eyesight, quickly made
him famous. This moon was later named Amalthea.* [81]
It was the last planetary moon to be discovered directly
by visual observation.* [82] An additional eight satellites
were discovered before the flyby of the Voyager 1 probe
in 1979.
During the 1660s, Cassini used a new telescope to discover spots and colorful bands on Jupiter and observed
that the planet appeared oblate; that is, flattened at the
poles. He was also able to estimate the rotation period of
the planet.* [16] In 1690 Cassini noticed that the atmosphere undergoes differential rotation.* [30]
The Great Red Spot, a prominent oval-shaped feature in
the southern hemisphere of Jupiter, may have been observed as early as 1664 by Robert Hooke and in 1665 by
Giovanni Cassini, although this is disputed. The pharmacist Heinrich Schwabe produced the earliest known drawing to show details of the Great Red Spot in 1831.* [78]
The Red Spot was reportedly lost from sight on several
occasions between 1665 and 1708 before becoming quite
conspicuous in 1878. It was recorded as fading again in
1883 and at the start of the 20th century.* [79]
Infrared image of Jupiter taken by ESO's Very Large Telescope.
Both Giovanni Borelli and Cassini made careful tables
of the motions of the Jovian moons, allowing predicof amtions of the times when the moons would pass before or In 1932, Rupert Wildt identified absorption bands
*
[83]
monia
and
methane
in
the
spectra
of
Jupiter.
behind the planet. By the 1670s, it was observed that
when Jupiter was on the opposite side of the Sun from Three long-lived anticyclonic features termed white ovals
8
CHAPTER 1. JUPITER
were observed in 1938. For several decades they remained as separate features in the atmosphere, sometimes
approaching each other but never merging. Finally, two
of the ovals merged in 1998, then absorbed the third in
2000, becoming Oval BA.* [84]
1.7.3
Radiotelescope research
In 1955, Bernard Burke and Kenneth Franklin detected
bursts of radio signals coming from Jupiter at 22.2
MHz.* [30] The period of these bursts matched the rotation of the planet, and they were also able to use this
information to refine the rotation rate. Radio bursts from
Jupiter were found to come in two forms: long bursts (or
L-bursts) lasting up to several seconds, and short bursts
(or S-bursts) that had a duration of less than a hundredth
of a second.* [85]
Scientists discovered that there were three forms of radio
signals transmitted from Jupiter.
• Decametric radio bursts (with a wavelength of tens
of meters) vary with the rotation of Jupiter, and are
influenced by interaction of Io with Jupiter's magnetic field.* [86]
• Decimetric radio emission (with wavelengths measured in centimeters) was first observed by Frank
Drake and Hein Hvatum in 1959.* [30] The origin of this signal was from a torus-shaped belt
around Jupiter's equator. This signal is caused by
cyclotron radiation from electrons that are accelerated in Jupiter's magnetic field.* [87]
Flyby missions
Beginning in 1973, several spacecraft have performed
planetary flyby maneuvers that brought them within observation range of Jupiter. The Pioneer missions obtained the first close-up images of Jupiter's atmosphere
and several of its moons. They discovered that the radiation fields near the planet were much stronger than expected, but both spacecraft managed to survive in that
environment. The trajectories of these spacecraft were
used to refine the mass estimates of the Jovian system.
Radio occultations by the planet resulted in better measurements of Jupiter's diameter and the amount of polar
flattening.* [21]* [94]
Six years later, the Voyager missions vastly improved
the understanding of the Galilean moons and discovered
Jupiter's rings. They also confirmed that the Great Red
Spot was anticyclonic. Comparison of images showed
that the Red Spot had changed hue since the Pioneer missions, turning from orange to dark brown. A torus of
ionized atoms was discovered along Io's orbital path, and
volcanoes were found on the moon's surface, some in the
process of erupting. As the spacecraft passed behind the
planet, it observed flashes of lightning in the night side
atmosphere.* [15]* [21]
The next mission to encounter Jupiter, the Ulysses solar
probe, performed a flyby maneuver to attain a polar orbit around the Sun. During this pass the spacecraft conducted studies on Jupiter's magnetosphere. Since Ulysses
has no cameras, no images were taken. A second flyby
six years later was at a much greater distance.* [93]
• Thermal radiation is produced by heat in the atmosphere of Jupiter.* [30]
1.7.4
Exploration with space probes
Main article: Exploration of Jupiter
Since 1973 a number of automated spacecraft have visited Jupiter, most notably the Pioneer 10 space probe, the
first spacecraft to get close enough to Jupiter to send back
revelations about the properties and phenomena of the
Solar System's largest planet.* [88]* [89] Flights to other
planets within the Solar System are accomplished at a cost
in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Entering a Hohmann
transfer orbit from Earth to Jupiter from low Earth orbit requires a delta-v of 6.3 km/s* [90] which is comparable to the 9.7 km/s delta-v needed to reach low Earth
orbit.* [91] Fortunately, gravity assists through planetary
flybys can be used to reduce the energy required to reach
Jupiter, albeit at the cost of a significantly longer flight
duration.* [92]
Cassini views Jupiter and Io on January 1, 2001
In 2000, the Cassini probe, en route to Saturn, flew by
Jupiter and provided some of the highest-resolution images ever made of the planet. On December 19, 2000, the
spacecraft captured an image of the moon Himalia, but
the resolution was too low to show surface details.* [95]
1.8. MOONS
The New Horizons probe, en route to Pluto, flew by
Jupiter for gravity assist. Its closest approach was on
February 28, 2007.* [96] The probe's cameras measured
plasma output from volcanoes on Io and studied all
four Galilean moons in detail, as well as making longdistance observations of the outer moons Himalia and
Elara.* [97] Imaging of the Jovian system began September 4, 2006.* [98]* [99]
9
times Earth normal, at a temperature of 153 °C).* [101]
It would have melted thereafter, and possibly vaporized.
The Galileo orbiter itself experienced a more rapid version of the same fate when it was deliberately steered into
the planet on September 21, 2003, at a speed of over 50
km/s, to avoid any possibility of it crashing into and possibly contaminating Europa—a moon which has been hypothesized to have the possibility of harboring life.* [100]
Data from this mission revealed that hydrogen composes
up to 90% of Jupiter's atmosphere.* [26] The temperaGalileo mission
tures data recorded was more than 300 °C (>570 °F)
and the windspeed measured more than 644 kmph (>400
Main article: Galileo (spacecraft)
*
So far the only spacecraft to orbit Jupiter is the Galileo or- mph) before the probes vapourised. [26]
Future probes
NASA has a mission underway to study Jupiter in detail
from a polar orbit. Named Juno, the spacecraft launched
in August 2011, and will arrive in late 2016.* [102] The
next planned mission to the Jovian system will be the
European Space Agency's Jupiter Icy Moon Explorer
(JUICE), due to launch in 2022.* [103]
Canceled missions
Because of the possibility of subsurface liquid oceans
on Jupiter's moons Europa, Ganymede and Callisto,
there has been great interest in studying the icy moons
in detail. Funding difficulties have delayed progress.
NASA's JIMO (Jupiter Icy Moons Orbiter) was cancelled in 2005.* [104] A subsequent proposal for a joint
NASA/ESA mission, called EJSM/Laplace, was developed with a provisional launch date around 2020.
EJSM/Laplace would have consisted of the NASAled Jupiter Europa Orbiter, and the ESA-led Jupiter
Ganymede Orbiter.* [105] However by April 2011, ESA
had formally ended the partnership citing budget issues
at NASA and the consequences on the mission timetable.
Jupiter as seen by the space probe Cassini.
Instead ESA planned to go ahead with a Europeanonly mission to compete in its L1 Cosmic Vision selecbiter, which went into orbit around Jupiter on December tion.* [106]
7, 1995.* [26] It orbited the planet for over seven years,
conducting multiple flybys of all the Galilean moons and
Amalthea. The spacecraft also witnessed the impact of
Comet Shoemaker–Levy 9 as it approached Jupiter in 1.8 Moons
1994, giving a unique vantage point for the event. While
the information gained about the Jovian system from Main article: Moons of Jupiter
Galileo was extensive, its originally designed capacity was See also: Timeline of discovery of Solar System planets
limited by the failed deployment of its high-gain radio and their moons
transmitting antenna.* [100]
A 340-kilogram titanium atmospheric probe was released
from the spacecraft in July 1995, entering Jupiter's atmosphere on December 7.* [26] It parachuted through
150 km (93 mi) of the atmosphere at speed of about
2,575 km/h (1600 mph)* [26] and collected data for 57.6
minutes before it was crushed by the pressure (about 23
Jupiter has 67 natural satellites.* [107] Of these, 51 are
less than 10 kilometres in diameter and have only been
discovered since 1975. The four largest moons, visible
from Earth with binoculars on a clear night, known as the
"Galilean moons", are Io, Europa, Ganymede and Callisto.
10
CHAPTER 1. JUPITER
is seen most dramatically in the extraordinary volcanic
activity of innermost Io (which is subject to the strongest
tidal forces), and to a lesser degree in the geological youth
of Europa's surface (indicating recent resurfacing of the
moon's exterior).
1.8.2 Classification of moons
Jupiter with the Galilean moons. Seen from Earth at this point in
their orbits, Europa appears closer to Jupiter than does Io.
Jupiter's moon Europa.
1.8.1
Galilean moons
Before the discoveries of the Voyager missions, Jupiter's
moons were arranged neatly into four groups of four,
Main article: Galilean moons
The orbits of Io, Europa, and Ganymede, some of based on commonality of their orbital elements. Since
then, the large number of new small outer moons has
complicated this picture. There are now thought to be
six main groups, although some are more distinct than
others.
A basic sub-division is a grouping of the eight inner regular moons, which have nearly circular orbits near the
plane of Jupiter's equator and are believed to have formed
with Jupiter. The remainder of the moons consist of an
The Galilean moons. From left to right, in order of increasing unknown number of small irregular moons with elliptidistance from Jupiter: Io, Europa, Ganymede, Callisto.
cal and inclined orbits, which are believed to be captured
asteroids or fragments of captured asteroids. Irregular
the largest satellites in the Solar System, form a pattern moons that belong to a group share similar orbital eleknown as a Laplace resonance; for every four orbits that ments and thus may have a common origin, perhaps as a
Io makes around Jupiter, Europa makes exactly two orbits larger moon or captured body that broke up.* [109]* [110]
and Ganymede makes exactly one. This resonance causes
the gravitational effects of the three large moons to distort their orbits into elliptical shapes, since each moon
receives an extra tug from its neighbors at the same point 1.9 Interaction with the Solar Sysin every orbit it makes. The tidal force from Jupiter, on
tem
the other hand, works to circularize their orbits.* [108]
The eccentricity of their orbits causes regular flexing of
the three moons' shapes, with Jupiter's gravity stretching
them out as they approach it and allowing them to spring
back to more spherical shapes as they swing away. This
tidal flexing heats the moons' interiors by friction. This
Along with the Sun, the gravitational influence of Jupiter
has helped shape the Solar System. The orbits of most
of the system's planets lie closer to Jupiter's orbital plane
than the Sun's equatorial plane (Mercury is the only planet
that is closer to the Sun's equator in orbital tilt), the
1.9. INTERACTION WITH THE SOLAR SYSTEM
11
Kirkwood gaps in the asteroid belt are mostly caused by
Jupiter, and the planet may have been responsible for the
Late Heavy Bombardment of the inner Solar System's
history.* [112]
Hubble image taken on July 23 showing a blemish of about 5,000
miles long left by the 2009 Jupiter impact.* [115]
numbers that it accretes or ejects them.* [118] This topic
remains controversial among astronomers, as some believe it draws comets towards Earth from the Kuiper belt
Along with its moons, Jupiter's gravitational field con- while others believe* that Jupiter protects Earth from the
trols numerous asteroids that have settled into the re- alleged Oort cloud. [119] Jupiter experiences about* 200
gions of the Lagrangian points preceding and following times more asteroid and comet impacts than Earth. [26]
Jupiter in its orbit around the Sun. These are known A 1997 survey of historical astronomical drawings sugas the Trojan asteroids, and are divided into Greek and gested that the astronomer Cassini may have recorded an
Trojan “camps”to commemorate the Iliad. The first impact scar in 1690. The survey determined eight other
of these, 588 Achilles, was discovered by Max Wolf in candidate observations had low or no possibilities of an
1906; since then more than two thousand have been dis- impact.* [120] A fireball was photographed by Voyager 1
covered.* [113] The largest is 624 Hektor.
during its Jupiter encounter in March 1979.* [121] During
Most short-period comets belong to the Jupiter family the period July 16, 1994, to July 22, 1994, over 20 frag—defined as comets with semi-major axes smaller than ments from the comet Shoemaker–Levy 9 (SL9, formally
Jupiter's. Jupiter family comets are believed to form in designated D/1993 F2) collided with Jupiter's southern
the Kuiper belt outside the orbit of Neptune. During close hemisphere, providing the first direct observation of a
encounters with Jupiter their orbits are perturbed into a collision between two Solar System objects. This impact
data on the composition of Jupiter's atsmaller period and then circularized by regular gravita- provided useful
*
*
mosphere.
[122]
[123]
tional interaction with the Sun and Jupiter.* [114]
This diagram shows the Trojan asteroids in Jupiter's orbit, as well
as the main asteroid belt.
On July 19, 2009, an impact site was discovered
at approximately 216 degrees longitude in System
1.9.1 Impacts
2.* [124]* [125] This impact left behind a black spot in
Jupiter's atmosphere, similar in size to Oval BA. Infrared
See also: Comet Shoemaker–Levy 9, 2009 Jupiter im- observation showed a bright spot where the impact took
pact event and 2010 Jupiter impact event
place, meaning the impact warmed up the lower atmoJupiter has been called the Solar System's vacuum sphere in the area near Jupiter's south pole.* [126]
cleaner,* [116] because of its immense gravity well and
location near the inner Solar System. It receives the A fireball, smaller than the previous observed impacts,
most frequent comet impacts of the Solar System's plan- was detected on June 3, 2010, by Anthony Wesley, an
ets.* [117] It was thought that the planet served to par- amateur astronomer in Australia, and was later discovtially shield the inner system from cometary bombard- ered to have been captured on*video by another amateur
ment.* [26] Recent computer simulations suggest that astronomer in the Philippines.* [127] Yet another fireball
Jupiter does not cause a net decrease in the number of was seen on August 20, 2010. [128]
comets that pass through the inner Solar System, as its On September 10, 2012, another fireball was degravity perturbs their orbits inward in roughly the same tected.* [121]* [129]
12
CHAPTER 1. JUPITER
1.10 Possibility of life
planet along the ecliptic to define the constellations of
their zodiac.* [21]* [134]
Further information: Extraterrestrial life
The Romans named it after Jupiter (Latin: Iuppiter, Iūpiter) (also called Jove), the principal god of Roman
mythology, whose name comes from the Proto-IndoEuropean vocative compound *Dyēu-pəter (nominative:
*Dyēus-pətēr, meaning “O Father Sky-God”, or “O
Father Day-God”).* [135] In turn, Jupiter was the counterpart to the mythical Greek Zeus (Ζεύς), also referred
to as Dias (Δίας), the planetary name of which is retained
in modern Greek.* [136]
In 1953, the Miller–Urey experiment demonstrated that
a combination of lightning and the chemical compounds
that existed in the atmosphere of a primordial Earth could
form organic compounds (including amino acids) that
could serve as the building blocks of life. The simulated atmosphere included water, methane, ammonia and
molecular hydrogen; all molecules still found in the atmosphere of Jupiter. The atmosphere of Jupiter has a
strong vertical air circulation, which would carry these
compounds down into the lower regions. The higher temperatures within the interior of the atmosphere breaks
down these chemicals, which would hinder the formation
of Earth-like life.* [130]
The astronomical symbol for the planet, , is a stylized
representation of the god's lightning bolt. The original
Greek deity Zeus supplies the root zeno-, used to form
some Jupiter-related words, such as zenographic.* [137]
Jovian is the adjectival form of Jupiter. The older adjectival form jovial, employed by astrologers in the Middle
It is considered highly unlikely that there is any Earth- Ages, has come to mean “happy”or “merry,”moods
like life on Jupiter, as there is only a small amount of wa- ascribed to Jupiter's astrological influence.* [138]
ter in the atmosphere and any possible solid surface deep
within Jupiter would be under extraordinary pressures. In The Chinese, Korean and Japanese referred to the planet
pinyin: mùxīng),
1976, before the Voyager missions, it was hypothesized as the “wood star”(Chinese: 木星;
*
based
on
the
Chinese
Five
Elements.
[139]
Chinese Taothat ammonia or water-based life could evolve in Jupiter's
ism
personified
it
as
the
Fu
star.
The
Greeks
called
upper atmosphere. This hypothesis is based on the ecolit
Φαέθων,
Phaethon,
“blazing.”In
Vedic
Astrology,
ogy of terrestrial seas which have simple photosynthetic
plankton at the top level, fish at lower levels feeding on Hindu astrologers named the planet after Brihaspati, the
these creatures, and marine predators which hunt the religious teacher of the gods, and often *called it "Guru",
which literally means the“Heavy One.”[140] In the Enfish.* [131]* [132]
glish language, Thursday is derived from “Thor's day”,
The possible presence of underground oceans on some of with Thor associated with the planet Jupiter in Germanic
Jupiter's moons has led to speculation that the presence mythology.* [141]
of life is more likely there.
In the Central Asian-Turkic myths, Jupiter called as a
“Erendiz/Erentüz”, which means“eren(?)+yultuz(star)".
There are many theories about meaning of“eren”. Also,
1.11 Mythology
these peoples calculated the period of the orbit of Jupiter
as 11 years and 300 days. They believed that some social
and natural events connected to Erentüz's movements on
the sky.* [142]
1.12 See also
• Hot Jupiter
• Jovian–Plutonian gravitational effect
• Jovian (fiction)
Jupiter, woodcut from a 1550 edition of Guido Bonatti's Liber
Astronomiae.
The planet Jupiter has been known since ancient times. It
is visible to the naked eye in the night sky and can occasionally be seen in the daytime when the Sun is low.* [133]
To the Babylonians, this object represented their god
Marduk. They used the roughly 12-year orbit of this
• Juno (spacecraft)
• Jupiter in fiction
• Space exploration
• New Horizons
1.14. REFERENCES
1.13 Notes
[1] Orbital elements refer to the barycenter of the Jupiter system, and are the instantaneous osculating values at the
precise J2000 epoch. Barycenter quantities are given because, in contrast to the planetary centre, they do not experience appreciable changes on a day-to-day basis due to
the motion of the moons.
[2] Refers to the level of 1 bar atmospheric pressure
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18
1.15 Further reading
• Bagenal, F.; Dowling, T. E.; McKinnon, W. B., eds.
(2004). Jupiter: The planet, satellites, and magnetosphere. Cambridge: Cambridge University Press.
ISBN 0-521-81808-7.
• Beebe, Reta (1997). Jupiter: The Giant Planet (Second ed.). Washington, D.C.: Smithsonian Institution Press. ISBN 1-56098-731-6.
1.16 External links
• Hans Lohninger et al. (November 2, 2005).
“Jupiter, As Seen By Voyager 1”. A Trip into
Space. Virtual Institute of Applied Science. Retrieved March 9, 2007.
• Dunn, Tony (2006).“The Jovian System”. Gravity
Simulator. Retrieved March 9, 2007.—A simulation
of the 62 Jovian moons.
• Seronik, G.; Ashford, A. R. “Chasing the Moons
of Jupiter”. Sky & Telescope. Archived from the
original on July 13, 2007. Retrieved March 9, 2007.
• Anonymous (May 2, 2007). “In Pictures: New
views of Jupiter”. BBC News. Retrieved May 2,
2007.
• Cain, Fraser.“Jupiter”. Universe Today. Retrieved
April 1, 2008.
• “Fantastic Flyby of the New Horizons spacecraft
(May 1, 2007.)". NASA. Retrieved May 21, 2008.
• “Moons of Jupiter articles in Planetary Science Research Discoveries”. Planetary Science Research
Discoveries. University of Hawaii, NASA.
• June 2010 impact video
• Bauer, Amanda; Merrifield, Michael (2009).
“Jupiter”. Sixty Symbols. Brady Haran for the
University of Nottingham.
CHAPTER 1. JUPITER
Chapter 2
Mars
This article is about the planet. For other uses, see Mars
(disambiguation).
Mars is the fourth planet from the Sun and the second smallest planet in the Solar System, after Mercury.
Named after the Roman god of war, it is often referred
to as the “Red Planet”because the iron oxide prevalent
on its surface gives it a reddish appearance.* [15] Mars
is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of
the Moon and the volcanoes, valleys, deserts, and polar
ice caps of Earth. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, as
is the tilt that produces the seasons. Mars is the site of
Olympus Mons, largest volcano* [16] and second-highest
known mountain in the Solar System and the tallest on
a planet, and of Valles Marineris, one of the largest
canyons in the Solar System. The smooth Borealis basin
in the northern hemisphere covers 40% of the planet and
may be a giant impact feature.* [17]* [18] Mars has two
moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids,* [19]* [20]
similar to 5261 Eureka, a Mars trojan.
Until the first successful Mars flyby in 1965 by Mariner
4, many speculated about the presence of liquid water on
the planet's surface. This was based on observed periodic variations in light and dark patches, particularly in
the polar latitudes, which appeared to be seas and continents; long, dark striations were interpreted by some as
irrigation channels for liquid water. These straight line
features were later explained as optical illusions, though
geological evidence gathered by unmanned missions suggests that Mars once had large-scale water coverage on
its surface at some earlier stage of its life.* [21] In 2005,
radar data revealed the presence of large quantities of water ice at the poles* [22] and at mid-latitudes.* [23]* [24]
The Mars rover Spirit sampled chemical compounds containing water molecules in March 2007. The Phoenix lander directly sampled water ice in shallow Martian soil on
July 31, 2008.* [25]
Mars is host to seven functioning spacecraft: five in orbit—2001 Mars Odyssey, Mars Express, Mars Reconnaissance Orbiter, MAVEN and Mars Orbiter Mission—and
two on the surface—Mars Exploration Rover Opportunity
and the Mars Science Laboratory Curiosity. Defunct
spacecraft on the surface include MER-A Spirit and several other inert landers and rovers such as the Phoenix
lander, which completed its mission in 2008. Observations by the Mars Reconnaissance Orbiter have revealed
possible flowing water during the warmest months on
Mars.* [26] In 2013, NASA's Curiosity rover discovered
that Mars's soil contains between 1.5% and 3% water by
mass (about two pints of water per cubic foot or 33 liters
per cubic meter, albeit attached to other compounds and
thus not freely accessible).* [27]
Mars can easily be seen from Earth with the naked eye, as
can its reddish coloring. Its apparent magnitude reaches
−3.0,* [10] which is surpassed only by Jupiter, Venus, the
Moon, and the Sun. Optical ground-based telescopes are
typically limited to resolving features about 300 kilometers (190 mi) across when Earth and Mars are closest because of Earth's atmosphere.* [28]
2.1 Physical characteristics
Earth compared with Mars.
Mars - animation (00:40) showing major features.
Mars has approximately half the diameter of Earth. It is
less dense than Earth, having about 15% of Earth's volume and 11% of the mass. Its surface area is only slightly
less than the total area of Earth's dry land.* [6] Although
Mars is larger and more massive than Mercury, Mercury
has a higher density. This results in the two planets having a nearly identical gravitational pull at the surface—
19
20
CHAPTER 2. MARS
that of Mars is stronger by less than 1%. The red-orange
appearance of the Martian surface is caused by iron(III)
oxide, more commonly known as hematite, or rust.* [29]
It can also look like butterscotch,* [30] and other common
surface colors include golden, brown, tan, and greenish,
depending on minerals.* [30]
2.1.1
Internal structure
Like Earth, Mars has differentiated into a dense metallic
core overlaid by less dense materials.* [31] Current models of its interior imply a core region about 1,794 ± 65
kilometers (1,115 ± 40 mi) in radius, consisting primarily of iron and nickel with about 16–17% sulfur.* [32]
This iron(II) sulfide core is thought to be twice as rich
in lighter elements than Earth's core.* [33] The core is
surrounded by a silicate mantle that formed many of the
tectonic and volcanic features on the planet, but it now
appears to be dormant. Besides silicon and oxygen, the
most abundant elements in the Martian crust are iron,
magnesium, aluminum, calcium, and potassium. The average thickness of the planet's crust is about 50 km (31
mi), with a maximum thickness of 125 km (78 mi).* [33]
Earth's crust, averaging 40 km (25 mi), is only one third
as thick as Mars's crust, relative to the sizes of the two
planets. The InSight lander planned for 2016 will use a
seismometer to better constrain the models of the interior.* [34]
Geologic Map of Mars (USGS; July 14, 2014)
(full map / video)* [39]* [40]* [41]
that these bands demonstrate plate tectonics on Mars four
billion years ago, before the planetary dynamo ceased to
function and the planet's magnetic field faded away.* [43]
During the Solar System's formation, Mars was created
as the result of a stochastic process of run-away accretion
out of the protoplanetary disk that orbited the Sun. Mars
has many distinctive chemical features caused by its po2.1.2 Surface geology
sition in the Solar System. Elements with comparatively
low boiling points, such as chlorine, phosphorus, and sulMain article: Geology of Mars
phur, are much more common on Mars than Earth; these
elements were probably removed from areas closer to the
Mars is a terrestrial planet that consists of minerals conSun by the young star's energetic solar wind.* [44]
taining silicon and oxygen, metals, and other elements
that typically make up rock. The surface of Mars is After the formation of the planets, all were subjected to
primarily composed of tholeiitic basalt,* [35] although the so-called "Late Heavy Bombardment". About 60%
parts are more silica-rich than typical basalt and may be of the surface of Mars shows a record of impacts from
*
*
*
similar to andesitic rocks on Earth or silica glass. Re- that era, [45] [46] [47] whereas much of the remaining
gions of low albedo show concentrations of plagioclase surface is probably underlain by immense impact basins
feldspar, with northern low albedo regions displaying caused by those events. There is evidence of an enormous
higher than normal concentrations of sheet silicates and impact basin in the northern hemisphere of Mars, spanhigh-silicon glass. Parts of the southern highlands in- ning 10,600 by 8,500 km (6,600 by 5,300 mi), or roughly
clude detectable amounts of high-calcium pyroxenes. Lo- four times larger than the Moon's South Pole – Aitken
*
*
calized concentrations of hematite and olivine have also basin, the largest impact basin yet discovered. [17] [18]
*
This
theory
suggests
that
Mars
was
struck
by
a
Pluto-sized
been found. [36] Much of the surface is deeply covered
body about four billion years ago. The event, thought to
by finely grained iron(III) oxide dust.* [37]* [38]
be the cause of the Martian hemispheric dichotomy, creAlthough Mars has no evidence of a current structured
ated
the smooth Borealis basin that covers 40% of the
global magnetic field,* [42] observations show that parts
planet.* [48]* [49]
of the planet's crust have been magnetized, and that alternating polarity reversals of its dipole field have occurred The geological history of Mars can be split into many
in the past. This paleomagnetism of magnetically sus- periods, but the following are the three primary peri*
*
ceptible minerals has properties that are similar to the ods: [50] [51]
alternating bands found on the ocean floors of Earth. One
• Noachian period (named after Noachis Terra):
theory, published in 1999 and re-examined in October
Formation of the oldest extant surfaces of Mars, 4.5
2005 (with the help of the Mars Global Surveyor), is
2.1. PHYSICAL CHARACTERISTICS
billion years ago to 3.5 billion years ago. Noachian
age surfaces are scarred by many large impact
craters. The Tharsis bulge, a volcanic upland, is
thought to have formed during this period, with extensive flooding by liquid water late in the period.
• Hesperian period (named after Hesperia Planum):
3.5 billion years ago to 2.9–3.3 billion years ago.
The Hesperian period is marked by the formation
of extensive lava plains.
21
has a basic pH of 7.7, and contains 0.6% of the salt
perchlorate.* [55]* [56]* [57]* [58]
Streaks are common across Mars and new ones appear
frequently on steep slopes of craters, troughs, and valleys. The streaks are dark at first and get lighter with
age. Sometimes, the streaks start in a tiny area which then
spread out for hundreds of metres. They have also been
seen to follow the edges of boulders and other obstacles
in their path. The commonly accepted theories include
that they are dark underlying layers of soil revealed after
avalanches of bright dust or dust devils.* [59] Several explanations have been put forward, some of which involve
water or even the growth of organisms.* [60]* [61]
• Amazonian period (named after Amazonis Planitia): 2.9–3.3 billion years ago to present. Amazonian regions have few meteorite impact craters, but
are otherwise quite varied. Olympus Mons formed
during this period, along with lava flows elsewhere
on Mars.
2.1.4
Hydrology
Some geological activity is still taking place on Mars. Main article: Water on Mars
The Athabasca Valles is home to sheet-like lava flows up Liquid water cannot exist on the surface of Mars due to
to about 200 Mya. Water flows in the grabens called
the Cerberus Fossae occurred less than 20 Mya, indicating equally recent volcanic intrusions.* [52] On February 19, 2008, images from the Mars Reconnaissance Orbiter showed evidence of an avalanche from a 700 m high
cliff.* [53]
2.1.3
Soil
Main article: Martian soil
The Phoenix lander returned data showing Martian soil
Photomicrograph taken by Opportunity showing a gray hematite
concretion, indicative of the past presence of liquid water
low atmospheric pressure, which is about 100 times thinner than Earth's,* [62] except at the lowest elevations for
short periods.* [63]* [64] The two polar ice caps appear to
be made largely of water.* [65]* [66] The volume of water
ice in the south polar ice cap, if melted, would be sufficient to cover the entire planetary surface to a depth of 11
meters (36 ft).* [67] A permafrost mantle stretches from
the pole to latitudes of about 60°.* [65]
Exposure of silica-rich dust uncovered by the Spirit rover
to be slightly alkaline and containing elements such as
magnesium, sodium, potassium and chlorine. These
nutrients are found in gardens on Earth, and they are
necessary for growth of plants.* [54] Experiments performed by the lander showed that the Martian soil
Large quantities of water ice are thought to be trapped
within the thick cryosphere of Mars. Radar data
from Mars Express and the Mars Reconnaissance Orbiter show large quantities of water ice both at the poles
(July 2005)* [22]* [68] and at middle latitudes (November
2008).* [23] The Phoenix lander directly sampled water
ice in shallow Martian soil on July 31, 2008.* [25]
22
Landforms visible on Mars strongly suggest that liquid water has existed on the planet's surface. Huge
linear swathes of scoured ground, known as outflow
channels, cut across the surface in around 25 places.
These are thought to record erosion which occurred during the catastrophic release of water from subsurface
aquifers, though some of these structures have also been
hypothesized to result from the action of glaciers or
lava.* [69]* [70] One of the larger examples, Ma'adim
Vallis is 700 km (430 mi) long and much bigger than the
Grand Canyon with a width of 20 km (12 mi) and a depth
of 2 km (1.2 mi) in some places. It is thought to have been
carved by flowing water early in Mars's history.* [71] The
youngest of these channels are thought to have formed
as recently as only a few million years ago.* [72] Elsewhere, particularly on the oldest areas of the Martian surface, finer-scale, dendritic networks of valleys are spread
across significant proportions of the landscape. Features
of these valleys and their distribution strongly imply that
they were carved by runoff resulting from rain or snow
fall in early Mars history. Subsurface water flow and
groundwater sapping may play important subsidiary roles
in some networks, but precipitation was probably the root
cause of the incision in almost all cases.* [73]
Along crater and canyon walls, there are also thousands
of features that appear similar to terrestrial gullies. The
gullies tend to be in the highlands of the southern hemisphere and to face the Equator; all are poleward of 30° latitude. A number of authors have suggested that their formation process involves liquid water, probably from melting ice,* [74]* [75] although others have argued for formation mechanisms involving carbon dioxide frost or the
movement of dry dust.* [76]* [77] No partially degraded
gullies have formed by weathering and no superimposed
impact craters have been observed, indicating that these
are young features, possibly even active today.* [75]
CHAPTER 2. MARS
Composition of“Yellowknife Bay”rocks – rock veins are higher
in calcium and sulfur than “Portage”soil – APXS results –
Curiosity rover (March 2013).
Francis McCubbin, a planetary scientist at the University
of New Mexico in Albuquerque looking at hydroxals in
crystalline minerals from Mars, states that the amount of
water in the upper mantle of Mars is equal to or greater
than that of Earth at 50–300 parts per million of water,
which is enough to cover the entire planet to a depth of
200–1,000 m (660–3,280 ft).* [85]
On March 18, 2013, NASA reported evidence from instruments on the Curiosity rover of mineral hydration,
likely hydrated calcium sulfate, in several rock samples
including the broken fragments of “Tintina”rock and
“Sutton Inlier”rock as well as in veins and nodules
in other rocks like “Knorr”rock and “Wernicke”
rock.* [86]* [87]* [88] Analysis using the rover's DAN instrument provided evidence of subsurface water, amounting to as much as 4% water content, down to a depth of
60 cm (24 in), in the rover's traverse from the Bradbury
Landing site to the Yellowknife Bay area in the Glenelg
terrain.* [86]
Other geological features, such as deltas and alluvial fans
preserved in craters, are further evidence for warmer,
wetter conditions at some interval or intervals in earlier
Mars history.* [78] Such conditions necessarily require
the widespread presence of crater lakes across a large proportion of the surface, for which there is also indepen- Some researchers think that much of the low northern
dent mineralogical, sedimentological and geomorpholog- plains of the planet were covered with an ocean hundreds
of meters deep, though this remains controversial.* [89]
ical evidence.* [79]
In March 2015, scientists stated that such ocean might
Further evidence that liquid water once existed on the sur- have been the size of Earth's Arctic Ocean. This findface of Mars comes from the detection of specific min- ing was derived from the ratio of water and deuterium
erals such as hematite and goethite, both of which some- in the modern Martian atmosphere compared to the ratimes form in the presence of water.* [80] Some of the tio found on Earth. Eight times as much deuterium was
evidence believed to indicate ancient water basins and found at Mars than exists on Earth, suggesting that anflows has been negated by higher resolution studies by the cient Mars had significantly higher levels of water. ReMars Reconnaissance Orbiter.* [81] In 2004, Opportunity sults from the Curiosity rover had previously found a high
detected the mineral jarosite. This forms only in the pres- ratio of deuterium in Gale Crater, though not significantly
ence of acidic water, which demonstrates that water once high enough to suggest the presence of an ocean. Other
existed on Mars.* [82] More recent evidence for liquid scientists caution that this new study has not been conwater comes from the finding of the mineral gypsum on firmed, and point out that Martian climate models have
the surface by NASA's Mars rover Opportunity in De- not yet shown that the planet was warm enough in the
cember 2011.* [83]* [84] Additionally, the study leader past to support bodies of liquid water.* [90]
2.1. PHYSICAL CHARACTERISTICS
Polar caps
Main article: Martian polar ice caps
North polar early summer ice cap (1999)
23
The seasonal frosting of some areas near the southern
ice cap results in the formation of transparent 1-metrethick slabs of dry ice above the ground. With the arrival of spring, sunlight warms the subsurface and pressure from subliming CO2 builds up under a slab, elevating and ultimately rupturing it. This leads to geyser-like
eruptions of CO2 gas mixed with dark basaltic sand or
dust. This process is rapid, observed happening in the
space of a few days, weeks or months, a rate of change
rather unusual in geology – especially for Mars. The gas
rushing underneath a slab to the site of a geyser carves
a spider-like pattern of radial channels under the ice, the
process being the inverted equivalent of an erosion network formed by water draining through a single plughole.* [101]* [102]* [103]* [104]
2.1.5 Geography and naming of surface
features
South polar midsummer ice cap (2000)
Main article: Geography of Mars
See also: Category:Surface features of Mars
Although better remembered for mapping the Moon,
Mars has two permanent polar ice caps. During a pole's
winter, it lies in continuous darkness, chilling the surface
and causing the deposition of 25–30% of the atmosphere
into slabs of CO2 ice (dry ice).* [91] When the poles are
again exposed to sunlight, the frozen CO2 sublimes, creating enormous winds that sweep off the poles as fast
as 400 km/h (250 mph). These seasonal actions transport large amounts of dust and water vapor, giving rise
to Earth-like frost and large cirrus clouds. Clouds of
water-ice were photographed by the Opportunity rover in
A MOLA-based topographic map showing highlands (red and
2004.* [92]
The polar caps at both poles consist primarily (70%) of
water ice. Frozen carbon dioxide accumulates as a comparatively thin layer about one metre thick on the north
cap in the northern winter only, whereas the south cap has
a permanent dry ice cover about eight metres thick.* [93]
This permanent dry ice cover at the south pole is peppered by flat floored, shallow, roughly circular pits, which
repeat imaging shows are expanding by meters per year;
this suggests that the permanent CO2 cover over the south
pole water ice is degrading over time.* [94] The northern polar cap has a diameter of about 1,000 km (620
mi) during the northern Mars summer,* [95] and contains
about 1.6 million cubic kilometres (380,000 cu mi) of ice,
which, if spread evenly on the cap, would be 2 km (1.2
mi) thick.* [96] (This compares to a volume of 2.85 million cubic kilometres (680,000 cu mi) for the Greenland
ice sheet.) The southern polar cap has a diameter of 350
km (220 mi) and a thickness of 3 km (1.9 mi).* [97] The
total volume of ice in the south polar cap plus the adjacent layered deposits has also been estimated at 1.6 million cubic km.* [98] Both polar caps show spiral troughs,
which recent analysis of SHARAD ice penetrating radar
has shown are a result of katabatic winds that spiral due
to the Coriolis Effect.* [99]* [100]
orange) dominating the southern hemisphere of Mars, lowlands
(blue) the northern. Volcanic plateaus delimit the northern plains
in some regions, whereas the highlands are punctuated by several
large impact basins.
Johann Heinrich Mädler and Wilhelm Beer were the first
“areographers”. They began by establishing that most of
Mars's surface features were permanent and by more precisely determining the planet's rotation period. In 1840,
Mädler combined ten years of observations and drew the
first map of Mars. Rather than giving names to the various markings, Beer and Mädler simply designated them
with letters; Meridian Bay (Sinus Meridiani) was thus
feature "a".* [105]
Today, features on Mars are named from a variety of
sources. Albedo features are named for classical mythology. Craters larger than 60 km are named for deceased
scientists and writers and others who have contributed to
the study of Mars. Craters smaller than 60 km are named
for towns and villages of the world with populations of
less than 100,000. Large valleys are named for the word
“Mars”or“star”in various languages; small valleys are
named for rivers.* [106]
Large albedo features retain many of the older names, but
24
are often updated to reflect new knowledge of the nature
of the features. For example, Nix Olympica (the snows
of Olympus) has become Olympus Mons (Mount Olympus).* [107] The surface of Mars as seen from Earth is
divided into two kinds of areas, with differing albedo.
The paler plains covered with dust and sand rich in reddish iron oxides were once thought of as Martian “continents”and given names like Arabia Terra (land of
Arabia) or Amazonis Planitia (Amazonian plain). The
dark features were thought to be seas, hence their names
Mare Erythraeum, Mare Sirenum and Aurorae Sinus.
The largest dark feature seen from Earth is Syrtis Major Planum.* [108] The permanent northern polar ice cap
is named Planum Boreum, whereas the southern cap is
called Planum Australe.
Mars's equator is defined by its rotation, but the location
of its Prime Meridian was specified, as was Earth's (at
Greenwich), by choice of an arbitrary point; Mädler and
Beer selected a line in 1830 for their first maps of Mars.
After the spacecraft Mariner 9 provided extensive imagery of Mars in 1972, a small crater (later called Airy-0),
located in the Sinus Meridiani “
( Middle Bay”or“Meridian Bay”), was chosen for the definition of 0.0° longitude
to coincide with the original selection.* [109]
Because Mars has no oceans and hence no “sea level”,
a zero-elevation surface also had to be selected as a reference level; this is also called the areoid* [110] of Mars,
analogous to the terrestrial geoid. Zero altitude was defined by the height at which there is 610.5 Pa (6.105
mbar) of atmospheric pressure.* [111] This pressure corresponds to the triple point of water, and it is about
0.6% of the sea level surface pressure on Earth (0.006
atm).* [112] In practice, today this surface is defined directly from satellite gravity measurements.
Map of quadrangles
The following imagemap of the planet Mars is divided
into the 30 quadrangles defined by the United States Geological Survey* [113]* [114] The quadrangles are numbered with the prefix “MC”for “Mars Chart.”* [115]
Click on the quadrangle and you will be taken to the corresponding article pages. North is at the top; 0°N 180°W
/ 0°N 180°W is at the far left on the equator. The map
images were taken by the Mars Global Surveyor.
0°N 180°W / 0°N 180°W
0°N 0°W / 0°N −0°E
90°N 0°W / 90°N −0°E
MC-01
Mare Boreum
MC-02
Diacria
MC-03
CHAPTER 2. MARS
Arcadia
MC-04
Mare Acidalium
MC-05
Ismenius Lacus
MC-06
Casius
MC-07
Cebrenia
MC-08
Amazonis
MC-09
Tharsis
MC-10
Lunae Palus
MC-11
Oxia Palus
MC-12
Arabia
MC-13
Syrtis Major
MC-14
Amenthes
MC-15
Elysium
MC-16
Memnonia
MC-17
Phoenicis
MC-18
Coprates
MC-19
Margaritifer
MC-20
2.1. PHYSICAL CHARACTERISTICS
Sabaeus
MC-21
Iapygia
MC-22
Tyrrhenum
MC-23
25
ern highlands, pitted and cratered by ancient impacts. Research in 2008 has presented evidence regarding a theory
proposed in 1980 postulating that, four billion years ago,
the northern hemisphere of Mars was struck by an object one-tenth to two-thirds the size of Earth's Moon. If
validated, this would make the northern hemisphere of
Mars the site of an impact crater 10,600 by 8,500 km
(6,600 by 5,300 mi) in size, or roughly the area of Europe, Asia, and Australia combined, surpassing the South
Pole–Aitken basin as the largest impact crater in the Solar
System.* [17]* [18]
Aeolis
MC-24
Phaethontis
MC-25
Thaumasia
MC-26
Argyre
MC-27
Noachis
MC-28
Hellas
MC-29
Eridania
MC-30
Mare Australe
Fresh asteroid impact on Mars 3°20′N 219°23′E / 3.34°N
219.38°E - before/March 27 & after/March 28, 2012
(MRO).* [116]
Mars is scarred by a number of impact craters: a total of
43,000 craters with a diameter of 5 km (3.1 mi) or greater
have been found.* [117] The largest confirmed of these is
the Hellas impact basin, a light albedo feature clearly visible from Earth.* [118] Due to the smaller mass of Mars,
the probability of an object colliding with the planet is
about half that of Earth. Mars is located closer to the
asteroid belt, so it has an increased chance of being struck
by materials from that source. Mars is also more likely to
be struck by short-period comets, i.e., those that lie within
the orbit of Jupiter.* [119] In spite of this, there are far
fewer craters on Mars compared with the Moon, because
the atmosphere of Mars provides protection against small
meteors. Some craters have a morphology that suggests
the ground became wet after the meteor impacted.* [120]
Volcanoes
Impact topography
Main article: Volcanism on Mars
The shield volcano Olympus Mons (Mount Olympus) is an
extinct volcano in the vast upland region Tharsis, which
contains several other large volcanoes. Olympus Mons is
roughly three times the height of Mount Everest, which in
comparison stands at just over 8.8 km (5.5 mi).* [121] It
is either the tallest or second tallest mountain in the Solar
System, depending on how it is measured, with various
sources giving figures ranging from about 21 to 27 km
(13 to 17 mi) high.* [122]* [123]
Tectonic sites
Bonneville crater and Spirit rover's lander
The large canyon, Valles Marineris (Latin for Mariner
The dichotomy of Martian topography is striking: north- Valleys, also known as Agathadaemon in the old canal
ern plains flattened by lava flows contrast with the south- maps), has a length of 4,000 km (2,500 mi) and a depth
26
CHAPTER 2. MARS
the“seven sisters”.* [127] Cave entrances measure from
100 to 252 m (328 to 827 ft) wide and they are believed
to be at least 73 to 96 m (240 to 315 ft) deep. Because
light does not reach the floor of most of the caves, it is
possible that they extend much deeper than these lower
estimates and widen below the surface. “Dena”is the
only exception; its floor is visible and was measured to be
130 m (430 ft) deep. The interiors of these caverns may
be protected from micrometeoroids, UV radiation, solar
flares and high energy particles that bombard the planet's
surface.* [128]
2.1.6 Atmosphere
Main article: Atmosphere of Mars
Viking orbiter view of Olympus Mons
MOLA colorized shaded-relief map of western hemisphere of
Mars showing Tharsis bulge (shades of red and brown). Tall
volcanoes appear white.
of up to 7 km (4.3 mi). The length of Valles Marineris
is equivalent to the length of Europe and extends across
one-fifth the circumference of Mars. By comparison, the
Grand Canyon on Earth is only 446 km (277 mi) long
and nearly 2 km (1.2 mi) deep. Valles Marineris was
formed due to the swelling of the Tharsis area which
caused the crust in the area of Valles Marineris to collapse. In 2012, it was proposed that Valles Marineris is
not just a graben, but also a plate boundary where 150
km (93 mi) of transverse motion has occurred, making
Mars a planet with possibly a two-plate tectonic arrangement.* [124]* [125]
Holes
Images from the Thermal Emission Imaging System
(THEMIS) aboard NASA's Mars Odyssey orbiter have
revealed seven possible cave entrances on the flanks of
the volcano Arsia Mons.* [126] The caves, named after
loved ones of their discoverers, are collectively known as
Escaping atmosphere on Mars (carbon, oxygen, and
hydrogen) by MAVEN in UV.* [129]
Mars lost its magnetosphere 4 billion years ago,* [130]
possibly because of numerous asteroid strikes,* [131]
so the solar wind interacts directly with the Martian
ionosphere, lowering the atmospheric density by stripping away atoms from the outer layer. Both Mars
Global Surveyor and Mars Express have detected ionised
atmospheric particles trailing off into space behind
Mars,* [130]* [132] and this atmospheric loss is being
studied by the MAVEN orbiter. Compared to Earth, the
atmosphere of Mars is quite rarefied. Atmospheric pressure on the surface today ranges from a low of 30 Pa
(0.030 kPa) on Olympus Mons to over 1,155 Pa (1.155
kPa) in Hellas Planitia, with a mean pressure at the surface level of 600 Pa (0.60 kPa).* [133] The highest atmospheric density on Mars is equal to that found 35 km (22
mi)* [134] above Earth's surface. The resulting mean surface pressure is only 0.6% of that of Earth (101.3 kPa).
The scale height of the atmosphere is about 10.8 km (6.7
mi),* [135] which is higher than Earth's (6 km (3.7 mi))
because the surface gravity of Mars is only about 38%
of Earth's, an effect offset by both the lower temperature
and 50% higher average molecular weight of the atmosphere of Mars.
2.1. PHYSICAL CHARACTERISTICS
27
Potential sources and sinks of methane (CH4 ) on Mars.
reach.* [145] The first measurements with the Tunable
Laser Spectrometer (TLS) indicated that there is less
than 5 ppb of methane at the landing site at the point of
the measurement.* [146]* [147]* [148]* [149] On SeptemThe tenuous atmosphere of Mars visible on the horizon.
ber 19, 2013, NASA scientists, from further measurements by Curiosity, reported no detection of atmospheric
methane with a measured value of 0.18±0.67 ppbv correThe atmosphere of Mars consists of about 96% carbon
sponding to an upper limit of only 1.3 ppbv (95% confidioxide, 1.93% argon and 1.89% nitrogen along with
dence limit) and, as a result, conclude that the probability
traces of oxygen and water.* [6]* [136] The atmosphere
of current methanogenic microbial activity on Mars is reis quite dusty, containing particulates about 1.5 µm in diduced.* [150]* [151]* [152]
ameter which give the Martian sky a tawny color when
seen from the surface.* [137]
Methane has been detected in the Martian atmosphere
with a mole fraction of about 30 ppb;* [14]* [138] it occurs in extended plumes, and the profiles imply that the
methane was released from discrete regions. In northern
midsummer, the principal plume contained 19,000 metric tons of methane, with an estimated source strength
of 0.6 kilograms per second.* [139]* [140] The profiles
suggest that there may be two local source regions, the
first centered near 30°N 260°W / 30°N 260°W and the
second near 0°N 310°W / 0°N 310°W.* [139] It is estimated that Mars must produce 270 tonnes per year of
methane.* [139]* [141]
The implied methane destruction lifetime may be as
long as about 4 Earth years and as short as about
0.6 Earth years.* [139]* [142] This rapid turnover would
indicate an active source of the gas on the planet.
Volcanic activity, cometary impacts, and the presence
of methanogenic microbial life forms are among possible sources. Methane could also be produced by a nonbiological process called serpentinization* [lower-alpha 2]
involving water, carbon dioxide, and the mineral olivine,
which is known to be common on Mars.* [143]
The Martian atmosphere as imaged by the Mars Orbiter Mission
The Curiosity rover, which landed on Mars in August Spacecraft
2012, is able to make measurements that distinguish
between different isotopologues of methane,* [144] but The Mars Orbiter Mission by India is currently searching
even if the mission is to determine that microscopic Mar- for methane in the armosphere,* [153] while the ExoMars
tian life is the source of the methane, the life forms Trace Gas Orbiter, planned to launch in 2016, would furlikely reside far below the surface, outside of the rover's ther study the methane as well as its decomposition prod-
28
CHAPTER 2. MARS
ucts, such as formaldehyde and methanol.* [154]
north, and near aphelion when it is winter in the southern hemisphere and summer in the north. As a result, the
seasons in the southern hemisphere are more extreme and
the seasons in the northern are milder than would otherwise be the case. The summer temperatures in the south
can reach up to 30 K (30 °C; 54 °F) warmer than the
equivalent summer temperatures in the north.* [161]
On 16 December 2014, NASA reported the Curiosity
rover detected a“tenfold spike”, likely localized, in the
amount of methane in the Martian atmosphere. Sample
measurements taken “a dozen times over 20 months”
showed increases in late 2013 and early 2014, averaging
“7 parts of methane per billion in the atmosphere.”Before and after that, readings averaged around one-tenth Mars also has the largest dust storms in the Solar System.
that level.* [155]* [156]
These can vary from a storm over a small area, to gigantic
Ammonia was also tentatively detected on Mars by the storms that cover the entire planet. They tend to occur
Mars Express satellite, but with its relatively short life- when Mars is closest to the Sun,*and have been shown to
time, it is not clear what produced it.* [157] Ammonia is increase the global temperature. [162]
not stable in the Martian atmosphere and breaks down
after a few hours. One possible source is volcanic activity.* [157]
2.2 Orbit and rotation
On 18 March 2015, NASA reported the detection of an
aurora that is not fully understood and an unexplained Main article: Orbit of Mars
Mars's average distance from the Sun is roughly 230 mildust cloud in the atmosphere of Mars.* [158]
2.1.7
Climate
Main article: Climate of Mars
Dust storm on Mars.
November 18, 2012
November 25, 2012
Opportunity and Curiosity rovers are noted.
Of all the planets in the Solar System, the seasons of Mars
are the most Earth-like, due to the similar tilts of the
two planets' rotational axes. The lengths of the Martian
seasons are about twice those of Earth's because Mars's
greater distance from the Sun leads to the Martian year
being about two Earth years long. Martian surface temperatures vary from lows of about −143 °C (−225 °F)
at the winter polar caps* [8] to highs of up to 35 °C (95
°F) in equatorial summer.* [9] The wide range in temperatures is due to the thin atmosphere which cannot store
much solar heat, the low atmospheric pressure, and the
low thermal inertia of Martian soil.* [159] The planet is
also 1.52 times as far from the Sun as Earth, resulting in
just 43% of the amount of sunlight.* [160]
Mars is about 230 million kilometres (143,000,000 mi) from the
Sun; its orbital period is 687 (Earth) days, depicted in red. Earth's
orbit is in blue.
lion kilometres (143,000,000 mi), and its orbital period
is 687 (Earth) days. The solar day (or sol) on Mars is only
slightly longer than an Earth day: 24 hours, 39 minutes,
and 35.244 seconds. A Martian year is equal to 1.8809
Earth years, or 1 year, 320 days, and 18.2 hours.* [6]
The axial tilt of Mars is 25.19 degrees relative to its
orbital plane, which is similar to the axial tilt of Earth.* [6]
As a result, Mars has seasons like Earth, though on Mars,
they are nearly twice as long because its orbital period is
that much longer. Currently, the orientation of the north
pole of Mars is close to the star Deneb.* [11] Mars passed
March 2010* [163] and its perihelion in
If Mars had an Earth-like orbit, its seasons would be sim- an aphelion in
*
[164] The next aphelion came in Februilar to Earth's because its axial tilt is similar to Earth's. March 2011.
*
ary
2012
[164]
and the next perihelion came in January
The comparatively large eccentricity of the Martian orbit
*
[164]
2013.
has a significant effect. Mars is near perihelion when it
is summer in the southern hemisphere and winter in the Mars has a relatively pronounced orbital eccentricity of
2.3. SEARCH FOR LIFE
29
about 0.09; of the seven other planets in the Solar System,
only Mercury has a larger orbital eccentricity. It is known
that in the past, Mars has had a much more circular orbit
than it does currently. At one point, 1.35 million Earth
years ago, Mars had an eccentricity of roughly 0.002,
much less than that of Earth today.* [165] Mars's cycle of
eccentricity is 96,000 Earth years compared to Earth's cycle of 100,000 years.* [166] Mars also has a much longer
cycle of eccentricity with a period of 2.2 million Earth
years, and this overshadows the 96,000-year cycle in the
eccentricity graphs. For the last 35,000 years, the orbit of
Mars has been getting slightly more eccentric because of
the gravitational effects of the other planets. The closest
distance between Earth and Mars will continue to mildly
decrease for the next 25,000 years.* [167]
2.3 Search for life
Main articles: Life on Mars and Viking lander biological
experiments
The current understanding of planetary habitability—the
Curiosity rover self-portrait at "Rocknest" (October 31, 2012),
with the rim of Gale Crater and the slopes of Aeolis Mons in the
distance.
Viking 1 Lander - sampling arm created deep trenches, scooping
up material for tests (Chryse Planitia).
ability of a world to develop and sustain life—favors planets that have liquid water on their surface. This most often
requires that the orbit of a planet lie within the habitable
zone, which for the Sun extends from just beyond Venus
to about the semi-major axis of Mars.* [168] During perihelion, Mars dips inside this region, but the planet's thin
(low-pressure) atmosphere prevents liquid water from existing over large regions for extended periods. The past
flow of liquid water demonstrates the planet's potential
for habitability. Some recent evidence has suggested that
any water on the Martian surface may have been too salty
and acidic to support regular terrestrial life.* [169]
The lack of a magnetosphere and extremely thin atmosphere of Mars are a challenge: the planet has little heat
transfer across its surface, poor insulation against bombardment of the solar wind and insufficient atmospheric
pressure to retain water in a liquid form (water instead
sublimes to a gaseous state). Mars is also nearly, or
perhaps totally, geologically dead; the end of volcanic
activity has apparently stopped the recycling of chemicals and minerals between the surface and interior of the
planet.* [170]
Evidence suggests that the planet was once significantly
more habitable than it is today, but whether living
organisms ever existed there remains unknown. The
Viking probes of the mid-1970s carried experiments designed to detect microorganisms in Martian soil at their
respective landing sites and had positive results, including a temporary increase of CO2 production on exposure
to water and nutrients. This sign of life was later disputed by some scientists, resulting in a continuing debate,
with NASA scientist Gilbert Levin asserting that Viking
may have found life. A re-analysis of the Viking data,
in light of modern knowledge of extremophile forms of
life, has suggested that the Viking tests were not sophisticated enough to detect these forms of life. The tests
could even have killed a (hypothetical) life form.* [171]
Tests conducted by the Phoenix Mars lander have shown
that the soil has a alkaline pH and it contains magnesium,
sodium, potassium and chloride.* [172] The soil nutrients
may be able to support life, but life would still have to
be shielded from the intense ultraviolet light.* [173] A recent analysis of martian meteorite EETA79001 found 0.6
ppm ClO4 * −, 1.4 ppm ClO3 * −, and 16 ppm NO3 * −, most
likely of martian origin. The ClO3 * − suggests presence
of other highly oxidizing oxychlorines such as ClO2 * −
or ClO, produced both by UV oxidation of Cl and Xray radiolysis of ClO4 * −. Thus only highly refractory
and/or well-protected (sub-surface) organics or life forms
are likely to survive.* [174] In addition, recent analysis
30
CHAPTER 2. MARS
of the Phoenix WCL showed that the Ca(ClO4 )2 in the
Phoenix soil has not interacted with liquid water of any
form, perhaps for as long as 600 Myr. If it had, the
highly soluble Ca(ClO4 )2 in contact with liquid water
would have formed only CaSO4. This suggests a severely
arid environment, with minimal or no liquid water interaction.* [175]
At the Johnson Space Center lab, some fascinating shapes
have been found in the meteorite ALH84001, which is
thought to have originated from Mars. Some scientists
propose that these geometric shapes could be fossilized
microbes extant on Mars before the meteorite was blasted
into space by a meteor strike and sent on a 15 million-year
voyage to Earth. An exclusively inorganic origin for the
shapes has also been proposed.* [176]
Panorama of Gusev crater, where Spirit rover examined volcanic
basalts
6, 2012 UTC. It is larger and more advanced than the
Mars Exploration Rovers, with a movement rate up to
90 m (300 ft) per hour.* [183] Experiments include a
laser chemical sampler that can deduce the make-up of
rocks at a distance of 7 m (23 ft).* [184] On February 10
the Curiosity rover obtained the first deep rock samples
ever taken from another planetary body, using its onboard
drill.* [185]
Small quantities of methane and formaldehyde recently detected by Mars orbiters are both claimed to
be possible evidence for life, as these chemical compounds would quickly break down in the Martian atmosphere.* [177]* [178] Alternatively, these compounds may
instead be replenished by volcanic or other geological
means, such as serpentinization.* [143]
On September 24, 2014, Mars Orbiter Mission (MOM),
launched by the Indian Space Research Organisation,
reached Mars orbit. ISRO launched MOM on Novem2.4 Habitability
ber 5, 2013, with the aim of analyzing the Martian atmosphere and topography. The Mars Orbiter Mission used
The German Aerospace Center discovered that Earth a Hohmann transfer orbit to escape Earth's gravitational
lichens can survive in simulated Mars conditions, mak- influence and catapult into a nine-month-long voyage to
ing the presence of life more plausible according to Mars. The mission is the first successful Asian interplan*
researcher Tilman Spohn.* [179] The simulation based etary mission. [186]
temperatures, atmospheric pressure, minerals, and light Several plans for a human mission to Mars have been proon data from Mars probes.* [179] An instrument called posed throughout the 20th century and into the 21st cenREMS is designed to provide new clues about the sig- tury but no active plan has an arrival date sooner than
nature of the Martian general circulation, microscale 2025.
weather systems, local hydrological cycle, destructive potential of UV radiation, and subsurface habitability based
on ground-atmosphere interaction.* [180]* [181] It landed
on Mars as part of Curiosity (MSL) in August 2012.
2.6 Astronomy on Mars
Main article: Astronomy on Mars
With the existence of various orbiters, landers, and
rovers, it is now possible to do astronomy from Mars.
Main article: Exploration of Mars
Although Mars's moon Phobos appears about one third
In addition to observation from Earth, some of the lat- the angular diameter of the full moon as it appears from
est Mars information comes from seven active probes on Earth, Deimos appears more or less star-like and appears
or in orbit around Mars, including five orbiters and two only slightly brighter than Venus does from Earth.* [187]
rovers. This includes 2001 Mars Odyssey,* [182] Mars Ex- There are various phenomena, well-known on Earth,
press, Mars Reconnaissance Orbiter, MAVEN, Mars Or- that have been observed on Mars, such as meteors and
biter Mission, Opportunity, and Curiosity.
auroras.* [188] A transit of Earth as seen from Mars
2.5 Exploration missions
will occur on November 10, 2084.* [189] There are also
transits of Mercury and transits of Venus, and the moons
Phobos and Deimos are of sufficiently small angular
diameter that their partial “eclipses”of the Sun are
best considered transits (see Transit of Deimos from
*
*
The Mars Science Laboratory, named Curiosity, launched Mars). [190] [191]
on November 26, 2011, and reached Mars on August On October 19, 2014, Comet Siding Spring passed exDozens of unmanned spacecraft, including orbiters,
landers, and rovers, have been sent to Mars by the Soviet
Union, the United States, Europe, and India to study the
planet's surface, climate, and geology. The public can request images of Mars via the HiWish program.
2.7. VIEWING
31
POV: Mars
Phobos transits the Sun (Opportunity; March 10, 2004).
Comet Siding Spring to pass near Mars on October 19, 2014
(Hubble; March 11, 2014).
Close encounter of Comet Siding Spring with the planet
tremely close to Mars, so close that the coma may have
Mars
enveloped Mars.* [192]* [193]* [194]* [195]* [196]* [197]
(composite image; Hubble ST; October 19, 2014).
Comet Siding Spring Mars flyby on October 19, 2014
(artist's concepts)
2.7 Viewing
POV: Universe
POV: Comet
Because the orbit of Mars is eccentric, its apparent magnitude at opposition from the Sun can range from −3.0 to
−1.4. The minimum brightness is magnitude +1.6 when
the planet is in conjunction with the Sun.* [10] Mars usually appears distinctly yellow, orange, or red; the actual
color of Mars is closer to butterscotch, and the redness
seen is just dust in the planet's atmosphere. NASA's
Spirit rover has taken pictures of a greenish-brown, mudcolored landscape with blue-grey rocks and patches of
light red sand.* [198] When farthest away from Earth, it is
more than seven times as far from the latter as when it is
closest. When least favorably positioned, it can be lost in
32
CHAPTER 2. MARS
days.
Absolute, around the present time
Animation of the apparent retrograde motion of Mars in 2003 as
seen from Earth
the Sun's glare for months at a time. At its most favorable
times—at 15- or 17-year intervals, and always between
late July and late September—a lot of surface detail can
be seen with a telescope. Especially noticeable, even at
low magnification, are the polar ice caps.* [199]
As Mars approaches opposition, it begins a period of
retrograde motion, which means it will appear to move
backwards in a looping motion with respect to the background stars. The duration of this retrograde motion lasts
for about 72 days, and Mars reaches its peak luminosity
in the middle of this motion.* [200]
2.7.1
Closest approaches
Relative
The point at which Mars's geocentric longitude is 180°
different from the Sun's is known as opposition, which is
near the time of closest approach to Earth. The time of
opposition can occur as much as 8.5 days away from the
closest approach. The distance at close approach varies
between about 54* [201] and about 103 million km due
to the planets' elliptical orbits, which causes comparable
variation in angular size.* [202] The last Mars opposition
occurred on April 8, 2014 at a distance of about 93 million km.* [203] The next Mars opposition occurs on May
22, 2016 at a distance of 76 million km.* [203] The average time between the successive oppositions of Mars, its
synodic period, is 780 days but the number of days between the dates of successive oppositions can range from
764 to 812.* [204]
As Mars approaches opposition it begins a period of
retrograde motion, which makes it appear to move backwards in a looping motion relative to the background
stars. The duration of this retrograde motion is about 72
Mars oppositions from 2003–2018, viewed from above the ecliptic with Earth centered
Mars made its closest approach to Earth and maximum
apparent brightness in nearly 60,000 years, 55,758,006
km (0.37271925 AU; 34,646,419 mi), magnitude −2.88,
on August 27, 2003 at 9:51:13 UT. This occurred when
Mars was one day from opposition and about three days
from its perihelion, making it particularly easy to see from
Earth. The last time it came so close is estimated to have
been on September 12, 57 617 BC, the next time being in 2287.* [205] This record approach was only slightly
closer than other recent close approaches. For instance,
the minimum distance on August 22, 1924 was 0.37285
AU, and the minimum distance on August 24, 2208 will
be 0.37279 AU.* [166]
2.8 Historical observations
Main article: History of Mars observation
The history of observations of Mars is marked by the oppositions of Mars, when the planet is closest to Earth and
hence is most easily visible, which occur every couple of
years. Even more notable are the perihelic oppositions
of Mars, which occur every 15 or 17 years and are distinguished because Mars is close to perihelion, making it
even closer to Earth.
2.8. HISTORICAL OBSERVATIONS
2.8.1
33
Ancient and medieval observations
The existence of Mars as a wandering object in the night
sky was recorded by the ancient Egyptian astronomers
and by 1534 BCE they were familiar with the retrograde
motion of the planet.* [206] By the period of the NeoBabylonian Empire, the Babylonian astronomers were Mars sketched as observed by Lowell sometime before
making regular records of the positions of the planets and 1914. (South top)
systematic observations of their behavior. For Mars, they
knew that the planet made 37 synodic periods, or 42 circuits of the zodiac, every 79 years. They also invented
arithmetic methods for making minor corrections to the
predicted positions of the planets.* [207]* [208]
In the fourth century BCE, Aristotle noted that Mars
disappeared behind the Moon during an occultation, indicating the planet was farther away.* [209] Ptolemy, a
Greek living in Alexandria,* [210] attempted to address
the problem of the orbital motion of Mars. Ptolemy's
model and his collective work on astronomy was presented in the multi-volume collection Almagest, which
became the authoritative treatise on Western astronomy
for the next fourteen centuries.* [211] Literature from ancient China confirms that Mars was known by Chinese astronomers by no later than the fourth century BCE.* [212]
In the fifth century CE, the Indian astronomical text Surya
Siddhanta estimated the diameter of Mars.* [213] In the
East Asian cultures, Mars is traditionally referred to as the
“fire star”(火星), based on the Five elements.* [214]
Map of Mars from Hubble Space Telescope as seen near
the 1999 opposition. (North top)
Main article: Martian canal
By the 19th century, the resolution of telescopes reached
a level sufficient for surface features to be identified. A
perihelic opposition of Mars occurred on September 5,
1877. In that year, Italian astronomer Giovanni Schiaparelli used a 22 cm (8.7 in) telescope in Milan to help
produce the first detailed map of Mars. These maps notably contained features he called canali, which were later
shown to be an optical illusion. These canali were supposedly long, straight lines on the surface of Mars, to which
he gave names of famous rivers on Earth. His term, which
During the seventeenth century, Tycho Brahe measured means “channels”or “grooves”, was popularly misthe diurnal parallax of Mars that Johannes Kepler used translated in English as “canals”.* [220]* [221]
to make a preliminary calculation of the relative distance
to the planet.* [215] When the telescope became avail- Influenced by the observations, the orientalist Percival
able, the diurnal parallax of Mars was again measured in Lowell founded an observatory which had 30 and 45 cm
an effort to determine the Sun-Earth distance. This was (12 and 18 in) telescopes. The observatory was used
first performed by Giovanni Domenico Cassini in 1672. for the exploration of Mars during the last good opporThe early parallax measurements were hampered by the tunity in 1894 and the following less favorable opposiquality of the instruments.* [216] The only occultation of tions. He published several books on Mars and life on the
*
Mars by Venus observed was that of October 13, 1590, planet, which had a great influence on the public. [222]
*
The
canali
were
also
found
by
other
astronomers,
like
seen by Michael Maestlin at Heidelberg. [217] In 1610,
Henri
Joseph
Perrotin
and
Louis
Thollon
in
Nice,
using
Mars was viewed by Galileo Galilei, who was first to see
*
*
it via telescope.* [218] The first person to draw a map of one of the largest telescopes of that time. [223] [224]
Mars that displayed any terrain features was the Dutch The seasonal changes (consisting of the diminishing of
astronomer Christiaan Huygens.* [219]
the polar caps and the dark areas formed during Martian
summer) in combination with the canals lead to speculation about life on Mars, and it was a long-held belief that
Mars contained vast seas and vegetation. The telescope
never reached the resolution required to give proof to
2.8.2 Martian “canals”
any speculations. As bigger telescopes were used, fewer
long, straight canali were observed. During an observation in 1909 by Flammarion with an 84 cm (33 in)
telescope, irregular patterns were observed, but no canali
were seen.* [225]
Map of Mars by Giovanni Schiaparelli
Even in the 1960s articles were published on Martian biology, putting aside explanations other than life for the
seasonal changes on Mars. Detailed scenarios for the
metabolism and chemical cycles for a functional ecosys-
34
CHAPTER 2. MARS
tem have been published.* [226]
2.8.3
Spacecraft visitation
Main article: Exploration of Mars
Once spacecraft visited the planet during NASA's
Foothills of Aeolis Mons (“Mount Sharp”) (white-balanced image).
Mariner missions in the 1960s and 70s these concepts
were radically broken. In addition, the results of the
Viking life-detection experiments aided an intermission
in which the hypothesis of a hostile, dead planet was generally accepted.* [227]
Mariner 9 and Viking allowed better maps of Mars to be
made using the data from these missions, and another major leap forward was the Mars Global Surveyor mission,
launched in 1996 and operated until late 2006, that allowed complete, extremely detailed maps of the Martian
topography, magnetic field and surface minerals to be obtained.* [228] These maps are now available online; for
example, at Google Mars. Mars Reconnaissance Orbiter
and Mars Express continued exploring with new instruments, and supporting lander missions.
2.9 In culture
Percival Lowell's books on the subject put forward the
standard notion of a planet that was a drying, cooling,
dying world with ancient civilizations constructing irrigation works.* [230]
Many other observations and proclamations by notable
personalities added to what has been termed “Mars
Fever”.* [231] In 1899 while investigating atmospheric
radio noise using his receivers in his Colorado Springs
lab, inventor Nikola Tesla observed repetitive signals that
he later surmised might have been radio communications
coming from another planet, possibly Mars. In a 1901
interview Tesla said:
It was some time afterward when the
thought flashed upon my mind that the disturbances I had observed might be due to an intelligent control. Although I could not decipher their meaning, it was impossible for me
to think of them as having been entirely accidental. The feeling is constantly growing on me
that I had been the first to hear the greeting of
one planet to another.* [232]
Main articles: Mars in culture and Mars in fiction
Mars is named after the Roman god of war. In different cultures, Mars represents masculinity and youth. Its
symbol, a circle with an arrow pointing out to the upper Tesla's theories gained support from Lord Kelvin who,
right, is also used as a symbol for the male gender.
while visiting the United States in 1902, was reported
The many failures in Mars exploration probes resulted in a to have said that he thought Tesla had picked up Mar*
satirical counter-culture blaming the failures on an Earth- tian signals being sent to the United States. [233] Kelvin
Mars "Bermuda Triangle", a "Mars Curse", or a "Great “emphatically”denied this report shortly before departGalactic Ghoul" that feeds on Martian spacecraft.* [229] ing America:“What I really said was that the inhabitants
of Mars, if there are any, were doubtless able to see New
York, particularly the glare of the electricity.”* [234]
2.9.1
Intelligent “Martians”
In a New York Times article in 1901, Edward Charles
Pickering, director of the Harvard College Observatory,
Main article: Mars in fiction
said that they had received a telegram from Lowell Observatory in Arizona that seemed to confirm that Mars was
The fashionable idea that Mars was populated by trying to communicate with Earth.* [235]
intelligent Martians exploded in the late 19th century. Schiaparelli's“canali”observations combined with
Early in December 1900, we received from
2.9. IN CULTURE
An 1893 soap ad playing on the popular idea that Mars was
populated
Lowell Observatory in Arizona a telegram that
a shaft of light had been seen to project from
Mars (the Lowell observatory makes a specialty of Mars) lasting seventy minutes. I wired
these facts to Europe and sent out neostyle
copies through this country. The observer
there is a careful, reliable man and there is no
reason to doubt that the light existed. It was
given as from a well-known geographical point
on Mars. That was all. Now the story has gone
the world over. In Europe it is stated that I
have been in communication with Mars, and all
sorts of exaggerations have spring up. Whatever the light was, we have no means of knowing. Whether it had intelligence or not, no one
can say. It is absolutely inexplicable.* [235]
35
Martian tripod illustration from the 1906 French edition of The
War of the Worlds by H.G. Wells
The depiction of Mars in fiction has been stimulated by
its dramatic red color and by nineteenth century scientific
speculations that its surface conditions might support not
just life but intelligent life.* [237] Thus originated a large
number of science fiction scenarios, among which is H. G.
Wells' The War of the Worlds, published in 1898, in which
Martians seek to escape their dying planet by invading
Earth. A subsequent US radio adaptation of The War of
the Worlds on October 30, 1938, by Orson Welles was
presented as a live news broadcast and became notorious
for causing a public panic when many listeners mistook it
for the truth.* [238]
Influential works included Ray Bradbury's The Martian Chronicles, in which human explorers accidentally
destroy a Martian civilization, Edgar Rice Burroughs'
Barsoom series, C. S. Lewis' novel Out of the Silent Planet
Pickering later proposed creating a set of mirrors in
(1938),* [239] and a number of Robert A. Heinlein stories
Texas, intended to signal Martians.* [236]
before the mid-sixties.* [240]
In recent decades, the high-resolution mapping of the surAuthor Jonathan Swift made reference to the moons of
face of Mars, culminating in Mars Global Surveyor, reMars, about 150 years before their actual discovery by
vealed no artifacts of habitation by “intelligent”life,
Asaph Hall, detailing reasonably accurate descriptions of
but pseudoscientific speculation about intelligent life on
their orbits, in the 19th chapter of his novel Gulliver's
Mars continues from commentators such as Richard C.
Travels.* [241]
Hoagland. Reminiscent of the canali controversy, some
speculations are based on small scale features perceived A comic figure of an intelligent Martian, Marvin the Marin the spacecraft images, such as 'pyramids' and the 'Face tian, appeared on television in 1948 as a character in
the Looney Tunes animated cartoons of Warner Brothon Mars'. Planetary astronomer Carl Sagan wrote:
ers, and has continued as part of popular culture to the
present.* [242]
Mars has become a kind of mythic arena
onto which we have projected our Earthly
hopes and fears.* [221]
After the Mariner and Viking spacecraft had returned
pictures of Mars as it really is, an apparently lifeless
36
and canal-less world, these ideas about Mars had to be
abandoned, and a vogue for accurate, realist depictions
of human colonies on Mars developed, the best known
of which may be Kim Stanley Robinson's Mars trilogy.
Pseudo-scientific speculations about the Face on Mars
and other enigmatic landmarks spotted by space probes
have meant that ancient civilizations continue to be a popular theme in science fiction, especially in film.* [243]
The theme of a Martian colony that fights for independence from Earth is a major plot element in the novels
of Greg Bear as well as the movie Total Recall (based
on a short story by Philip K. Dick) and the television series Babylon 5. Some video games also use this element,
including Red Faction and the Zone of the Enders series.
Mars (and its moons) were also the setting for the popular
Doom video game franchise and the later Martian Gothic.
CHAPTER 2. MARS
ters Phobos (panic/fear) and Deimos (terror/dread), who,
in Greek mythology, accompanied their father Ares, god
of war, into battle. Mars was the Roman counterpart of
Ares.* [245]* [246] In modern Greek, though, the planet
retains its ancient name Ares (Aris: Άρης).* [247]
From the surface of Mars, the motions of Phobos and
Deimos appear different from that of the Moon. Phobos
rises in the west, sets in the east, and rises again in just 11
hours. Deimos, being only just outside synchronous orbit
– where the orbital period would match the planet's period of rotation – rises as expected in the east but slowly.
Despite the 30 hour orbit of Deimos, 2.7 days elapse between its rise and set for an equatorial observer, as it
slowly falls behind the rotation of Mars.* [248]
2.10 Moons
Main articles: Moons of Mars, Phobos (moon) and
Deimos (moon)
Orbits of Phobos and Deimos (to scale)
Because the orbit of Phobos is below synchronous altitude, the tidal forces from the planet Mars are gradually
lowering its orbit. In about 50 million years, it could eiEnhanced-color HiRISE image of Phobos, showing a ther crash into Mars's surface or break up into a ring strucseries of mostly parallel grooves and crater chains, with ture around the planet.* [248]
its crater Stickney at right
The origin of the two moons is not well understood. Their
low albedo and carbonaceous chondrite composition have
been regarded as similar to asteroids, supporting the capture theory. The unstable orbit of Phobos would seem to
point towards a relatively recent capture. But both have
circular orbits, near the equator, which is unusual for captured objects and the required capture dynamics are complex. Accretion early in the history of Mars is also plausible, but would not account for a composition resembling
asteroids rather than Mars itself, if that is confirmed.
Enhanced-color HiRISE image of Deimos (not to scale),
showing its smooth blanket of regolith.
Mars has two relatively small natural moons, Phobos
(about 22 km (14 mi) in diameter) and Deimos (about 12
km (7.5 mi) in diameter), which orbit close to the planet.
Asteroid capture is a long-favored theory, but their origin
remains uncertain.* [244] Both satellites were discovered
in 1877 by Asaph Hall; they are named after the charac-
A third possibility is the involvement of a third body
or some kind of impact disruption.* [249] More recent
lines of evidence for Phobos having a highly porous interior,* [250] and suggesting a composition containing
mainly phyllosilicates and other minerals known from
Mars,* [251] point toward an origin of Phobos from material ejected by an impact on Mars that reaccreted in Martian orbit,* [252] similar to the prevailing theory for the
origin of Earth's moon. Although the VNIR spectra of
the moons of Mars resemble those of outer-belt asteroids, the thermal infrared spectra of Phobos are reported
2.13. NOTES
to be inconsistent with chondrites of any class.* [251]
Mars may have additional moons smaller than 50 to 100
metres (160 to 330 ft) in diameter, and a dust ring is predicted between Phobos and Deimos.* [253]
2.11 Gallery
• Streaks - on slopes in Acheron Fossae.
37
2.13 Notes
[1] Best fit ellipsoid
[2] There are many serpentinization reactions. Olivine is a
solid solution between forsterite and fayalite whose general formula is (Fe,Mg)2 SiO4 . The reaction producing
methane from olivine can be written as: Forsterite + Fayalite + Water + Carbonic acid → Serpentine + Magnetite +
Methane , or (in balanced form): 18Mg2 SiO4 + 6Fe2 SiO4
+ 26H2 O + CO2 → 12Mg3 Si2 O5 (OH)4 + 4Fe3 O4 + CH4
• Avalanche - down 700 m slope (north pole).
• Nanedi Valles inner channel.
• Valles Marineris (2001 Mars Odyssey).
• Mars - cave entrances (possible).
• Mars - suspected lava-tube skylight.
• Mars - North Pole area.
2.12 See also
• C/2013 A1—a comet passing near Mars in 2014
• Colonization of Mars
• Composition of Mars
• Darian calendar—time-keeping system
• Geodynamics on Mars
• Geology of Mars
• Extraterrestrial life
• Exploration of Mars
• List of artificial objects on Mars
• List of chasmata on Mars
• List of craters on Mars
• List of mountains on Mars
• List of quadrangles on Mars
• List of rocks on Mars
• List of valles on Mars
• Seasonal flows on warm Martian slopes
• Terraforming of Mars
• 2007 WD5—asteroid near-encounter with Mars on
January 30, 2008
• Water on Mars
2.14 References
[1] Yeomans, Donald K. (July 13, 2006). “HORIZONS
Web-Interface for Mars (Major Body=499)". JPL Horizons On-Line Ephemeris System. Retrieved August 8,
2007.—Select “Ephemeris Type: Orbital Elements”,
“Time Span: 2000-01-01 12:00 to 2000-01-02”. (“Target Body: Mars”and“Center: Sun”should be defaulted
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[226] Salisbury, F. B. (1962). “Martian Biology”. Science [244] “Close Inspection for Phobos”. ESA website. Retrieved
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2.15 External links
[240] Buker, Derek M. (2002). The science fiction and fantasy
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and sorcerers. ALA readers' advisory series. ALA Editions. p. 26. ISBN 0-8389-0831-4.
• Mars Exploration Program
[241] Darling, David.“Swift, Jonathan and the moons of Mars”
. Retrieved March 1, 2007.
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April 16, 2001)—Comparisons of terrains between
Earth and Mars
[242] Rabkin, Eric S. (2005). Mars: a tour of the human imagination. Greenwood Publishing Group. pp. 141–142.
ISBN 0-275-98719-1.
[243] Miles, Kathy; Peters II, Charles F.“Unmasking the Face”
. StarrySkies.com. Retrieved March 1, 2007.
• Mars at DMOZ
• On Mars: Exploration of the Red Planet 1958–1978
from the NASA History Office.
• Be on Mars—Anaglyphs from the Mars Rovers (3D)
• Mars articles in Planetary Science Research Discoveries
46
• Geody Mars—World's search engine that supports
NASA World Wind, Celestia, and other applications
• Mars Society—The Mars Society, an international
organization dedicated to the study, exploration, and
settlement of Mars.
• New Papers about Martian Geomorphology
• How far is it to Mars?
Media
• Video – Mars (National Oceanic and Atmospheric
Administration).
• Video (04:32) – Evidence for “Vigorously”Flowing Water on Ancient Mars (September 2012). on
YouTube
• Panoramic View of Gale Crater on Mars (4 billion
pixels) (March, 2013).
• Panoramic Views of Mars (Curiosity rover 1 and
Curiosity rover 2).
• Computer Simulated Flight into Mariner Valley.
• 3D-Flight into Mariner Valley.
• Mars at the Wayback Machine (archived January 5,
2008) Astronomy Cast episode #52, includes full
transcript.
• 15 Amazing Pictures of the Red Planet – slideshow
at The Huffington Post.
• Storm Front.
• Buried basins.
• Dunes. source.
• Mars. source.
Cartographic resources
• Mars nomenclature and Mars map with feature
names from the USGS planetary nomenclature page
• PDS Map-a-planet
• Viking Photomap
• MOLA (topographic) map
• 3D maps of Mars in NASA World Wind
• Google Mars—Interactive image of Mars
• Mars - Geologic Map (USGS, 2014) (original / crop
/ full / video (00:56)).
CHAPTER 2. MARS
Chapter 3
Mercury
3.4 Transportation
Mercury or The Mercury may refer to:
• Mercury (automobile), a marque of automobile produced by the Ford Motor Company (1938–2011)
3.1 Common meanings
• Mercury (cyclecar), an American cyclecar from
1914
• Mercury (element), a metallic chemical element
• Mercury (train), a family of New York Central
streamliner passenger trains (1936–1958)
• Mercury (planet), the planet closest to the Sun
• Blackburn Mercury, British aircraft from 1911
• Mercury (mythology), a Roman god
• Bristol Mercury, a 9-cylinder aircraft engine
• Russian brig Mercury, Russian warship
3.2 Places
• Mercury, Shuttle America's callsign
• Mercury Marine, a major manufacturer of marine
engines, particularly outboard motors
• Mercury Bay, on the North Island of New Zealand
• Mercury Islands, a group of islands off the northeast
coast of New Zealand
3.5 In entertainment
• Mercury, Nevada, a closed city within the Nevada
Test Site, United States
3.5.1
• Mercury, Savoie, a commune in southeastern France
Music
• Mercury Records, a record label
• Freddie Mercury, the frontman for the rock group
Queen
3.3 In the military
• Daniela Mercury, Brazilian singer, songwriter and
record producer
• Operation Mercury, codename for the German invasion of Crete during World War II
• HMS Mercury, the name of several ships of the
Royal Navy
• USS Mercury, the name of several ships of the
United States Navy
• Boeing E-6 Mercury, an American airborne command post and communications relay introduced in
1989
• Miles Mercury, a British aircraft designed during the
Second World War
47
• Mercury (Longview album)
• Mercury (American Music Club album)
• Mercury (Madder Mortem album)
• “Mercury”(song), a 2008 song by Bloc Party
•“Mercury”, a song by Kathleen Edwards from Failer
•“Mercury”, a song by Counting Crows from
Recovering the Satellites
•“Mercury, the Winged Messenger”, a movement in
Gustav Holst's The Planets
• Mercury Prize, an annual music prize awarded for
the best album from the United Kingdom
48
3.5.2
CHAPTER 3. MERCURY
Comics
3.7 Sports
• Mercury (Marvel Comics), a Marvel Comics character who can turn herself into a mercurial substance
• Edmonton Mercurys, a 1940s and 50s intermediate
ice hockey team from Canada
• Mercury (Amalgam Comics), a combination of the
characters Impulse and Quicksilver
• Phoenix Mercury, a Women's National Basketball
Association team from Arizona, United States
• Makkari (comics) or Mercury, an Eternal
• Mercury, a member of the Metal Men, a DC comics
team
• Mercury, a member of Cerebro's X-Men
3.5.3
Other
• Mercury (TV series), an Australian TV series
launched in 1996
• Mercury (novel), a 2005 novel by Ben Bova
• Sailor Mercury, a character in the Sailor Moon franchise
• Archer Maclean's Mercury, the first in a series of
games developed and/or published by Ignition Entertainment
3.6 Technology
• Toledo Mercurys, a defunct International Hockey
League franchise from Ohio, United States
3.8 Publications
• Mercury (magazine), an astronomy magazine
• Mercury (newspaper), a list
3.9 Radio stations
• 102.7 Mercury FM, a radio station in Surrey, United
Kingdom
• Mercury 96.6, a radio station in Hertfordshire,
United Kingdom
3.10 In business
• Project Mercury, the first human spaceflight program of the United States
• Mercury Communications, a British telecommunications firm set up in the 1980s
• Mercury (satellite), a series of three American satellites
• Mercury Insurance Group, an American automobile
and property insurance company
• Mercury (cipher machine), a British cipher machine
used from the 1950s
• The Mercury Mall, a shopping centre in Romford,
England
3.6.1
Computing
• The Mercury Award, an international airline award
for in-flight catering
• Mercury Interactive, software testing tools vendor
• Mercury (programming language), a functional/logical programming language based on
Prolog
3.11 Other uses
• Mercury (name), a given name and surname
• Mercury OS, a real-time operating system for embedded systems
• Mercury dime, a United States coin minted from
1916 through 1945
• Ferranti Mercury, an early 1950s commercial computer
• Mercury (plant), members of the plant genus Mercurialis
• Mercury Autocode, a programming language for the
Ferranti Mercury computer
• Mercury Boulevard, a road in Virginia, United
States
• Mercury Mail Transport System, a standardscompliant donationware mail server
• Mercury Fountain, a fountain in Tom Quad, Christ
Church College, Oxford, England
3.12. SEE ALSO
3.12 See also
• Mercur (disambiguation)
• Mercurius (disambiguation)
• Mercury 1 (disambiguation)
• Mercury 2 (disambiguation)
• Mercury 3 (disambiguation)
• Mercury 4 (disambiguation)
• Mercury House (disambiguation)
• Mercury program (disambiguation)
49
Chapter 4
Neptune
This article is about the planet. For other uses, see weather patterns. For example, at the time of the 1989
Neptune (disambiguation).
Voyager 2 flyby, the planet's southern hemisphere had
a Great Dark Spot comparable to the Great Red Spot
on Jupiter. These weather patterns are driven by the
Neptune is the eighth and farthest planet from the Sun in
the Solar System. It is the fourth-largest planet by diam- strongest sustained winds of any planet in the Solar System, with recorded wind speeds as high as 2,100 kilomeeter and the third-largest by mass. Among the gaseous
*
planets in the Solar System, Neptune is the most dense. tres per hour (1,300 mph). [15] Because of its great distance from the Sun, Neptune's outer atmosphere is one
Neptune is 17 times the mass of Earth and is slightly more
massive than its near-twin Uranus, which is 15 times the of the coldest places in the Solar System, with temperamass of Earth, and not as dense as Neptune.* [lower-alpha tures at its cloud tops approaching 55 K (−218 °C). Temcentre are approximately 5,400
3] Neptune orbits the Sun at an average distance of 30.1 peratures at the* planet's
*
K
(5,100
°C).
[16]
[17]
Neptune has a faint and fragastronomical units. Named after the Roman god of the
mented
ring
system
(labelled
“arcs”), which may have
sea, its astronomical symbol is ♆, a stylised version of the
been
detected
during
the
1960s
but was indisputably congod Neptune's trident.
firmed only in 1989 by Voyager 2.* [18]
Neptune was the first and only planet found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational 4.1 History
perturbation by an unknown planet. Neptune was subsequently observed on 23 September 1846* [1] by Johann
4.1.1 Discovery
Galle within a degree of the position predicted by Urbain
Le Verrier, and its largest moon, Triton, was discovered
shortly thereafter, though none of the planet's remaining Main article: Discovery of Neptune
13 moons were located telescopically until the 20th century. Neptune was visited by Voyager 2, when it flew by Some of the earliest recorded observations ever made
the planet on 25 August 1989.* [10]
through a telescope, Galileo's drawings on 28 December
Neptune is similar in composition to Uranus, and both 1612 and 27 January 1613, contain plotted points that
have compositions that differ from those of the larger gas match up with what is now known to be the position of
giants, Jupiter and Saturn. Neptune's atmosphere, like Neptune. On both occasions, Galileo seems to have misclose—
Jupiter's and Saturn's, is composed primarily of hydrogen taken Neptune for a fixed star when it appeared
*
in
conjunction—to
Jupiter
in
the
night
sky;
[19]
hence,
and helium, along with traces of hydrocarbons and possihe
is
not
credited
with
Neptune's
discovery.
At
his
first
bly nitrogen; it contains a higher proportion of“ices”such
observation
in
December
1612,
Neptune
was
almost
staas water, ammonia, and methane. Astronomers someretrograde
tionary
in
the
sky
because
it
had
just
turned
times categorise Uranus and Neptune as "ice giants" to
emphasise this distinction.* [11] The interior of Neptune, that day. This apparent backward motion is created when
like that of Uranus, is primarily composed of ices and Earth's orbit takes it past an outer planet. Because Neprock.* [12] Perhaps the core has a solid surface, but the tune was only beginning its yearly retrograde cycle, the
too slight to be detected with
temperature would be thousands of degrees and the at- motion of the planet was far
*
telescope.
[20]
In July 2009, University
Galileo's
small
*
mospheric pressure crushing. [13] Traces of methane in
of
Melbourne
physicist
David
Jamieson
announced new
the outermost regions in part account for the planet's blue
evidence
suggesting
that
Galileo
was
at
least
aware that
*
appearance. [14]
the star he had observed had moved relative to the fixed
In contrast to the hazy, relatively featureless atmosphere stars.* [21]
of Uranus, Neptune's atmosphere has active and visible
In 1821, Alexis Bouvard published astronomical ta50
4.1. HISTORY
bles of the orbit of Neptune's neighbour Uranus.* [22]
Subsequent observations revealed substantial deviations
from the tables, leading Bouvard to hypothesize that
an unknown body was perturbing the orbit through
gravitational interaction.* [23] In 1843, John Couch
Adams began work on the orbit of Uranus using the
data he had. Via Cambridge Observatory director James
Challis, he requested extra data from Sir George Airy,
the Astronomer Royal, who supplied it in February 1844.
Adams continued to work in 1845–46 and produced several different estimates of a new planet.* [24]* [25]
51
planet), failing to identify it owing to his casual approach
to the work.* [23]* [27]
In the wake of the discovery, there was much nationalistic rivalry between the French and the British over
who deserved credit for the discovery. Eventually an international consensus emerged that both Le Verrier and
Adams jointly deserved credit. Since 1966 Dennis Rawlins has questioned the credibility of Adams's claim to
co-discovery, and the issue was re-evaluated by historians with the return in 1998 of the “Neptune papers”
(historical documents) to the Royal Observatory, Greenwich.* [28] After reviewing the documents, they suggest
that “Adams does not deserve equal credit with Le Verrier for the discovery of Neptune. That credit belongs
only to the person who succeeded both in predicting the
planet's place and in convincing astronomers to search for
it.”* [29]
4.1.2 Naming
Shortly after its discovery, Neptune was referred to simply as “the planet exterior to Uranus”or as “Le Verrier's planet”. The first suggestion for a name came from
Galle, who proposed the name Janus. In England, Challis
put forward the name Oceanus.* [30]
Urbain Le Verrier
Claiming the right to name his discovery, Le Verrier
quickly proposed the name Neptune for this new planet,
though falsely stating that this had been officially approved by the French Bureau des Longitudes.* [31] In October, he sought to name the planet Le Verrier, after himself, and he had loyal support in this from the observatory
director, François Arago. This suggestion met with stiff
resistance outside France.* [32] French almanacs quickly
reintroduced the name Herschel for Uranus, after that
planet's discoverer Sir William Herschel, and Leverrier
for the new planet.* [33]
In 1845–46, Urbain Le Verrier, independently of Adams,
developed his own calculations but aroused no enthusiasm in his compatriots. In June 1846, upon seeing Le
Verrier's first published estimate of the planet's longitude
and its similarity to Adams's estimate, Airy persuaded Struve came out in favour of the name Neptune on 29 DeChallis to search for the planet. Challis vainly scoured cember 1846, to the Saint Petersburg Academy of Scithe sky throughout August and September.* [23]* [26]
ences.* [34] Soon Neptune became the internationally acMeanwhile, Le Verrier by letter urged Berlin Observatory cepted name. In Roman mythology, Neptune was the god
astronomer Johann Gottfried Galle to search with the ob- of the sea, identified with the Greek Poseidon. The deservatory's refractor. Heinrich d'Arrest, a student at the mand for a mythological name seemed to be in keeping
observatory, suggested to Galle that they could compare with the nomenclature of the other planets, all of which,
named for deities in Greek and
a recently drawn chart of the sky in the region of Le Ver- except for Earth, were
*
Roman
mythology.
[35]
rier's predicted location with the current sky to seek the
displacement characteristic of a planet, as opposed to a
fixed star. On the evening of 23 September 1846, the day
Galle received the letter, Neptune was discovered within
1° of where Le Verrier had predicted it to be, and about
12° from Adams' prediction. Challis later realised that
he had observed the planet twice in August (Neptune had
been observed on 8 and 12 August, but because Challis
lacked an up-to-date star map it was not recognised as a
Most languages today, even in countries that have no direct link to Greco-Roman culture, use some variant of the
name “Neptune”for the planet; in Chinese, Japanese
and Korean, the planet's name was translated as “sea
king star”(海王星), because Neptune was the god of the
sea.* [36] In modern Greek, though, the planet is called
Poseidon (Ποσειδώνας: Poseidonas), the Greek counterpart to Neptune.* [37]
52
4.1.3
CHAPTER 4. NEPTUNE
Status
concentrations of methane, ammonia and water are found
in the lower regions of the atmosphere.* [16]
From its discovery in 1846 until the subsequent discovery
of Pluto in 1930, Neptune was the farthest known planet.
Upon Pluto's discovery Neptune became the penultimate planet, save for a 20-year period between 1979
and 1999 when Pluto's elliptical orbit brought it closer to
the Sun than Neptune.* [38] The discovery of the Kuiper
belt in 1992 led many astronomers to debate whether
Pluto should be considered a planet in its own right or
part of the belt's larger structure.* [39]* [40] In 2006,
the International Astronomical Union defined the word
“planet”for the first time, reclassifying Pluto as a "dwarf
planet" and making Neptune once again the last planet in
the Solar System.* [41]
4.2 Composition and structure
A size comparison of Neptune and Earth
Neptune's mass of 1.0243×1026 kg,* [6] is intermediate
between Earth and the larger gas giants: it is 17 times
that of Earth but just 1/19th that of Jupiter.* [lower-alpha
4] Its surface gravity is surpassed only by Jupiter.* [42]
Neptune's equatorial radius of 24,764 km* [8] is nearly
four times that of Earth. Neptune and Uranus are often considered a subclass of gas giant termed "ice giants", due to their smaller size and higher concentrations
of volatiles relative to Jupiter and Saturn.* [43] In the
search for extrasolar planets Neptune has been used as
a metonym: discovered bodies of similar mass are often
referred to as“Neptunes”,* [44] just as astronomers refer
to various extra-solar bodies as “Jupiters”.
4.2.1
Internal structure
Neptune's internal structure resembles that of Uranus. Its
atmosphere forms about 5% to 10% of its mass and extends perhaps 10% to 20% of the way towards the core,
where it reaches pressures of about 10 GPa, or about
100,000 times that of Earth's atmosphere. Increasing
The internal structure of Neptune:
1. Upper atmosphere, top clouds
2. Atmosphere consisting of hydrogen, helium and methane gas
3. Mantle consisting of water, ammonia and methane ices
4. Core consisting of rock (silicates and nickel–iron)
The mantle is equivalent to 10 to 15 Earth masses and
is rich in water, ammonia and methane.* [1] As is customary in planetary science, this mixture is referred to as
icy even though it is a hot, dense fluid. This fluid, which
has a high electrical conductivity, is sometimes called
a water–ammonia ocean.* [45] The mantle may consist
of a layer of ionic water in which the water molecules
break down into a soup of hydrogen and oxygen ions, and
deeper down superionic water in which the oxygen crystallises but the hydrogen ions float around freely within
the oxygen lattice.* [46] At a depth of 7000 km, the conditions may be such that methane decomposes into diamond crystals that rain downwards like hailstones.* [47]
Very-high-pressure experiments at the Lawrence Livermore National Laboratory suggest that the base of the
mantle may comprise an ocean of liquid diamond, with
floating solid 'diamond-bergs'.* [48]* [49]
The core of Neptune is composed of iron, nickel and
silicates, with an interior model giving a mass about 1.2
times that of Earth.* [50] The pressure at the centre is 7
Mbar (700 GPa), about twice as high as that at the centre
of Earth, and the temperature may be 5,400 K.* [16]* [17]
4.2.2 Atmosphere
At high altitudes, Neptune's atmosphere is 80% hydrogen
and 19% helium.* [16] A trace amount of methane is
also present. Prominent absorption bands of methane
occur at wavelengths above 600 nm, in the red and infrared portion of the spectrum. As with Uranus, this absorption of red light by the atmospheric methane is part
of what gives Neptune its blue hue,* [51] although Neptune's vivid azure differs from Uranus's milder cyan. Because Neptune's atmospheric methane content is similar
4.2. COMPOSITION AND STRUCTURE
53
found at pressures of about 50 bars (5.0 MPa), where the
temperature reaches 273 K (0 °C). Underneath, clouds of
ammonia and hydrogen sulfide may be found.* [52]
High-altitude clouds on Neptune have been observed
casting shadows on the opaque cloud deck below. There
are also high-altitude cloud bands that wrap around the
planet at constant latitude. These circumferential bands
have widths of 50–150 km and lie about 50–110 km
above the cloud deck.* [53] These altitudes are in the layer
where weather occurs, the troposphere. Weather does not
occur in the higher stratosphere or thermosphere. Unlike
Uranus, Neptune's composition has a higher volume of
ocean, whereas Uranus has a smaller mantle.* [54]
Combined colour and near-infrared image of Neptune, showing bands of methane in its atmosphere, and four of its moons,
Proteus, Larissa, Galatea, and Despina.
Neptune's spectra suggest that its lower stratosphere
is hazy due to condensation of products of ultraviolet photolysis of methane, such as ethane and
acetylene.* [11]* [16] The stratosphere is also home
to that of Uranus, some unknown atmospheric constituent to trace amounts of carbon monoxide and hydrogen
cyanide.* [11]* [55] The stratosphere of Neptune is
is thought to contribute to Neptune's colour.* [14]
warmer than that of Uranus due to the elevated concenNeptune's atmosphere is subdivided into two main retration of hydrocarbons.* [11]
gions: the lower troposphere, where temperature decreases with altitude, and the stratosphere, where tem- For reasons that remain obscure, the planet's thermoperature increases with altitude. The boundary between sphere is at an anomalously high temperature of about
the two, the tropopause, occurs at a pressure of 0.1 bars 750 K.* [56]* [57] The planet is too far from the Sun for
(10 kPa).* [11] The stratosphere then gives way to the this heat to be generated by ultraviolet radiation. One
thermosphere at a pressure lower than 10* −5 to 10* −4 candidate for a heating mechanism is atmospheric intermicrobars (1 to 10 Pa).* [11] The thermosphere gradually action with ions in the planet's magnetic field. Other
candidates are gravity waves from the interior that distransitions to the exosphere.
sipate in the atmosphere. The thermosphere contains
traces of carbon dioxide and water, which may have been
deposited from external sources such as meteorites and
dust.* [52]* [55]
4.2.3 Magnetosphere
Neptune also resembles Uranus in its magnetosphere,
with a magnetic field strongly tilted relative to its
rotational axis at 47° and offset at least 0.55 radii, or
about 13500 km from the planet's physical centre. Before
Voyager 2's arrival at Neptune, it was hypothesised that
Uranus's tilted magnetosphere was the result of its sideways rotation. In comparing the magnetic fields of the
two planets, scientists now think the extreme orientation
may be characteristic of flows in the planets' interiors.
This field may be generated by convective fluid motions
Bands of high-altitude clouds cast shadows on Neptune's lower
in a thin spherical shell of electrically conducting liquids
cloud deck
(probably a combination of ammonia, methane and wa*
*
Models suggest that Neptune's troposphere is banded by ter) [52] resulting in a dynamo action. [58]
clouds of varying compositions depending on altitude. The dipole component of the magnetic field at the magThe upper-level clouds occur at pressures below one bar, netic equator of Neptune is about 14 microteslas (0.14
where the temperature is suitable for methane to con- G).* [59] The dipole magnetic moment of Neptune is
dense. For pressures between one and five bars (100 and about 2.2 × 1017 T·m3 (14 μT·RN 3 , where RN is the ra500 kPa), clouds of ammonia and hydrogen sulfide are dius of Neptune). Neptune's magnetic field has a complex
believed to form. Above a pressure of five bars, the clouds geometry that includes relatively large contributions from
may consist of ammonia, ammonium sulfide, hydrogen non-dipolar components, including a strong quadrupole
sulfide and water. Deeper clouds of water ice should be moment that may exceed the dipole moment in strength.
54
By contrast, Earth, Jupiter and Saturn have only relatively
small quadrupole moments, and their fields are less tilted
from the polar axis. The large quadrupole moment of
Neptune may be the result of offset from the planet's centre and geometrical constraints of the field's dynamo generator.* [60]* [61]
CHAPTER 4. NEPTUNE
ture,* [67] the cause of which is not understood but which
may be due to the gravitational interaction with small
moons in orbit near them.* [68]
The outermost ring, Adams, contains five prominent arcs
now named Courage, Liberté, Egalité 1, Egalité 2 and Fraternité (Courage, Liberty, Equality and Fraternity).* [69]
The existence of arcs was difficult to explain because the
laws of motion would predict that arcs would spread out
into a uniform ring over short timescales. Astronomers
now believe that the arcs are corralled into their current
form by the gravitational effects of Galatea, a moon just
inward from the ring.* [70]* [71]
Neptune's bow shock, where the magnetosphere begins
to slow the solar wind, occurs at a distance of 34.9 times
the radius of the planet. The magnetopause, where the
pressure of the magnetosphere counterbalances the solar
wind, lies at a distance of 23–26.5 times the radius of
Neptune. The tail of the magnetosphere extends out to
at least 72 times the radius of Neptune, and likely much Earth-based observations announced in 2005 appeared to
farther.* [60]
show that Neptune's rings are much more unstable than
previously thought. Images taken from the W. M. Keck
Observatory in 2002 and 2003 show considerable decay
4.3 Planetary rings
in the rings when compared to images by Voyager 2. In
particular, it seems that the Liberté arc might disappear
in as little as one century.* [72]
Main article: Rings of Neptune
Neptune has a planetary ring system, though one much
4.4 Climate
Neptune's rings, taken by Voyager 2
less substantial than that of Saturn. The rings may consist
of ice particles coated with silicates or carbon-based material, which most likely gives them a reddish hue.* [62]
The three main rings are the narrow Adams Ring, 63,000
km from the centre of Neptune, the Le Verrier Ring, at
53,000 km, and the broader, fainter Galle Ring, at 42,000
km. A faint outward extension to the Le Verrier Ring has
been named Lassell; it is bounded at its outer edge by the
Arago Ring at 57,000 km.* [63]
The first of these planetary rings was detected in 1968
by a team led by Edward Guinan.* [18]* [64] In the early
1980s, analysis of this data along with newer observations led to the hypothesis that this ring might be incomplete.* [65] Evidence that the rings might have gaps first
arose during a stellar occultation in 1984 when the rings
obscured a star on immersion but not on emersion.* [66]
Images by Voyager 2 in 1989 settled the issue by showing several faint rings. These rings have a clumpy struc-
The Great Dark Spot (top), Scooter (middle white cloud),* [73]
and the Small Dark Spot (bottom), with contrast exaggerated.
Neptune's weather is characterised by extremely dynamic
storm systems, with winds reaching speeds of almost
600 m/s (2,200 km/h; 1,300 mph) —nearly reaching
supersonic flow.* [15] More typically, by tracking the motion of persistent clouds, wind speeds have been shown to
vary from 20 m/s in the easterly direction to 325 m/s westward.* [74] At the cloud tops, the prevailing winds range
in speed from 400 m/s along the equator to 250 m/s at
the poles.* [52] Most of the winds on Neptune move in a
direction opposite the planet's rotation.* [75] The general
pattern of winds showed prograde rotation at high latitudes vs. retrograde rotation at lower latitudes. The difference in flow direction is believed to be a“skin effect”
and not due to any deeper atmospheric processes.* [11] At
4.4. CLIMATE
55
70° S latitude, a high-speed jet travels at a speed of 300 In 1989, the Great Dark Spot, an anti-cyclonic storm sysm/s.* [11]
tem spanning 13000×6600 km,* [76] was discovered by
Neptune differs from Uranus in its typical level of me- NASA's Voyager 2 spacecraft. The storm resembled the
teorological activity. Voyager 2 observed weather phe- Great Red Spot of Jupiter. Some five years later, on 2
nomena on Neptune during its 1989 fly-by,* [76] but no November 1994, the Hubble Space Telescope did not see
comparable phenomena on Uranus during its 1986 fly-by. the Great Dark Spot on the planet. Instead, a new storm
similar to the Great Dark Spot was found in the planet's
The abundance of methane, ethane and ethyne at Nep- northern hemisphere.* [80]
tune's equator is 10–100 times greater than at the poles.
This is interpreted as evidence for upwelling at the equa- The Scooter is another storm, a white cloud group farther south than the Great Dark Spot. Its nickname
tor and subsidence near the poles.* [11]
came when it was first detected in the months before
In 2007, it was discovered that the upper troposphere the 1989 Voyager 2 encounter it moved faster than the
of Neptune's south pole was about 10 K warmer than Great Dark Spot.* [75] Subsequent images revealed even
the rest of Neptune, which averages approximately 73 K faster clouds. The Small Dark Spot is a southern cyclonic
(−200 °C). The temperature differential is enough to let storm, the second-most-intense storm observed during
methane, which elsewhere is frozen in the troposphere, the 1989 encounter. It initially was completely dark, but
escape into the stratosphere near the pole.* [77] The rela- as Voyager 2 approached the planet, a bright core develtive “hot spot”is due to Neptune's axial tilt, which has oped and can be seen in most of the highest-resolution
exposed the south pole to the Sun for the last quarter of images.* [81]
Neptune's year, or roughly 40 Earth years. As Neptune
slowly moves towards the opposite side of the Sun, the Neptune's dark spots are thought to occur in the
at lower altitudes than the brighter cloud feasouth pole will be darkened and the north pole illumi- troposphere
tures,* [82] so they appear as holes in the upper cloud
nated, causing the methane release to shift to the north
decks. As they are stable features that can persist for sevpole.* [78]
eral months, they are thought to be vortex structures.* [53]
Because of seasonal changes, the cloud bands in the Often associated with dark spots are brighter, persissouthern hemisphere of Neptune have been observed to tent methane clouds that form around the tropopause
increase in size and albedo. This trend was first seen in layer.* [83] The persistence of companion clouds shows
1980 and is expected to last until about 2020. The long that some former dark spots may continue to exist as cyorbital period of Neptune results in seasons lasting forty clones even though they are no longer visible as a dark
years.* [79]
feature. Dark spots may dissipate when they migrate too
close to the equator or possibly through some other unknown mechanism.* [84]
4.4.1
Storms
4.4.2 Internal heating
The Great Dark Spot, as imaged by Voyager 2
Neptune's more varied weather when compared to
Uranus is believed to be due in part to its higher internal
heating. Although Neptune lies half again as far from
the Sun as Uranus, and receives only 40% its amount
of sunlight,* [11] the two planets' surface temperatures
are roughly equal.* [86] The upper regions of Neptune's
troposphere reach a low temperature of 51.8 K (−221.3
°C). At a depth where the atmospheric pressure equals
1 bar (100 kPa), the temperature is 72.00 K (−201.15
°C).* [87] Deeper inside the layers of gas, the temperature
rises steadily. As with Uranus, the source of this heating
is unknown, but the discrepancy is larger: Uranus only
radiates 1.1 times as much energy as it receives from the
Sun;* [88] whereas Neptune radiates about 2.61 times as
much energy as it receives from the Sun.* [89] Neptune is
the farthest planet from the Sun, yet its internal energy is
sufficient to drive the fastest planetary winds seen in the
Solar System. Depending on the thermal properties of its
interior, the heat left over from Neptune's formation may
be sufficient to explain its current heat flow, though it is
more difficult to simultaneously explain Uranus's lack of
internal heat while preserving the apparent similarity be-
56
CHAPTER 4. NEPTUNE
barycentric orbit since its discovery in 1846,* [92]* [93]
although it did not appear at its exact discovery position
in the sky, because Earth was in a different location in
its 365.26-day orbit. Because of the motion of the Sun
in relation to the barycentre of the Solar System, on 11
July Neptune was also not at its exact discovery position
in relation to the Sun; if the more common heliocentric
coordinate system is used, the discovery longitude was
reached on 12 July 2011.* [4]* [94]* [95]
The elliptical orbit of Neptune is inclined 1.77° compared
to that of Earth.
The axial tilt of Neptune is 28.32°,* [96] which is similar
to the tilts of Earth (23°) and Mars (25°). As a result, this
planet experiences similar seasonal changes. The long orbital period of Neptune means that the seasons last for
forty Earth years.* [79] Its sidereal rotation period (day)
is roughly 16.11 hours.* [4] Because its axial tilt is comparable to Earth's, the variation in the length of its day
over the course of its long year is not any more extreme.
Four images taken a few hours apart with the NASA/ESA Hubble
Space Telescope's Wide Field Camera 3* [85]
tween the two planets.* [90]
4.5 Orbit and rotation
Because Neptune is not a solid body, its atmosphere undergoes differential rotation. The wide equatorial zone
rotates with a period of about 18 hours, which is slower
than the 16.1-hour rotation of the planet's magnetic field.
By contrast, the reverse is true for the polar regions where
the rotation period is 12 hours. This differential rotation is the most pronounced of any planet in the Solar System,* [97] and it results in strong latitudinal wind
shear.* [53]
4.5.1 Orbital resonances
Main articles: Kuiper belt, resonant trans-Neptunian object and Neptune trojan
Neptune's orbit has a profound impact on the region diKuiper belt and orbital resonance
Pluto
1:2
Charon
2:3
Neptune
3:4
3:5 4:7
2:5
plutinos
cubewanos
twotinos
Neptune (red arc) completes one orbit around the Sun (center)
for every 164.79 orbits of Earth. The light blue object represents
Uranus.
The average distance between Neptune and the Sun is
4.50 billion km (about 30.1 AU), and it completes an orbit on average every 164.79 years, subject to a variability
of around ±0.1 years. The perihelion distance is 29.81
AU; the aphelion distance is 30.33 AU.* [91]
A diagram showing the major orbital resonances in the Kuiper
belt caused by Neptune: the highlighted regions are the 2:3 resonance (plutinos), the nonresonant“classical belt”(cubewanos),
and the 1:2 resonance (twotinos).
rectly beyond it, known as the Kuiper belt. The Kuiper
On 11 July 2011, Neptune completed its first full belt is a ring of small icy worlds, similar to the asteroid
4.7. MOONS
belt but far larger, extending from Neptune's orbit at 30
AU out to about 55 AU from the Sun.* [98] Much in the
same way that Jupiter's gravity dominates the asteroid
belt, shaping its structure, so Neptune's gravity dominates
the Kuiper belt. Over the age of the Solar System, certain
regions of the Kuiper belt became destabilised by Neptune's gravity, creating gaps in the Kuiper belt's structure.
The region between 40 and 42 AU is an example.* [99]
There do exist orbits within these empty regions where
objects can survive for the age of the Solar System. These
resonances occur when Neptune's orbital period is a precise fraction of that of the object, such as 1:2, or 3:4. If,
say, an object orbits the Sun once for every two Neptune orbits, it will only complete half an orbit by the
time Neptune returns to its original position. The most
heavily populated resonance in the Kuiper belt, with over
200 known objects,* [100] is the 2:3 resonance. Objects
in this resonance complete 2 orbits for every 3 of Neptune, and are known as plutinos because the largest of the
known Kuiper belt objects, Pluto, is among them.* [101]
Although Pluto crosses Neptune's orbit regularly, the 2:3
resonance ensures they can never collide.* [102] The 3:4,
3:5, 4:7 and 2:5 resonances are less populated.* [103]
57
suggest that the matter density in the outer regions of the
Solar System was too low to account for the formation of
such large bodies from the traditionally accepted method
of core accretion, and various hypotheses have been advanced to explain their creation. One is that the ice giants were not created by core accretion but from instabilities within the original protoplanetary disc and later
had their atmospheres blasted away by radiation from a
nearby massive OB star.* [43]
An alternative concept is that they formed closer to the
Sun, where the matter density was higher, and then subsequently migrated to their current orbits after the removal of the gaseous protoplanetary disc.* [107] This
hypothesis of migration after formation is favoured,
due to its ability to better explain the occupancy of
the populations of small objects observed in the transNeptunian region.* [108] The current most widely accepted* [109]* [110]* [111] explanation of the details of
this hypothesis is known as the Nice model, which explores the effect of a migrating Neptune and the other
giant planets on the structure of the Kuiper belt.
Neptune has a number of known trojan objects occupying
4.7 Moons
both the Sun–Neptune L4 and L5 Lagrangian points—
gravitationally stable regions leading and trailing Neptune
in its orbit, respectively.* [104] Neptune trojans can be Main article: Moons of Neptune
viewed as being in a 1:1 resonance with Neptune. Some For a timeline of discovery dates, see Timeline of discovNeptune trojans are remarkably stable in their orbits, and ery of Solar System planets and their moons.
are likely to have formed alongside Neptune rather than Neptune has 14 known moons.* [6]* [112] Triton is the
being captured. The first and so far only object identified as associated with Neptune's trailing L5 Lagrangian
point is 2008 LC18.* [105] Neptune also has a temporary
quasi-satellite, (309239) 2007 RW10.* [106] The object
has been a quasi-satellite of Neptune for about 12,500
years and it will remain in that dynamical state for another 12,500 years. It is likely a captured object.* [106]
4.6 Formation and migration
Main articles: Formation and evolution of the Solar System and Nice model
The formation of the ice giants, Neptune and Uranus,
A simulation showing the outer planets and Kuiper belt: a) before Jupiter and Saturn reached a 2:1 resonance; b) after inward
scattering of Kuiper belt objects following the orbital shift of Neptune; c) after ejection of scattered Kuiper belt bodies by Jupiter
has proven difficult to model precisely. Current models
Natural-colour view of Neptune with Proteus (top), Larissa
(lower right) and Despina (left), from the Hubble Space Telescope
58
largest Neptunian moon, comprising more than 99.5% of
the mass in orbit around Neptune,* [lower-alpha 5] and it
is the only one massive enough to be spheroidal. Triton
was discovered by William Lassell just 17 days after the
discovery of Neptune itself. Unlike all other large planetary moons in the Solar System, Triton has a retrograde
orbit, indicating that it was captured rather than forming
in place; it was probably once a dwarf planet in the Kuiper
belt.* [113] It is close enough to Neptune to be locked
into a synchronous rotation, and it is slowly spiralling inward because of tidal acceleration. It will eventually be
torn apart, in about 3.6 billion years, when it reaches the
Roche limit.* [114] In 1989, Triton was the coldest object
that had yet been measured in the Solar System,* [115]
with estimated temperatures of 38 K (−235 °C).* [116]
Neptune's second known satellite (by order of discovery),
the irregular moon Nereid, has one of the most eccentric
orbits of any satellite in the Solar System. The eccentricity of 0.7512 gives it an apoapsis that is seven times its
periapsis distance from Neptune.* [lower-alpha 6]
CHAPTER 4. NEPTUNE
Neptune was the Roman god of the sea, Neptune's moons
have been named after lesser sea gods.* [35]
4.8 Observation
Neptune is never visible to the naked eye, having a brightness between magnitudes +7.7 and +8.0,* [6]* [9] which
can be outshone by Jupiter's Galilean moons, the dwarf
planet Ceres and the asteroids 4 Vesta, 2 Pallas, 7 Iris,
3 Juno and 6 Hebe.* [120] A telescope or strong binoculars will resolve Neptune as a small blue disk, similar in
appearance to Uranus.* [121]
Because of the distance of Neptune from Earth, the
angular diameter of the planet only ranges from 2.2 to
2.4 arcseconds,* [6]* [9] the smallest of the Solar System planets. Its small apparent size has made it challenging to study visually. Most telescopic data was
fairly limited until the advent of Hubble Space Telescope and large ground-based telescopes with adaptive
optics.* [122]* [123]
From Earth, Neptune goes through apparent retrograde
motion every 367 days, resulting in a looping motion
against the background stars during each opposition.
These loops carried it close to the 1846 discovery coordinates in April and July 2010 and again in October and
November 2011.* [95]
Observation of Neptune in the radio-frequency band
shows that it is a source of both continuous emission and
irregular bursts. Both sources are believed to originate
from its rotating magnetic field.* [52] In the infrared part
of the spectrum, Neptune's storms appear bright against
the cooler background, allowing the size and shape of
these features to be readily tracked.* [124]
4.9 Exploration
Neptune's moon Proteus
From July to September 1989, Voyager 2 discovered
six new Neptunian moons.* [60] Of these, the irregularly shaped Proteus is notable for being as large as a
body of its density can be without being pulled into a
spherical shape by its own gravity.* [117] Although the
second-most-massive Neptunian moon, it is only 0.25%
the mass of Triton. Neptune's innermost four moons
—Naiad, Thalassa, Despina and Galatea —orbit close
enough to be within Neptune's rings. The next-farthest
out, Larissa, was originally discovered in 1981 when it
had occulted a star. This occultation had been attributed
to ring arcs, but when Voyager 2 observed Neptune in
1989, it was found to have caused it. Five new irregular moons discovered between 2002 and 2003 were
announced in 2004.* [118]* [119] A new moon and the
smallest yet, S/2004 N 1, was found in 2013. Because
Main article: Exploration of Neptune
Voyager 2 is the only spacecraft that has visited Neptune.
The spacecraft's closest approach to the planet occurred
on 25 August 1989. Because this was the last major planet
the spacecraft could visit, it was decided to make a close
flyby of the moon Triton, regardless of the consequences
to the trajectory, similarly to what was done for Voyager
1's encounter with Saturn and its moon Titan. The images
relayed back to Earth from Voyager 2 became the basis of
a 1989 PBS all-night program, Neptune All Night.* [125]
During the encounter, signals from the spacecraft required 246 minutes to reach Earth. Hence, for the most
part, the Voyager 2 mission relied on preloaded commands for the Neptune encounter. The spacecraft performed a near-encounter with the moon Nereid before it
came within 4400 km of Neptune's atmosphere on 25 August, then passed close to the planet's largest moon Triton
later the same day.* [126]
4.11. NOTES
59
4.11 Notes
[1] Orbital elements refer to the Neptune barycentre and
Solar System barycentre. These are the instantaneous
osculating values at the precise J2000 epoch. Barycentre
quantities are given because, in contrast to the planetary
centre, they do not experience appreciable changes on a
day-to-day basis from the motion of the moons.
[2] Refers to the level of 1 bar (100 kPa) atmospheric pressure
[3] Neptune is more dense and physically smaller than Uranus
because Neptune's greater mass gravitationally compresses the atmosphere more.
[4] The mass of Earth is 5.9736×1024 kg, giving a mass ratio
of:
MN eptune
MEarth
MU ranus
MEarth
In 2003, there was a proposal in NASA's “Vision
Missions Studies”for a "Neptune Orbiter with Probes"
mission that does Cassini-level science. The work is
being done in conjunction with JPL and the California
Institute of Technology.* [127] Another, more recent
proposal was for Argo, a flyby spacecraft that would visit
Jupiter, Saturn, Neptune, and a Kuiper belt object.* [128]
However, the focus would be on Neptune and its largest
moon Triton to help plug a predicted 50-year gap in
exploration of the system.* [128]* [128] New Horizons 2
might have also done a flyby.
4.10 See also
• Hot Neptune
• Neptune in astrology
• Neptune in fiction
5.97×10
The mass of Uranus is 8.6810×1025 kg, giving a mass ratio of:
A Voyager 2 mosaic of Triton
The spacecraft verified the existence of a magnetic field
surrounding the planet and discovered that the field was
offset from the centre and tilted in a manner similar to
the field around Uranus. The question of the planet's rotation period was settled using measurements of radio
emissions. Voyager 2 also showed that Neptune had a
surprisingly active weather system. Six new moons were
discovered, and the planet was shown to have more than
one ring.* [60]* [126]
26
= 1.02×1024 = 17.09
25
= 8.68×1024 = 14.54
5.97×10
The mass of Jupiter is 1.8986×1027 kg, giving a mass ratio
of:
MJupiter
MN eptune
27
= 1.90×1026 = 18.63
1.02×10
Mass values from Williams, David R. (29 November
2007). “Planetary Fact Sheet – Metric”. NASA. Retrieved 13 March 2008.
[5] Mass of Triton: 2.14×1022 kg. Combined mass of 12
other known moons of Neptune: 7.53×1019 kg, or 0.35%.
The mass of the rings is negligible.
[6]
ra
rp
2 −1=2/0.2488−1=7.039.
= 1−e
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[95] Anonymous (16 November 2007). “Horizons Output
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[115] Wilford, John N. (29 August 1989). “Triton May Be
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[103] John Davies (2001). Beyond Pluto: Exploring the outer
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[106] De La Fuente Marcos, C. & De La Fuente Mar2011-10-24.
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and Astrophysics Letters 545: L9. arXiv:1209.1577.
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Harold F. (2001). “The formation of Uranus and Neptune among Jupiter and Saturn”. The Astronomical [122] In 1977, for example, even the rotation period of Neptune
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nal, Part 2 – Letters to the Editor (University of Chicago
[108] Hansen, Kathryn (7 June 2005).“Orbital shuffle for early
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solar system”. Geotimes. Retrieved 26 August 2007.
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64
[123] Max, C.; MacIntosh, B.; Gibbard, S.; Roe, H. et
al. (1999). “Adaptive Optics Imaging of Neptune
and Titan with the W.M. Keck Telescope”. Bulletin of the American Astronomical Society 31: 1512.
Bibcode:1999BAAS...31.1512M.
[124] Gibbard, S. G.; Roe, H.; de Pater, I.; Macintosh, B. et al.
(1999).
“High-Resolution Infrared Imaging of Neptune from the Keck Telescope”
. Icarus 156 (1): 1–15. Bibcode:2002Icar..156....1G.
doi:10.1006/icar.2001.6766.
[125] Phillips, Cynthia (5 August 2003).“Fascination with Distant Worlds”. SETI Institute. Archived from the original
on 3 November 2007. Retrieved 3 October 2007.
[126] Burgess (1991):46–55.
[127] Spilker, T. R.; Ingersoll, A. P. (2004).“Outstanding Science in the Neptune System From an Aerocaptured Vision
Mission”. Bulletin of the American Astronomical Society
36: 1094. Bibcode:2004DPS....36.1412S.
[128] Argo - A Voyage Through the Outer Solar System
4.13 Bibliography
• Burgess, Eric (1991). Far Encounter: The Neptune
System. Columbia University Press. ISBN 978-0231-07412-4.
• Moore, Patrick (2000). The Data Book of Astronomy. CRC Press. ISBN 978-0-7503-0620-1.
4.14 Further reading
• Miner, Ellis D.; Wessen, Randii R. (2002). Neptune:
The Planet, Rings, and Satellites. Springer-Verlag.
ISBN 978-1-85233-216-7.
• Standage, Tom (2001). The Neptune File. Penguin.
ISBN 978-0-8027-1363-6.
4.15 External links
• NASA's Neptune fact sheet
• Neptune from Bill Arnett's nineplanets.org
• Neptune Astronomy Cast episode No. 63, includes
full transcript.
• Neptune Profile at NASA's Solar System Exploration site
• Planets – Neptune A children's guide to Neptune.
• Merrifield, Michael; Bauer, Amanda (2010).
“Neptune”. Sixty Symbols. Brady Haran for the
University of Nottingham.
• Neptune by amateur (The Planetary Society)
CHAPTER 4. NEPTUNE
Chapter 5
Saturn
This article is about the planet. For other uses, see
Saturn (disambiguation).
Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a
gas giant with an average radius about nine times that
of Earth.* [10]* [11] Although only one-eighth the average
density of Earth, with its larger volume Saturn is just over
95 times more massive.* [12]* [13]* [14] Saturn is named
after the Roman god of agriculture, its astronomical symbol (♄) represents the god's sickle.
Saturn's interior is probably composed of a core consisting of iron–nickel and rock (silicon and oxygen compounds), surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid
helium and a gaseous outer layer.* [15] Saturn has a pale
yellow hue due to ammonia crystals in its upper atmosphere. Electrical current within the metallic hydrogen layer is thought to give rise to Saturn's planetary
magnetic field, which is weaker than Earth's, but has a
magnetic moment 580 times that of Earth due to Saturn's
larger size. Saturn's magnetic field strength is around
one-twentieth the strength of Jupiter's.* [16] The outer
atmosphere is generally bland and lacking in contrast, although long-lived features can appear. Wind speeds on
Saturn can reach 1,800 km/h (500 m/s), faster than on
Jupiter, but not as fast as those on Neptune.* [17]
Composite image roughly comparing the sizes of Saturn and
Earth
surface, though it may have a solid core.* [20] Saturn's
rotation causes it to have the shape of an oblate spheroid;
that is, it is flattened at the poles and bulges at its equator. Its equatorial and polar radii differ by almost 10%:
60,268 km versus 54,364 km, respectively.* [4] Jupiter,
Uranus, and Neptune, the other giant planets in the Solar
System, are also oblate but to a lesser extent. Saturn is
the only planet of the Solar System that is less dense than
water—about 30% less.* [21] Although Saturn's core is
considerably denser than water, the average specific density of the planet is 0.69 g/cm3 due to the gaseous atmosphere. Jupiter has 318 times the Earth's mass,* [22]
while Saturn is 95 times the mass of the Earth,* [4] Together, Jupiter and Saturn hold 92% of the total planetary
mass in the Solar System.* [23]
Saturn has a prominent ring system that consists of nine
continuous main rings and three discontinuous arcs and
that is composed mostly of ice particles with a smaller
amount of rocky debris and dust. Sixty-two* [18] moons
are known to orbit Saturn, of which fifty-three are officially named. This does not include the hundreds of
moonlets comprising the rings. Titan, Saturn's largest and
the Solar System's second largest moon, is larger than the On 8 January 2015, NASA reported determining the cenplanet Mercury and is the only moon in the Solar System ter of the planet Saturn and its family of moons to within
4 km (2.5 mi).* [24]
to have a substantial atmosphere.* [19]
5.1 Physical characteristics
5.1.1 Internal structure
Despite consisting mostly of hydrogen and helium, most
Saturn is a gas giant because it is predominantly com- of Saturn's mass is not in the gas phase, because hydrogen
posed of hydrogen and helium ('gas'). It lacks a definite becomes a non-ideal liquid when the density is above 0.01
65
66
CHAPTER 5. SATURN
to the abundance of this element in the Sun.* [25] The
quantity of elements heavier than helium is not known
precisely, but the proportions are assumed to match the
primordial abundances from the formation of the Solar
System. The total mass of these heavier elements is esStandard planetary models suggest that the interior of Sat- timated to be 19–31 times the mass of the Earth, *with a
urn is similar to that of Jupiter, having a small rocky significant fraction located in Saturn's core region. [36]
core surrounded by hydrogen and helium with trace Trace amounts of ammonia, acetylene, ethane, propane,
amounts of various volatiles.* [25] This core is similar phosphine and methane have been detected in Satin composition to the Earth, but more dense. Exami- urn's atmosphere.* [37]* [38]* [39] The upper clouds are
nation of Saturn's gravitational moment, in combination composed of ammonia crystals, while the lower level
with physical models of the interior, allowed French as- clouds appear to consist of either ammonium hydrosultronomers Didier Saumon and Tristan Guillot to place fide (NH4 SH) or water.* [40] Ultraviolet radiation from
constraints on the mass of Saturn's core. In 2004, they the Sun causes methane photolysis in the upper atmoestimated that the core must be 9–22 times the mass of sphere, leading to a series of hydrocarbon chemical rethe Earth,* [26]* [27] which corresponds to a diameter of actions with the resulting products being carried downabout 25,000 km.* [28] This is surrounded by a thicker ward by eddies and diffusion. This photochemical cycle
liquid metallic hydrogen layer, followed by a liquid layer is modulated by Saturn's annual seasonal cycle.* [39]
of helium-saturated molecular hydrogen that gradually
transitions into gas with increasing altitude. The outermost layer spans 1,000 km and consists of a gaseous at- 5.2.1 Cloud layers
mosphere.* [29]* [30]* [31]
g/cm3 , which is reached at a radius containing 99.9%
of Saturn's mass. The temperature, pressure, and density inside Saturn all rise steadily toward the core, which,
in the deeper layers, cause hydrogen to transition into a
metal.* [23]
Saturn has a hot interior, reaching 11,700 °C at its core,
and it radiates 2.5 times more energy into space than it
receives from the Sun. Most of this extra energy is generated by the Kelvin–Helmholtz mechanism of slow gravitational compression, but this alone may not be sufficient to explain Saturn's heat production. An additional
mechanism may be generation of heat through the“raining out”of droplets of helium deep in Saturn's interior.
As the droplets descend through the lower-density hydrogen, the process releases heat by friction and leaves Saturn's outer layers depleted of helium.* [32]* [33] These
descending droplets may have accumulated into a helium
shell surrounding the core.* [25]
5.2 Atmosphere
A global storm girdles the planet in 2011. The head of the storm
(bright area) passes the tail circling around the left limb.
Saturn's atmosphere exhibits a banded pattern similar to
Jupiter's, but Saturn's bands are much fainter and are
much wider near the equator. The nomenclature used to
describe these bands is the same as on Jupiter. Saturn's
finer cloud patterns were not observed until the flybys of
the Voyager spacecraft during the 1980s. Since then,
Earth-based telescopy has improved to the point where
regular observations can be made.* [41]
The composition of the clouds varies with depth and increasing pressure. In the upper cloud layers, with the temperature in the range 100–160 K and pressures extending
The outer atmosphere of Saturn contains 96.3% molec- between 0.5–2 bar, the clouds consist of ammonia ice.
ular hydrogen and 3.25% helium by volume.* [35] The Water ice clouds begin at a level where the pressure is
proportion of helium is significantly deficient compared about 2.5 bar and extend down to 9.5 bar, where temperAuroral lights at Saturn’s north pole.* [34]
5.2. ATMOSPHERE
atures range from 185–270 K. Intermixed in this layer is a
band of ammonium hydrosulfide ice, lying in the pressure
range 3–6 bar with temperatures of 290–235 K. Finally,
the lower layers, where pressures are between 10–20 bar
and temperatures are 270–330 K, contains a region of
water droplets with ammonia in aqueous solution.* [42]
Saturn's usually bland atmosphere occasionally exhibits
long-lived ovals and other features common on Jupiter.
In 1990, the Hubble Space Telescope imaged an enormous white cloud near Saturn's equator that was not
present during the Voyager encounters and in 1994, another, smaller storm was observed. The 1990 storm
was an example of a Great White Spot, a unique but
short-lived phenomenon that occurs once every Saturnian year, roughly every 30 Earth years, around the time
of the northern hemisphere's summer solstice.* [43] Previous Great White Spots were observed in 1876, 1903,
1933 and 1960, with the 1933 storm being the most famous. If the periodicity is maintained, another storm will
occur in about 2020.* [44]
67
A persisting hexagonal wave pattern around the north polar vortex in the atmosphere at about 78°N was first noted
in the Voyager images.* [48]* [49]* [50]
The sides of the hexagon are each about 13,800 km
(8,600 mi) long, which is longer than the diameter of the
Earth.* [51] The entire structure rotates with a period of
10h 39m 24s (the same period as that of the planet's radio emissions) which is assumed to be equal to the period
of rotation of Saturn's interior.* [52] The hexagonal feature does not shift in longitude like the other clouds in the
visible atmosphere.* [53]
The pattern's origin is a matter of much speculation. Most
astronomers believe it was caused by some standing-wave
pattern in the atmosphere. Polygonal shapes have been
replicated in the laboratory through differential rotation
of fluids.* [54]* [55]
The winds on Saturn are the second fastest among the So- 5.2.3
lar System's planets, after Neptune's. Voyager data indicate peak easterly winds of 500 m/s (1800 km/h).* [45] In
images from the Cassini spacecraft during 2007, Saturn's
northern hemisphere displayed a bright blue hue, similar
to Uranus. The color was most likely caused by Rayleigh
scattering.* [46] Infrared imaging has shown that Saturn's
south pole has a warm polar vortex, the only known example of such a phenomenon in the Solar System.* [47]
Whereas temperatures on Saturn are normally −185 °C,
temperatures on the vortex often reach as high as −122
°C, believed to be the warmest spot on Saturn.* [47]
5.2.2
South pole vortex
North pole hexagonal cloud pattern
Saturn's south pole storm
Saturn – North polar hexagon and vortex as well as rings (2 April
2014)
Main article: Saturn's hexagon
HST imaging of the south polar region indicates the presence of a jet stream, but no strong polar vortex nor
any hexagonal standing wave.* [56] NASA reported in
November 2006 that Cassini had observed a "hurricanelike”storm locked to the south pole that had a clearly
defined eyewall.* [57]* [58] Eyewall clouds had not previously been seen on any planet other than Earth. For example, images from the Galileo spacecraft did not show
an eyewall in the Great Red Spot of Jupiter.* [59]
The south pole storm may have been present for billions
of years.* [60] This vortex is comparable to the size of
Earth, and it has winds of 550 km/h.* [60]
68
5.2.4
CHAPTER 5. SATURN
Other features
5.4 Orbit and rotation
Cassini has observed a series of cloud features nicknamed
“String of Pearls”found in northern latitudes. These features are cloud clearings that reside in deeper cloud layers.* [61]
5.3 Magnetosphere
Main article: Magnetosphere of Saturn
The average distance between Saturn and the Sun is over
Saturn has an intrinsic magnetic field that has a sim- 1.4 billion kilometres (9 AU). With an average orbital
speed of 9.69 km/s,* [4] it takes Saturn 10,759 Earth
days (or about 29 1 ⁄2 years),* [66] to finish one revolution
around the Sun.* [4] The elliptical orbit of Saturn is inclined 2.48° relative to the orbital plane of the Earth.* [4]
The perihelion and aphelion distances are, respectively,
9.022 and 10.053 au, on average.* [67] The visible features on Saturn rotate at different rates depending on latitude and multiple rotation periods have been assigned to
various regions (as in Jupiter's case).
System I has a period of 10 h 14 min 00 s (844.3°/d) and
encompasses the Equatorial Zone, the South Equatorial
Belt and the North Equatorial Belt.
All other Saturnian latitudes, excluding the north and
south polar regions, are indicated as System II and have
been assigned a rotation period of 10 h 38 min 25.4 s
(810.76°/d).
The polar regions are considered to have rotation rates
similar to System I.
HST UV image of Saturn taken near equinox showing both polar
aurorae
ple, symmetric shape – a magnetic dipole. Its strength
at the equator – 0.2 gauss (20 µT) – is approximately one
twentieth of that of the field around Jupiter and slightly
weaker than Earth's magnetic field.* [16] As a result Saturn's magnetosphere is much smaller than Jupiter's.* [62]
When Voyager 2 entered the magnetosphere, the solar
wind pressure was high and the magnetosphere extended only 19 Saturn radii, or 1.1 million km (712,000
mi),* [63] although it enlarged within several hours, and
remained so for about three days.* [64] Most probably,
the magnetic field is generated similarly to that of Jupiter
– by currents in the liquid metallic-hydrogen layer called
a metallic-hydrogen dynamo.* [62] This magnetosphere is
efficient at deflecting the solar wind particles from the
Sun. The moon Titan orbits within the outer part of
Saturn's magnetosphere and contributes plasma from the
ionized particles in Titan's outer atmosphere.* [16] Saturn's magnetosphere, like Earth's, produces aurorae.* [65]
System III refers to Saturn's internal rotation rate. Based
on radio emissions from the planet in the period of the
Voyager flybys, it has been assigned a rotation period
of 10 h 39 min 22.4 s (810.8°/d). Because it is close
to System II, it has largely superseded it.* [68] A precise
value for the rotation period of the interior remains elusive. While approaching Saturn in 2004, Cassini found
that the radio rotation period of Saturn had increased
appreciably, to approximately 10 h 45 m 45 s (± 36
s).* [69]* [70] In March 2007, it was found that the variation of radio emissions from the planet did not match
Saturn's rotation rate. This variance may be caused by
geyser activity on Saturn's moon Enceladus. The water
vapor emitted into Saturn's orbit by this activity becomes
charged and creates a drag upon Saturn's magnetic field,
slowing its rotation slightly relative to the rotation of the
planet.* [71]* [72]* [72]
The latest estimate of Saturn's rotation (as an indicated
rotation rate for Saturn as a whole) based on a compilation of various measurements from the Cassini, Voyager
and Pioneer probes was reported in September 2007 is 10
hours, 32 minutes, 35 seconds.* [73]
5.6. NATURAL SATELLITES
5.5 Planetary rings
69
Atlas cause weak, linear density waves in Saturn's rings
that have yielded more reliable calculations of their
masses.* [81]
Main article: Rings of Saturn
5.6 Natural satellites
Main article: Moons of Saturn
Saturn has at least 150 moons and moonlets, 53 of which
The rings of Saturn (imaged here by Cassini in 2007)
are the most massive and conspicuous in the Solar
System.* [30]
A montage of Saturn and its principal moons (Dione, Tethys,
False-color UV image of Saturn's outer B and A rings; Mimas, Enceladus, Rhea and Titan; Iapetus not shown). This
dirtier ringlets in the Cassini Division and Enke Gap famous image was created from photographs taken in November
show up red.
1980 by the Voyager 1 spacecraft.
Saturn is probably best known for the system of planetary
rings that makes it visually unique.* [30] The rings extend
from 6,630 km to 120,700 km above Saturn's equator, average approximately 20 meters in thickness and are composed of 93% water ice with traces of tholin impurities
and 7% amorphous carbon.* [74] The particles that make
up the rings range in size from specks of dust up to 10
m.* [75] While the other gas giants also have ring systems,
Saturn's is the largest and most visible.
have formal names.* [82]* [83] Titan, the largest, comprises more than 90% of the mass in orbit around Saturn,
including the rings.* [84] Saturn's second largest moon,
Rhea, may have a tenuous ring system of its own,* [85]
along with a tenuous atmosphere.* [86]* [87]* [88]* [89]
There are two main hypotheses regarding the origin of the
rings. One hypothesis is that the rings are remnants of a
destroyed moon of Saturn. The second hypothesis is that
the rings are left over from the original nebular material
from which Saturn formed. Some ice in the central rings
comes from the moon Enceladus's ice volcanoes.* [76] In
the past, astronomers believed the rings formed alongside
the planet when it formed billions of years ago.* [77] Instead, the age of these planetary rings is probably some
hundreds of millions of years.* [78]
Beyond the main rings at a distance of 12 million km from
the planet is the sparse Phoebe ring, which is tilted at an
angle of 27° to the other rings and, like Phoebe, orbits in
retrograde fashion.* [79]
Some of the moons of Saturn, including Pandora and Possible beginning of a new moon of Saturn (15 April 2013).
Prometheus, act as shepherd moons to confine the rings
and prevent them from spreading out.* [80] Pan and Many of the other moons are small: 34 are less than
70
10 km in diameter and another 14 less than 50 km but
larger than 10 km.* [90] Traditionally, most of Saturn's
moons have been named after Titans of Greek mythology. Titan is the only satellite in the Solar System with a
major atmosphere* [91]* [92] in which a complex organic
chemistry occurs. It is the only satellite with hydrocarbon
lakes.* [93]* [94]
CHAPTER 5. SATURN
suit. (In modern Greek, the planet retains its ancient
name Cronus—Κρόνος: Kronos.)* [109]
The Greek scientist Ptolemy based his calculations of Saturn's orbit on observations he made while the planet was
in opposition.* [110] In Hindu astrology, there are nine astrological objects, known as Navagrahas. Saturn, one of
them, is known as "Shani", judges everyone based on the
good and bad deeds performed in life.* [107]* [110] Ancient Chinese and Japanese culture designated the planet
Saturn as the “earth star”(土星). This was based on
Five Elements which were traditionally used to classify
natural elements.* [111]
On 6 June 2013, scientists at the IAA-CSIC reported
the detection of polycyclic aromatic hydrocarbons in
the upper atmosphere of Titan, a possible precursor for
life.* [95] On 23 June 2014, NASA claimed to have strong
evidence that nitrogen in the atmosphere of Titan came
from materials in the Oort cloud, associated with comets, In ancient Hebrew, Saturn is called 'Shabbathai'.* [112]
and not from the materials that formed Saturn in earlier Its angel is Cassiel. Its intelligence or beneficial spirit is
times.* [96]
Agiel (layga) and its spirit (darker aspect) is Zazel (lzaz).
Saturn's moon Enceladus has often been regarded as a po- In Ottoman Turkish, Urdu and Malay, its name is 'Zuhal',
tential base for microbial life.* [97]* [98]* [99]* [100] Ev- derived from Arabic ‫زحل‬.
idence of this possibility includes the satellite's salt-rich
particles having an “ocean-like”composition that indicates most of Enceladus's expelled ice comes from the 5.7.2 European observations (17th–19th
centuries)
evaporation of liquid salt water.* [101]* [102]* [103]
In April 2014, NASA scientists reported the possible beginning of a new moon, within the A Ring, of the planet
Saturn.* [104]
5.7 History of exploration
Main article: Exploration of Saturn
There have been three main phases in the observation and
exploration of Saturn. The first era was ancient observations (such as with the naked eye), before the invention of
the modern telescopes. Starting in the 17th century progressively more advanced telescopic observations from
Earth have been made. The other type is visitation by
spacecraft, either by orbiting or flyby. In the 21st century
observations continue from the Earth (or Earth-orbiting
observatories) and from the Cassini orbiter at Saturn.
Robert Hooke noted the shadows (a and b) cast by both the globe
and the rings on each other in this drawing of Saturn in 1666.
Saturn's rings require at least a 15-mm-diameter
telescope* [113] to resolve and thus were not known to
exist until Galileo first saw them in 1610.* [114]* [115]
He thought of them as two moons on Saturn's
sides.* [116]* [117] It was not until Christiaan Huygens
5.7.1 Ancient observations
used greater telescopic magnification that this notion
was refuted. Huygens discovered Saturn's moon Titan;
See also: Saturn (mythology)
Giovanni Domenico Cassini later discovered four other
moons: Iapetus, Rhea, Tethys and Dione. In 1675,
Saturn has been known since prehistoric times.* [105] In Cassini discovered the gap now known as the Cassini Diancient times, it was the most distant of the five known vision.* [118]
planets in the Solar System (excluding Earth) and thus
a major character in various mythologies. Babylonian No further discoveries of significance were made unastronomers systematically observed and recorded the til 1789 when William Herschel discovered two further
movements of Saturn.* [106] In ancient Roman mythol- moons, Mimas and Enceladus. The irregularly shaped
with Titan, was
ogy, the god Saturnus, from which the planet takes satellite Hyperion, which has a resonance
*
[119]
discovered
in
1848
by
a
British
team.
*
its name, was the god of agriculture. [107] The Romans considered Saturnus the equivalent of the Greek In 1899 William Henry Pickering discovered Phoebe,
god Cronus.* [107] The Greeks had made the outermost a highly irregular satellite that does not rotate synplanet sacred to Cronus,* [108] and the Romans followed chronously with Saturn as the larger moons do.* [119]
5.7. HISTORY OF EXPLORATION
71
Phoebe was the first such satellite found and it takes more the small Maxwell Gap (a gap within the C Ring) and
than a year to orbit Saturn in a retrograde orbit. During Keeler gap (a 42 km wide gap in the A Ring).
the early 20th century, research on Titan led to the confirmation in 1944 that it had a thick atmosphere – a feature
Cassini–Huygens spacecraft
unique among the Solar System's moons.* [120]
5.7.3
Modern NASA and ESA probes
Pioneer 11 flyby
On 1 July 2004, the Cassini–Huygens space probe performed the SOI (Saturn Orbit Insertion) maneuver and
entered orbit around Saturn. Before the SOI, Cassini had
already studied the system extensively. In June 2004,
it had conducted a close flyby of Phoebe, sending back
high-resolution images and data.
Pioneer 11 image of Saturn
Pioneer 11 carried out the first flyby of Saturn in September 1979, when it passed within 20,000 km of the planet's
cloud tops. Images were taken of the planet and a few of
its moons, although their resolution was too low to discern surface detail. The spacecraft also studied Saturn's
rings, revealing the thin F-ring and the fact that dark gaps
in the rings are bright when viewed at high phase angle
(towards the Sun), meaning that they contain fine lightscattering material. In addition, Pioneer 11 measured the
temperature of Titan.* [121]
Voyager flybys
Cassini 's Titan flyby radio-signal studies (artist's concept)
Cassini's flyby of Saturn's largest moon, Titan, has captured radar images of large lakes and their coastlines with
numerous islands and mountains. The orbiter completed
two Titan flybys before releasing the Huygens probe on
25 December 2004. Huygens descended onto the surface
of Titan on 14 January 2005, sending a flood of data during the atmospheric descent and after the landing.* [123]
Cassini has since conducted multiple flybys of Titan and
other icy satellites.
In November 1980, the Voyager 1 probe visited the Saturn system. It sent back the first high-resolution images
of the planet, its rings and satellites. Surface features of
various moons were seen for the first time. Voyager 1
performed a close flyby of Titan, increasing knowledge
of the atmosphere of the moon. It proved that Titan's atmosphere is impenetrable in visible wavelengths, therefore no surface details were seen. The flyby changed the
spacecraft's trajectory out from the plane of the Solar
System.* [122]
Almost a year later, in August 1981, Voyager 2 continued
the study of the Saturn system. More close-up images
of Saturn's moons were acquired, as well as evidence of
changes in the atmosphere and the rings. Unfortunately,
during the flyby, the probe's turnable camera platform
stuck for a couple of days and some planned imaging was
lost. Saturn's gravity was used to direct the spacecraft's
trajectory towards Uranus.* [122]
Photograph of Earth and the Moon by Cassini, visible in the
bottom-right.
Since early 2005, scientists have been tracking lightning
on Saturn. The power of the lightning is approximately
1,000 times that of lightning on Earth.* [124]
In 2006, NASA reported that Cassini had found evidence
of liquid water reservoirs that erupt in geysers on Saturn's
The probes discovered and confirmed several new satel- moon Enceladus. Images had shown jets of icy particles
lites orbiting near or within the planet's rings, as well as being emitted into orbit around Saturn from vents in the
72
CHAPTER 5. SATURN
At Enceladus's south pole geysers spray water from many locations along the tiger stripes.* [126]
Saturn's north polar vortex seen in (infrared) (animation)
moon's south polar region. According to Andrew Ingersoll, California Institute of Technology, “Other moons
in the Solar System have liquid-water oceans covered by
kilometers of icy crust. What's different here is that
pockets of liquid water may be no more than tens of meters below the surface.”* [125] Over 100 geysers have
been identified on Enceladus.* [126] In May 2011, NASA
scientists at an Enceladus Focus Group Conference reported that Enceladus“is emerging as the most habitable
spot beyond Earth in the Solar System for life as we know
it”.* [127]* [128]
Cassini photographs have led to other significant discoveries. They have revealed a previously undiscovered planetary ring, outside the brighter main rings of Saturn and
inside the G and E rings. The source of this ring is
believed to be the crashing of a meteoroid off two of
the moons of Saturn.* [129] In July 2006, Cassini images provided evidence of hydrocarbon lakes near Titan's
north pole, the presence of which were confirmed in January 2007. In March 2007, additional images near Titan's north pole revealed hydrocarbon seas, the largest
of which is almost the size of the Caspian Sea.* [130] In
October 2006, the probe detected an 8,000 km diameter cyclone-like storm with an eyewall at Saturn's south
pole.* [131]
From 2004 to 2 November 2009, the probe discovered
and confirmed 8 new satellites. Its primary mission ended
in 2008 when the spacecraft had completed 74 orbits
around the planet. The probe's mission was extended
to September 2010 and then extended again to 2017, to
study a full period of Saturn's seasons.* [132]
In April 2013 Cassini sent back images of a hurricane at
the planet's north pole 20 times larger than those found
on Earth, with winds faster than 530 km/h.* [133]
capture an image of the Earth and the Moon (and, as well,
Venus and Mars) as part of a natural light, multi-image
portrait of the entire Saturn system. It was the first time
NASA informed the people of Earth that a long-distance
photo was being taken in advance.* [134]
5.8 Observation
Amateur telescopic view
Saturn is the most distant of the five planets easily visible
to the naked eye, the other four being Mercury, Venus,
Mars and Jupiter. (Uranus and occasionally 4 Vesta are
visible to the naked eye in dark skies.) Saturn appears
to the naked eye in the night sky as a bright, yellowish
point of light with an apparent magnitude of usually between +1 and 0. It takes approximately 29.5 years for the
planet to complete an entire circuit of the ecliptic against
the background constellations of the zodiac. Most people will require an optical aid (very large binoculars or a
small telescope) that magnifies at least 30 times to achieve
an image of Saturn's rings, in which clear resolution is
present.* [30]* [113] Twice every Saturnian year (roughly
every 15 Earth years), the rings briefly disappear from
view, due to the way in which they are angled and because
they are so thin.* [135] Such a“disappearance”will next
occur in 2025, but Saturn will be too close to the Sun for
any ring-crossing observation to be possible.* [136]
On 19 July 2013, Cassini was pointed towards Earth to Saturn and its rings are best seen when the planet is at,
5.9. IN CULTURE
73
Horner explain the seasonal nature of Saturnian occultations:
This is the result of the fact that the moon’
s orbit around the Earth is tilted to the orbit of
the Earth around the Sun – and so most of the
time, the moon will pass above or below Saturn in the sky, and no occultation will occur. It
is only when Saturn lies near the point that the
moon’
s orbit crosses the“plane of the ecliptic”
that occultations can happen – and then they
occur every time the moon swings by, until Saturn moves away from the crossing point.* [138]
5.9 In culture
Simulated appearance of Saturn as seen from Earth
or near, opposition, the configuration of a planet when
it is at an elongation of 180°, and thus appears opposite
the Sun in the sky. A Saturnian opposition occurs every
year—approximately every 378 days—and results in the
planet appearing at its brightest. However, both the Earth
and Saturn orbit the Sun on eccentric orbits, which means
their distances from the Sun vary over time, and therefore so do their distances from each other, hence varying Saturn, from a 1550 edition of Guido Bonatti's Liber astronothe brightness of Saturn from one opposition to the other. miae
Also, Saturn appears brighter when the rings are angled
such that they are more visible. For example, during the Further information: Saturn in fiction
opposition of 17 December 2002, Saturn appeared at its
brightest due to a favorable orientation of its rings relative
to the Earth,* [137] even though Saturn was closer to the
• Saturn in astrology (
) is the ruling planet of
Earth and Sun in late 2003.* [137]
Capricorn and, traditionally, Aquarius.
• Saturn, the Bringer of Old Age is a movement in
Gustav Holst's The Planets.
• The Saturn family of rockets were developed by
a team of mostly German rocket scientists led by
Wernher von Braun to launch heavy payloads to
Earth orbit and beyond.* [139] Originally proposed
as a military satellite launcher, they were adopted as
the launch vehicles for the Apollo program.
Saturn eclipses the Sun, as seen from Cassini.
Also, from time to time Saturn is occulted by the Moon
(that is, the Moon covers up Saturn in the sky). As with
all the planets in the Solar System, occultations of Saturn occur in“seasons”. Saturnian occultations will take
place 12 or more times over a 12-month period, followed
by about a five-year period in which no such activity is
registered.* [138] Australian astronomy experts Hill and
• The day Saturday is named after the planet Saturn, which is derived from the Roman god of
agriculture, Saturn (linked to the Greek god
Cronus).* [140]* [141]
• In Saturn's Rings is an upcoming movie from director Stephen van Vuuren about Saturn. It features
more than a million photographs of the planet assembled with various techniques. The film is expected to be released in late 2014.
74
5.10 See also
• Dragon Storm (astronomy)
• Sixth planet (disambiguation)
• Space exploration
5.11 Notes
[1] Orbital elements refer to the barycenter of the Saturn system and are the instantaneous osculating values at the precise J2000 epoch. Barycenter quantities are given because, in contrast to the planetary centre, they do not experience appreciable changes on a day-to-day basis from
the motion of the moons.
[2] Refers to the level of 1 bar atmospheric pressure
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[114] Chan, Gary (2000). “Saturn: History Timeline”.
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Saturn moon”. BBC. Archived from the original on 5
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[139] Bilstein, Roger E. (1999). Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicle. DIANE
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“An overview of the descent and landing of
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5.13 Further reading
[126] Dyches, Preston et al. (28 July 2014).“Cassini Spacecraft
Reveals 101 Geysers and More on Icy Saturn Moon”.
NASA. Retrieved 29 July 2014.
[127] Lovett, Richard A. (31 May 2011).
“Enceladus
named sweetest spot for alien life”. Nature (Nature).
doi:10.1038/news.2011.337. Archived from the original
on 5 October 2011. Retrieved 3 June 2011.
• Lovett, L. et al. (2006). Saturn: A New View. New
York: Harry N. Abrams, Inc. ISBN 978-0-81093090-2.
• Karttunen, H. et al. (2007). Fundamental Astronomy (5th ed.). New York: Springer. ISBN 978-3540-34143-7.
5.14. EXTERNAL LINKS
5.14 External links
• Saturn profile at NASA's Solar System Exploration
site
• Saturn Fact Sheet, by NASA
• Gazeteer of Planetary Nomenclature – Saturn
(USGS)
• Cassini–Huygens mission to Saturn, by NASA
• Research News about Saturn
• General information about Saturn
• Studies on the Rings of Saturn
• Astronomy Cast: Saturn
• Saturn in Daytime (12 inch telescope)
• Saturn 'Rev 175' Raw Preview
• Haese, Paul. “Capturing Saturn”. Sixty Symbols.
Brady Haran for the University of Nottingham.
79
Chapter 6
Uranus
This article is about the planet. For other uses, see bit.* [18] Sir William Herschel announced its discovery
Uranus (disambiguation).
on March 13, 1781, expanding the known boundaries of
the Solar System for the first time in history. Uranus was
the first planet discovered with a telescope.
Uranus is the seventh planet from the Sun. It has the
third-largest planetary radius and fourth-largest planetary
mass in the Solar System. Uranus is similar in composition to Neptune, and both have different bulk chemical 6.1.1 Discovery
composition from that of the larger gas giants Jupiter and
Saturn. Therefore, astronomers increasingly place them Uranus had been observed on many occasions before its
in a separate category called "ice giants". Uranus's at- recognition as a planet, but it was generally mistaken for
mosphere, although similar to Jupiter's and Saturn's in its a star. Possibly the earliest known observation was by
primary composition of hydrogen and helium, contains Hipparchos, who in 128BC may have recorded the planet
more "ices", such as water, ammonia, and methane, along as a star for his star catalogue that was later incorpo*
with traces of other hydrocarbons.* [11] It is the coldest rated into Ptolemy's Almagest. [19] The earliest definite
planetary atmosphere in the Solar System, with a mini- sighting was in 1690 when John Flamsteed observed it at
mum temperature of 49 K (−224.2 °C), and has a com- least six times, cataloguing it as 34 Tauri. The French
plex, layered cloud structure, with water thought to make astronomer Pierre Lemonnier observed Uranus at least
*
up the lowest clouds, and methane the uppermost layer of twelve times between 1750 and 1769, [20] including on
clouds.* [11] The interior of Uranus is mainly composed four consecutive nights.
of ices and rock.* [10]
Sir William Herschel observed Uranus on March 13,
Uranus is the only planet whose name is derived from a 1781 from the garden of his house at 19 New King Street
figure from Greek mythology rather than Roman mythol- in Bath, Somerset, England (now the Herschel Museum
*
ogy, from the Latinized version of the Greek god of the of Astronomy), [21] and initially reported it (on April 26,
*
sky, Ouranos. Like the other giant planets, Uranus has a 1781) as a comet. [22] Herschel “engaged in a series of
*
ring system, a magnetosphere, and numerous moons. The observations on the parallax of the fixed stars”, [23] usUranian system has a unique configuration among those ing a telescope of his own design.
of the planets because its axis of rotation is tilted side- He recorded in his journal “In the quartile near ζ Tauri
ways, nearly into the plane of its revolution about the Sun. ... either [a] Nebulous star or perhaps a comet”.* [24] On
Its north and south poles therefore lie where most other March 17, he noted, “I looked for the Comet or Nebuplanets have their equators.* [16] In 1986, images from lous Star and found that it is a Comet, for it has changed
Voyager 2 showed Uranus as an almost featureless planet its place”.* [25] When he presented his discovery to the
in visible light, without the cloud bands or storms associ- Royal Society, he continued to assert that he had found a
ated with the other giant planets.* [16] Observations from comet, but also implicitly compared it to a planet:* [26]
Earth have shown seasonal change and increased weather
activity as Uranus approached its equinox in 2007. The
“The power I had on when I first saw the
wind speeds on Uranus can reach 250 metres per second
*
comet
was 227. From experience I know that
(900 km/h, 560 mph). [17]
the diameters of the fixed stars are not proportionally magnified with higher powers, as planets are; therefore I now put the powers at 460
6.1 History
and 932, and found that the diameter of the
comet increased in proportion to the power, as
Though Uranus is visible to the naked eye like the five
it ought to be, on the supposition of its not being
classical planets, it was never recognized as a planet by
a fixed star, while the diameters of the stars to
ancient observers because of its dimness and slow orwhich I compared it were not increased in the
80
6.1. HISTORY
same ratio. Moreover, the comet being magnified much beyond what its light would admit of,
appeared hazy and ill-defined with these great
powers, while the stars preserved that lustre and
distinctness which from many thousand observations I knew they would retain. The sequel
has shown that my surmises were well-founded,
this proving to be the Comet we have lately observed”.
81
star, which I had the honour of pointing out to them in
March 1781, is a Primary Planet of our Solar System.”
*
[31] In recognition of his achievement, King George III
gave Herschel an annual stipend of £200 on condition that
he move to Windsor so that the Royal Family could look
through his telescopes.* [32]
6.1.2 Naming
Maskelyne asked Herschel to“do the astronomical world
the faver [sic] to give a name to your planet, which is entirely your own, [and] which we are so much obliged to
you for the discovery of”.* [33] In response to Maskelyne's request, Herschel decided to name the object
Georgium Sidus (George's Star), or the“Georgian Planet”
in honour of his new patron, King George III.* [34] He
explained this decision in a letter to Joseph Banks:* [31]
In the fabulous ages of ancient times the
appellations of Mercury, Venus, Mars, Jupiter
and Saturn were given to the Planets, as being the names of their principal heroes and divinities. In the present more philosophical era
it would hardly be allowable to have recourse
to the same method and call it Juno, Pallas,
Apollo or Minerva, for a name to our new heavenly body. The first consideration of any particular event, or remarkable incident, seems to
be its chronology: if in any future age it should
be asked, when this last-found Planet was discovered? It would be a very satisfactory answer
to say, 'In the reign of King George the Third'.
Replica of the telescope used by Herschel to discover Uranus
(William Herschel Museum, Bath)
Herschel notified the Astronomer Royal, Nevil Maskelyne, of his discovery and received this flummoxed reply
from him on April 23: “I don't know what to call it. It is
as likely to be a regular planet moving in an orbit nearly
circular to the sun as a Comet moving in a very eccentric
ellipsis. I have not yet seen any coma or tail to it”.* [27]
Although Herschel continued to describe his new object
as a comet, other astronomers had already begun to suspect otherwise. Russian astronomer Anders Johan Lexell was the first to compute the orbit of the new object* [28] and its nearly circular orbit led him to a conclusion that it was a planet rather than a comet. Berlin
astronomer Johann Elert Bode described Herschel's discovery as “a moving star that can be deemed a hitherto
unknown planet-like object circulating beyond the orbit
of Saturn”.* [29] Bode concluded that its near-circular
orbit was more like a planet than a comet.* [30]
The object was soon universally accepted as a new planet.
By 1783, Herschel acknowledged this to Royal Society
president Joseph Banks:“By the observation of the most
eminent Astronomers in Europe it appears that the new William Herschel, discoverer of Uranus
82
CHAPTER 6. URANUS
Herschel's proposed name was not popular outside
Britain, and alternatives were soon proposed. Astronomer Jérôme Lalande proposed that it be named
Herschel in honour of its discoverer.* [35] Swedish astronomer Erik Prosperin proposed the name Neptune,
which was supported by other astronomers who liked the
idea to commemorate the victories of the British Royal
Naval fleet in the course of the American Revolutionary
War by calling the new planet even Neptune George III or
Neptune Great Britain.* [28] Bode opted for Uranus, the
Latinized version of the Greek god of the sky, Ouranos.
Bode argued that just as Saturn was the father of Jupiter,
the new planet should be named after the father of Saturn.* [32]* [36]* [37] In 1789, Bode's Royal Academy colleague Martin Klaproth named his newly discovered element uranium in support of Bode's choice.* [38] Ultimately, Bode's suggestion became the most widely used,
and became universal in 1850 when HM Nautical Almanac Office, the final holdout, switched from using Uranus revolves around the Sun once every 84 Earth years. Its
Georgium Sidus to Uranus.* [36]
average distance from the Sun is roughly 3 billion km (about 20
AU)
6.1.3
Name
Uranus is named after the ancient Greek deity of the sky
Uranus (Ancient Greek: Οὐρανός), the father of Cronus
(Saturn) and grandfather of Zeus (Jupiter), which in Latin
became "Ūranus”.* [1] It is the only planet whose name is
derived from a figure from Greek mythology rather than
Roman mythology. The adjective of Uranus is“Uranian”
.* [39] The pronunciation of the name Uranus preferred
among astronomers is /ˈjʊərənəs/,* [2] with stress on the
first syllable as in Latin Ūranus, in contrast to the colloquial /jʊˈreɪnəs/, with stress on the second syllable and
a long a, though both are considered acceptable.* [loweralpha 4]
Uranus has two astronomical symbols. The first to be
proposed, ♅,* [lower-alpha 5] was suggested by Lalande
in 1784. In a letter to Herschel, Lalande described it
as “un globe surmonté par la première lettre de votre
nom”(“a globe surmounted by the first letter of your
surname”).* [35] A later proposal, ,* [lower-alpha 6]
is a hybrid of the symbols for Mars and the Sun because Uranus was the Sky in Greek mythology, which was
thought to be dominated by the combined powers of the
Sun and Mars.* [41] In Chinese, Japanese, Korean, and
Vietnamese, its name is literally translated as the “sky
king star”(天王星).* [42]* [43]
6.2 Orbit and rotation
A 1998 false-colour near-infrared image of Uranus showing
cloud bands, rings, and moons obtained by the Hubble Space
Telescope's NICMOS camera.
on Uranus, at about 20 times the distance from the Sun
compared to Earth, it is about 1/400 the intensity of light
on Earth.* [45] Its orbital elements were first calculated
in 1783 by Pierre-Simon Laplace.* [46] With time, discrepancies began to appear between the predicted and
observed orbits, and in 1841, John Couch Adams first
proposed that the differences might be due to the gravitational tug of an unseen planet. In 1845, Urbain Le Verrier
began his own independent research into Uranus's orbit.
On September 23, 1846, Johann Gottfried Galle located
a new planet, later named Neptune, at nearly the position
predicted by Le Verrier.* [47]
Uranus orbits the Sun once every 84 Earth years. Its average distance from the Sun is roughly 3 billion km (about
20 AU). The variation of that distance is greater than that
of any other planet, at 1.8 AU.* [44] The intensity of sunlight reduces quadratically with distance, and therefore The rotational period of the interior of Uranus is 17
6.3. INTERNAL STRUCTURE
hours, 14 minutes, clockwise (retrograde). As on all giant
planets, its upper atmosphere experiences strong winds
in the direction of rotation. At some latitudes, such as
about 60 degrees south, visible features of the atmosphere
move much faster, making a full rotation in as little as 14
hours.* [48]
6.2.1
83
for Jupiter.* [12] At opposition, Uranus is visible to the
naked eye in dark skies, and becomes an easy target even
in urban conditions with binoculars.* [6] In larger amateur telescopes with an objective diameter of between 15
and 23 cm, Uranus appears as a pale cyan disk with distinct limb darkening. With a large telescope of 25 cm or
wider, cloud patterns, as well as some of the larger satellites, such as Titania and Oberon, may be visible.* [56]
Axial tilt
Uranus has an axial tilt of 97.77°, so its axis of rotation is 6.3 Internal structure
approximately parallel with the plane of the Solar System.
This gives it seasonal changes completely unlike those of
the other major planets. Other planets can be visualized
to rotate like tilted spinning tops on the plane of the Solar System, but Uranus rotates more like a tilted rolling
ball. Near the time of Uranian solstices, one pole faces
the Sun continuously and the other one faces away. Only a
narrow strip around the equator experiences a rapid day–
night cycle, but with the Sun low over the horizon as in
Earth's polar regions. At the other side of Uranus's orbit
the orientation of the poles towards the Sun is reversed.
Each pole gets around 42 years of continuous sunlight,
followed by 42 years of darkness.* [49] Near the time of
the equinoxes, the Sun faces the equator of Uranus giving a period of day–night cycles similar to those seen on
most of the other planets. Uranus reached its most recent
Size comparison of Earth and Uranus
equinox on December 7, 2007.* [50]* [51]
One result of this axis orientation is that, averaged over
the Uranian year, the polar regions of Uranus receive a
greater energy input from the Sun than its equatorial regions. Nevertheless, Uranus is hotter at its equator than
at its poles. The underlying mechanism that causes this
is unknown. The reason for Uranus's unusual axial tilt
is also not known with certainty, but the usual speculation is that during the formation of the Solar System, an
Earth-sized protoplanet collided with Uranus, causing the
skewed orientation.* [52] Uranus's south pole was pointed
almost directly at the Sun at the time of Voyager 2's flyby
in 1986. The labelling of this pole as “south”uses the
definition currently endorsed by the International Astronomical Union, namely that the north pole of a planet or
satellite is the pole that points above the invariable plane
of the Solar System, regardless of the direction the planet
is spinning.* [53]* [54] A different convention is sometimes used, in which a body's north and south poles are
defined according to the right-hand rule in relation to the
direction of rotation.* [55] In terms of this system it was
Uranus's north pole that was in sunlight in 1986.
6.2.2
Visibility
From 1995 to 2006, Uranus's apparent magnitude fluctuated between +5.6 and +5.9, placing it just within the
limit of naked eye visibility at +6.5.* [12] Its angular diameter is between 3.4 and 3.7 arcseconds, compared with
16 to 20 arcseconds for Saturn and 32 to 45 arcseconds
Diagram of the interior of Uranus
Uranus's mass is roughly 14.5 times that of Earth, making it the least massive of the giant planets. Its diameter is slightly larger than Neptune's at roughly four
times that of Earth. A resulting density of 1.27 g/cm3
makes Uranus the second least dense planet, after Saturn.* [8]* [9] This value indicates that it is made primarily of various ices, such as water, ammonia, and
methane.* [10] The total mass of ice in Uranus's interior
is not precisely known, because different figures emerge
depending on the model chosen; it must be between 9.3
and 13.5 Earth masses.* [10]* [57] Hydrogen and helium
constitute only a small part of the total, with between 0.5
and 1.5 Earth masses.* [10] The remainder of the non-ice
84
CHAPTER 6. URANUS
mass (0.5 to 3.7 Earth masses) is accounted for by rocky 6.3.1 Internal heat
material.* [10]
The standard model of Uranus's structure is that it con- Uranus's internal heat appears markedly lower than that
in astronomical terms, it has a
sists of three layers: a rocky (silicate/iron–nickel) core of the other giant*planets;
*
low
thermal
flux.
[17]
[64]
Why Uranus's internal temin the centre, an icy mantle in the middle and an outer
perature
is
so
low
is
still
not
understood.
Neptune, which
*
*
gaseous hydrogen/helium envelope. [10] [58] The core
is
Uranus's
near
twin
in
size
and
composition,
radiates
is relatively small, with a mass of only 0.55 Earth masses
2.61
times
as
much
energy
into
space
as
it
receives
from
and a radius less than 20% of Uranus's; the mantle
*
the
Sun,
[17]
but
Uranus
radiates
hardly
any
excess
heat
comprises its bulk, with around 13.4 Earth masses, and
at
all.
The
total
power
radiated
by
Uranus
in
the
far
inthe upper atmosphere is relatively insubstantial, weigh(i.e.
heat)
part
of
the
spectrum
is
1.06
±
0.08
times
frared
ing about 0.5 Earth masses and extending for the last
*
*
20% of Uranus's radius.* [10]* [58] Uranus's core density the solar energy absorbed in its atmosphere.2 [11] [65]
is around 9 g/cm3 , with a pressure in the center of Uranus's heat flux is only 0.042 ± 0.047 W/m , which is
the internal heat flux of Earth of about 0.075
8 million bars (800 GPa) and a temperature of about lower2than
*
W/m
.
[65]
The lowest temperature recorded in Uranus's
*
*
5000 K. [57] [58] The ice mantle is not in fact comtropopause
is
49 K (−224 °C), making Uranus the coldest
posed of ice in the conventional sense, but of a hot
planet
in
the
Solar
System.* [11]* [65]
and dense fluid consisting of water, ammonia and other
volatiles.* [10]* [58] This fluid, which has a high electri- One of the hypotheses for this discrepancy suggests that
cal conductivity, is sometimes called a water–ammonia when Uranus was hit by a supermassive impactor, which
ocean.* [59]
caused it to expel most of its primordial heat, it was left
*
According to research conducted at the University of with a depleted core temperature. [66] Another hypothCalifornia, Berkeley, the extreme pressure and temper- esis is that some form of barrier exists in Uranus's upper
ature deep within Uranus may break up the methane layers* that prevents the core's heat from reaching the surmolecules, with the carbon atoms condensing into crys- face. [10] For example, convection may take place in a
layers, which may inhibit
tals of diamond that rain down through the mantle like set of compositionally different
*
*
the
upward
heat
transport;
[11]
[65] perhaps double dif*
hailstones. [60] Very-high-pressure experiments at the
*
fusive
convection
is
a
limiting
factor.
[10]
Lawrence Livermore National Laboratory suggest that
the base of the mantle may comprise an ocean of liquid
diamond, with floating solid 'diamond-bergs'.* [61]* [62]
The bulk compositions of Uranus and Neptune are different from those of Jupiter and Saturn, with ice dominating
over gases, hence justifying their separate classification as
ice giants. There may be a layer of ionic water where the
water molecules break down into a soup of hydrogen and
oxygen ions, and deeper down superionic water in which
the oxygen crystallises but the hydrogen ions move freely
within the oxygen lattice.* [63]
6.4 Atmosphere
Main article: Atmosphere of Uranus
Although there is no well-defined solid surface within
Uranus's interior, the outermost part of Uranus's gaseous
envelope that is accessible to remote sensing is called
its atmosphere.* [11] Remote-sensing capability extends
down to roughly 300 km below the 1 bar (100 kPa) level,
with a corresponding pressure around 100 bar (10 MPa)
and temperature of 320 K.* [67] The tenuous corona of
the atmosphere extends over two planetary radii from the
nominal surface, which is defined to lie at a pressure of
1 bar.* [68] The Uranian atmosphere can be divided into
three layers: the troposphere, between altitudes of −300
and 50 km and pressures from 100 to 0.1 bar (10 MPa to
10 kPa); the stratosphere, spanning altitudes between 50
and 4000 km and pressures of between 0.1 and 10* −10
bar (10 kPa to 10 µPa); and the thermosphere/corona extending from 4,000 km to as high as 50,000 km from the
surface.* [11] There is no mesosphere.
Although the model considered above is reasonably standard, it is not unique; other models also satisfy observations. For instance, if substantial amounts of hydrogen
and rocky material are mixed in the ice mantle, the total mass of ices in the interior will be lower, and, correspondingly, the total mass of rocks and hydrogen will be
higher. Presently available data does not allow science
to determine which model is correct.* [57] The fluid interior structure of Uranus means that it has no solid surface.
The gaseous atmosphere gradually transitions into the internal liquid layers.* [10] For the sake of convenience, a
revolving oblate spheroid set at the point at which atmospheric pressure equals 1 bar (100 kPa) is conditionally
designated as a “surface”. It has equatorial and polar
radii of 25 559 ± 4 and 24 973 ± 20 km, respectively.* [8]
This surface is used throughout this article as a zero point 6.4.1 Composition
for altitudes.
The composition of Uranus's atmosphere is different
from its bulk, consisting mainly of molecular hydrogen
and helium.* [11] The helium molar fraction, i.e. the
6.4. ATMOSPHERE
number of helium atoms per molecule of gas, is 0.15 ±
0.03* [14] in the upper troposphere, which corresponds
to a mass fraction 0.26 ± 0.05.* [11]* [65] This value is
close to the protosolar helium mass fraction of 0.275 ±
0.01,* [69] indicating that helium has not settled in its
centre as it has in the gas giants.* [11] The third-mostabundant element in Uranus's atmosphere is methane
(CH4 ).* [11] Methane has prominent absorption bands
in the visible and near-infrared (IR), making Uranus
aquamarine or cyan in colour.* [11] Methane molecules
account for 2.3% of the atmosphere by molar fraction
below the methane cloud deck at the pressure level of 1.3
bar (130 kPa); this represents about 20 to 30 times the
carbon abundance found in the Sun.* [11]* [13]* [70] The
mixing ratio* [lower-alpha 7] is much lower in the upper
atmosphere due to its extremely low temperature, which
lowers the saturation level and causes excess methane to
freeze out.* [71] The abundances of less volatile compounds such as ammonia, water, and hydrogen sulfide
in the deep atmosphere are poorly known. They are
probably also higher than solar values.* [11]* [72] Along
with methane, trace amounts of various hydrocarbons are
found in the stratosphere of Uranus, which are thought
to be produced from methane by photolysis induced
by the solar ultraviolet (UV) radiation.* [73] They include ethane (C2 H6 ), acetylene (C2 H2 ), methylacetylene
(CH3 C2 H), and diacetylene (C2 HC2 H).* [71]* [74]* [75]
Spectroscopy has also uncovered traces of water vapor,
carbon monoxide and carbon dioxide in the upper atmosphere, which can only originate from an external source
such as infalling dust and comets.* [74]* [75]* [76]
6.4.2
Troposphere
The troposphere is the lowest and densest part of the atmosphere and is characterized by a decrease in temperature with altitude.* [11] The temperature falls from about
320 K at the base of the nominal troposphere at −300
km to 53 K at 50 km.* [67]* [70] The temperatures in the
coldest upper region of the troposphere (the tropopause)
actually vary in the range between 49 and 57 K depending
on planetary latitude.* [11]* [64] The tropopause region is
responsible for the vast majority of Uranus's thermal far
infrared emissions, thus determining its effective temperature of 59.1 ± 0.3 K.* [64]* [65]
The troposphere is believed to possess a highly complex cloud structure; water clouds are hypothesised to lie
in the pressure range of 50 to 100 bar (5 to 10 MPa),
ammonium hydrosulfide clouds in the range of 20 to 40
bar (2 to 4 MPa), ammonia or hydrogen sulfide clouds
at between 3 and 10 bar (0.3 to 1 MPa) and finally directly detected thin methane clouds at 1 to 2 bar (0.1 to
0.2 MPa).* [11]* [13]* [67]* [77] The troposphere is a dynamic part of the atmosphere, exhibiting strong winds,
bright clouds and seasonal changes.* [17]
85
6.4.3 Upper atmosphere
The middle layer of the Uranian atmosphere is the
stratosphere, where temperature generally increases with
altitude from 53 K in the tropopause to between 800
and 850 K at the base of the thermosphere.* [68] The
heating of the stratosphere is caused by absorption
of solar UV and IR radiation by methane and other
hydrocarbons,* [78] which form in this part of the atmosphere as a result of methane photolysis.* [73] Heat
is also conducted from the hot thermosphere.* [78] The
hydrocarbons occupy a relatively narrow layer at altitudes of between 100 and 300 km corresponding to a
pressure range of 10 to 0.1 mbar (1000 to 10 kPa) and
temperatures of between 75 and 170 K.* [71]* [74] The
most abundant hydrocarbons are methane, acetylene and
ethane with mixing ratios of around 10* −7 relative to hydrogen. The mixing ratio of carbon monoxide is similar at these altitudes.* [71]* [74]* [76] Heavier hydrocarbons and carbon dioxide have mixing ratios three orders
of magnitude lower.* [74] The abundance ratio of water is around 7×10* −9.* [75] Ethane and acetylene tend
to condense in the colder lower part of stratosphere and
tropopause (below 10 mBar level) forming haze layers,* [73] which may be partly responsible for the bland
appearance of Uranus. The concentration of hydrocarbons in the Uranian stratosphere above the haze is significantly lower than in the stratospheres of the other giant
planets.* [71]* [79]
The outermost layer of the Uranian atmosphere is the
thermosphere and corona, which has a uniform temperature around 800 to 850 K.* [11]* [79] The heat sources
necessary to sustain such a high level are not understood, as neither the solar UV nor the auroral activity can provide the necessary energy to maintain these
temperatures. The weak cooling efficiency due to the
lack of hydrocarbons in the stratosphere above 0.1 mBar
pressure level may contribute too.* [68]* [79] In addition
to molecular hydrogen, the thermosphere-corona contains many free hydrogen atoms. Their small mass and
high temperatures explain why the corona extends as
far as 50 000 km, or two Uranian radii, from its surface.* [68]* [79] This extended corona is a unique feature
of Uranus.* [79] Its effects include a drag on small particles orbiting Uranus, causing a general depletion of dust
in the Uranian rings.* [68] The Uranian thermosphere,
together with the upper part of the stratosphere, corresponds to the ionosphere of Uranus.* [70] Observations
show that the ionosphere occupies altitudes from 2 000
to 10 000 km.* [70] The Uranian ionosphere is denser
than that of either Saturn or Neptune, which may arise
from the low concentration of hydrocarbons in the stratosphere.* [79]* [80] The ionosphere is mainly sustained by
solar UV radiation and its density depends on the solar activity.* [81] Auroral activity is insignificant as compared
to Jupiter and Saturn.* [79]* [82]
• Uranus's atmosphere
86
CHAPTER 6. URANUS
• Temperature profile of the Uranian troposphere and is blue and the other one red.* [89]* [90] One hypothesis
lower stratosphere. Cloud and haze layers are also concerning the outer ring's blue colour is that it is comindicated.
posed of minute particles of water ice from the surface of
Mab that are small enough to scatter blue light.* [89]* [91]
• Zonal wind speeds on Uranus. Shaded areas show In contrast, Uranus's inner rings appear grey.* [89]
the southern collar and its future northern counterpart. The red curve is a symmetrical fit to the data.
• Uranus's rings
6.5 Planetary rings
Main article: Rings of Uranus
The rings are composed of extremely dark particles,
which vary in size from micrometres to a fraction of a
metre.* [16] Thirteen distinct rings are presently known,
the brightest being the ε ring. All except two rings of
Uranus are extremely narrow – they are usually a few kilometres wide. The rings are probably quite young; the dynamics considerations indicate that they did not form with
Uranus. The matter in the rings may once have been part
of a moon (or moons) that was shattered by high-speed
impacts. From numerous pieces of debris that formed as
a result of those impacts, only a few particles survived, in
stable zones corresponding to the locations of the present
rings.* [83]* [84]
William Herschel described a possible ring around
Uranus in 1789. This sighting is generally considered
doubtful, because the rings are quite faint, and in the two
following centuries none were noted by other observers.
Still, Herschel made an accurate description of the epsilon ring's size, its angle relative to Earth, its red colour,
and its apparent changes as Uranus travelled around the
Sun.* [85]* [86] The ring system was definitively discovered on March 10, 1977 by James L. Elliot, Edward W.
Dunham, and Jessica Mink using the Kuiper Airborne
Observatory. The discovery was serendipitous; they
planned to use the occultation of the star SAO 158687 by
Uranus to study its atmosphere. When their observations
were analysed, they found that the star had disappeared
briefly from view five times both before and after it disappeared behind Uranus. They concluded that there must
be a ring system around Uranus.* [87] Later they detected
four additional rings.* [87] The rings were directly imaged
when Voyager 2 passed Uranus in 1986.* [16] Voyager 2
also discovered two additional faint rings, bringing the
total number to eleven.* [16]
• Animation about the discovering occultation in
1977. (Click on it to start)
• Uranus has a complicated planetary ring system,
which was the second such system to be discovered
in the Solar System after Saturn's.* [1]
• Uranus's aurorae against its equatorial rings, imaged
by the Hubble telescope. Unlike the aurorae of
Earth and Jupiter, those of Uranus are not in line
with its poles, due to its lopsided magnetic field.
1. ^ Cite error: The named reference Esposito2002
was invoked but never defined (see the help page).
6.6 Magnetosphere
The magnetic field of Uranus as observed by Voyager 2 in 1986.
S and N are magnetic south and north poles.
Before the arrival of Voyager 2, no measurements of the
Uranian magnetosphere had been taken, so its nature remained a mystery. Before 1986, astronomers had expected the magnetic field of Uranus to be in line with
the solar wind, because it would then align with Uranus's
*
In December 2005, the Hubble Space Telescope detected poles that lie in the ecliptic. [92]
a pair of previously unknown rings. The largest is located Voyager's observations revealed that Uranus's magnetic
twice as far from Uranus as the previously known rings. field is peculiar, both because it does not originate from
These new rings are so far from Uranus that they are its geometric centre, and because it is tilted at 59° from
called the“outer”ring system. Hubble also spotted two the axis of rotation.* [92]* [93] In fact the magnetic dipole
small satellites, one of which, Mab, shares its orbit with is shifted from the Uranus's center towards the south rothe outermost newly discovered ring. The new rings bring tational pole by as much as one third of the planetary
the total number of Uranian rings to 13.* [88] In April radius.* [92] This unusual geometry results in a highly
2006, images of the new rings from the Keck Observa- asymmetric magnetosphere, where the magnetic field
tory yielded the colours of the outer rings: the outermost strength on the surface in the southern hemisphere can
6.7. CLIMATE
be as low as 0.1 gauss (10 µT), whereas in the northern
hemisphere it can be as high as 1.1 gauss (110 µT).* [92]
The average field at the surface is 0.23 gauss (23 µT).* [92]
In comparison, the magnetic field of Earth is roughly as
strong at either pole, and its“magnetic equator”is roughly
parallel with its geographical equator.* [93] The dipole
moment of Uranus is 50 times that of Earth.* [92]* [93]
Neptune has a similarly displaced and tilted magnetic
field, suggesting that this may be a common feature of ice
giants.* [93] One hypothesis is that, unlike the magnetic
fields of the terrestrial and gas giants, which are generated within their cores, the ice giants' magnetic fields are
generated by motion at relatively shallow depths, for instance, in the water–ammonia ocean.* [59]* [94] Another
possible explanation for the magnetosphere's alignment is
that there are oceans of liquid diamond in Uranus's interior that would deter the magnetic field.* [95]
87
Uranus's southern hemisphere in approximate natural colour
(left) and in shorter wavelengths (right), showing its faint cloud
bands and atmospheric “hood”as seen by Voyager 2
tire planet.* [16]* [99] One proposed explanation for this
dearth of features is that Uranus's internal heat appears
markedly lower than that of the other giant planets. The
Despite its curious alignment, in other respects the Uralowest temperature recorded in Uranus's tropopause is 49
nian magnetosphere is like those of other planets: it
K, making Uranus the coldest planet in the Solar System,
has a bow shock at about 23 Uranian radii ahead of it,
colder than Neptune.* [11]* [65]
a magnetopause at 18 Uranian radii, a fully developed
magnetotail, and radiation belts.* [92]* [93]* [96] Overall,
the structure of Uranus's magnetosphere is different from
Jupiter's and more similar to Saturn's.* [92]* [93] Uranus's 6.7.1 Banded structure, winds and clouds
magnetotail trails behind it into space for millions of kilometres and is twisted by its sideways rotation into a long In 1986, Voyager 2 found that the visible southern hemisphere of Uranus can be subdivided into two regions: a
corkscrew.* [92]* [97]
bright polar cap and dark equatorial bands.* [16] Their
Uranus's magnetosphere contains charged particles: boundary is located at about −45° of latitude. A narmainly protons and electrons, with a small amount of row band straddling the latitudinal range from −45 to
H2 * + ions.* [93]* [96] No heavier ions have been de- −50° is the brightest large feature on its visible surtected. Many of these particles probably derive from face.* [16]* [100] It is called a southern “collar”. The
the hot atmospheric corona.* [96] The ion and electron cap and collar are thought to be a dense region of methane
energies can be as high as 4 and 1.2 megaelectronvolts, clouds located within the pressure range of 1.3 to 2 bar
respectively.* [96] The density of low-energy (below 1 (see above).* [101] Besides the large-scale banded struckiloelectronvolt) ions in the inner magnetosphere is about ture, Voyager 2 observed ten small bright clouds, most
2 cm* −3.* [98] The particle population is strongly af- lying several degrees to the north from the collar.* [16]
fected by the Uranian moons, which sweep through the In all other respects Uranus looked like a dynamically
magnetosphere, leaving noticeable gaps.* [96] The par- dead planet in 1986. Voyager 2 arrived during the height
ticle flux is high enough to cause darkening or space of Uranus's southern summer and could not observe the
weathering of their surfaces on an astronomically rapid northern hemisphere. At the beginning of the 21st centimescale of 100,000 years.* [96] This may be the cause tury, when the northern polar region came into view, the
of the uniformly dark colouration of the Uranian satel- Hubble Space Telescope (HST) and Keck telescope inilites and rings.* [84] Uranus has relatively well developed tially observed neither a collar nor a polar cap in the
aurorae, which are seen as bright arcs around both mag- northern hemisphere.* [100] So Uranus appeared to be
netic poles.* [79] Unlike Jupiter's, Uranus's aurorae seem asymmetric: bright near the south pole and uniformly
to be insignificant for the energy balance of the planetary dark in the region north of the southern collar.* [100]
thermosphere.* [82]
In 2007, when Uranus passed its equinox, the southern collar almost disappeared, and a faint northern collar
emerged near 45° of latitude.* [102]
6.7 Climate
Main article: Climate of Uranus
At ultraviolet and visible wavelengths, Uranus's atmosphere is bland in comparison to the other giant planets, even to Neptune, which it otherwise closely resembles.* [17] When Voyager 2 flew by Uranus in 1986, it
observed a total of ten cloud features across the en-
In the 1990s, the number of the observed bright cloud
features grew considerably partly because new highresolution imaging techniques became available.* [17]
Most were found in the northern hemisphere as it started
to become visible.* [17] An early explanation—that bright
clouds are easier to identify in its dark part, whereas in
the southern hemisphere the bright collar masks them
– was shown to be incorrect.* [103]* [104] Neverthe-
88
CHAPTER 6. URANUS
The first dark spot observed on Uranus. Image obtained by the
HST ACS in 2006.
less there are differences between the clouds of each
hemisphere. The northern clouds are smaller, sharper
and brighter.* [104] They appear to lie at a higher altitude.* [104] The lifetime of clouds spans several orders
of magnitude. Some small clouds live for hours; at least
one southern cloud may have persisted since the Voyager
flyby.* [17]* [99] Recent observation also discovered that
cloud features on Uranus have a lot in common with those
on Neptune.* [17] For example, the dark spots common
on Neptune had never been observed on Uranus before Uranus in 2005. Rings, southern collar and a bright cloud in the
2006, when the first such feature dubbed Uranus Dark northern hemisphere are visible (HST ACS image).
Spot was imaged.* [105] The speculation is that Uranus is
becoming more Neptune-like during its equinoctial season.* [106]
km/h) and a persistent thunderstorm referred to as
The tracking of numerous cloud features allowed de- “Fourth of July fireworks”.* [99] On August 23, 2006,
termination of zonal winds blowing in the upper tropo- researchers at the Space Science Institute (Boulder, Colsphere of Uranus.* [17] At the equator winds are retro- orado) and the University of Wisconsin observed a dark
grade, which means that they blow in the reverse direc- spot on Uranus's surface, giving astronomers more insight
tion to the planetary rotation. Their speeds are from into Uranus's atmospheric activity.* [105] Why this sud−100 to −50 m/s.* [17]* [100] Wind speeds increase with den upsurge in activity occurred is not fully known, but it
the distance from the equator, reaching zero values near appears that Uranus's extreme axial tilt results in extreme
±20° latitude, where the troposphere's temperature mini- seasonal variations in its weather.* [51]* [106] Determinmum is located.* [17]* [64] Closer to the poles, the winds ing the nature of this seasonal variation is difficult beshift to a prograde direction, flowing with Uranus's rota- cause good data on Uranus's atmosphere have existed for
tion. Wind speeds continue to increase reaching maxima less than 84 years, or one full Uranian year. Photometry
at ±60° latitude before falling to zero at the poles.* [17] over the course of half a Uranian year (beginning in the
Wind speeds at −40° latitude range from 150 to 200 m/s. 1950s) has shown regular variation in the brightness in
Because the collar obscures all clouds below that parallel, two spectral bands, with maxima occurring at the solspeeds between it and the southern pole are impossible stices and minima occurring at the equinoxes.* [109] A
to measure.* [17] In contrast, in the northern hemisphere similar periodic variation, with maxima at the solstices,
maximum speeds as high as 240 m/s are observed near has been noted in microwave measurements of the deep
troposphere begun in the 1960s.* [110] Stratospheric
+50° latitude.* [17]* [100]* [107]
temperature measurements beginning in the 1970s also
showed maximum values near the 1986 solstice.* [78]
The majority of this variability is believed to occur owing
6.7.2 Seasonal variation
to changes in the viewing geometry.* [103]
For a short period from March to May 2004, large
clouds appeared in the Uranian atmosphere, giving it a
Neptune-like appearance.* [104]* [108] Observations included record-breaking wind speeds of 229 m/s (824
There are some reasons to believe that physical seasonal
changes are happening in Uranus. Although Uranus is
known to have a bright south polar region, the north pole
is fairly dim, which is incompatible with the model of
6.9. MOONS
the seasonal change outlined above.* [106] During its previous northern solstice in 1944, Uranus displayed elevated levels of brightness, which suggests that the north
pole was not always so dim.* [109] This information implies that the visible pole brightens some time before the
solstice and darkens after the equinox.* [106] Detailed
analysis of the visible and microwave data revealed that
the periodical changes of brightness are not completely
symmetrical around the solstices, which also indicates a
change in the meridional albedo patterns.* [106] In the
1990s, as Uranus moved away from its solstice, Hubble and ground-based telescopes revealed that the south
polar cap darkened noticeably (except the southern collar, which remained bright),* [101] whereas the northern
hemisphere demonstrated increasing activity,* [99] such
as cloud formations and stronger winds, bolstering expectations that it should brighten soon.* [104] This indeed
happened in 2007 when it passed an equinox: a faint
northern polar collar arose, and the southern collar became nearly invisible, although the zonal wind profile remained slightly asymmetric, with northern winds being
somewhat slower than southern.* [102]
89
larger they became; the larger they became, the more gas
they held onto until a critical point was reached, and their
size began to increase exponentially. The ice giants, with
only a few Earth masses of nebular gas, never reached
that critical point.* [112]* [113]* [114] Recent simulations
of planetary migration have suggested that both ice giants
formed closer to the Sun than their present positions, and
moved outwards after formation (the Nice model).* [112]
6.9 Moons
Main article: Moons of Uranus
See also: Timeline of discovery of Solar System planets
and their natural satellites
Uranus has 27 known natural satellites.* [114] The names
The mechanism of these physical changes is still not
clear.* [106] Near the summer and winter solstices,
Uranus's hemispheres lie alternately either in full glare of Major moons of Uranus in order of increasing distance (left to
right), at their proper relative sizes and albedos (collage of Voythe Sun's rays or facing deep space. The brightening of
ager 2 photographs)
the sunlit hemisphere is thought to result from the local
thickening of the methane clouds and haze layers located
in the troposphere.* [101] The bright collar at −45° latitude is also connected with methane clouds.* [101] Other
changes in the southern polar region can be explained
by changes in the lower cloud layers.* [101] The variation of the microwave emission from Uranus is probably
caused by changes in the deep tropospheric circulation,
because thick polar clouds and haze may inhibit convection.* [111] Now that the spring and autumn equinoxes
are arriving on Uranus, the dynamics are changing and
convection can occur again.* [99]* [111]
6.8 Formation
Main article: Formation and evolution of the Solar
System
For details of the evolution of Uranus's orbit, see Nice
model.
The Uranus System (NACO/VLT image)
Many argue that the differences between the ice giants
and the gas giants extend to their formation.* [112]* [113]
The Solar System is believed to have formed from a giant rotating ball of gas and dust known as the presolar
nebula. Much of the nebula's gas, primarily hydrogen
and helium, formed the Sun, and the dust grains collected together to form the first protoplanets. As the
planets grew, some of them eventually accreted enough
matter for their gravity to hold on to the nebula's leftover gas.* [112]* [113] The more gas they held onto, the
of these satellites are chosen from characters in the works
of Shakespeare and Alexander Pope.* [58]* [115] The five
main satellites are Miranda, Ariel, Umbriel, Titania, and
Oberon.* [58] The Uranian satellite system is the least
massive among those of the giant planets; the combined
mass of the five major satellites would be less than half
that of Triton (largest moon of Neptune) alone.* [9] The
largest of Uranus's satellites, Titania, has a radius of only
788.9 km, or less than half that of the Moon, but slightly
90
more than Rhea, the second-largest satellite of Saturn,
making Titania the eighth-largest moon in the Solar System. Uranus's satellites have relatively low albedos; ranging from 0.20 for Umbriel to 0.35 for Ariel (in green
light).* [16] They are ice–rock conglomerates composed
of roughly 50% ice and 50% rock. The ice may include
ammonia and carbon dioxide.* [84]* [116]
CHAPTER 6. URANUS
In 1986, NASA's Voyager 2 interplanetary probe encountered Uranus. This flyby remains the only investigation
of Uranus carried out from a short distance and no other
visits are planned. Launched in 1977, Voyager 2 made its
closest approach to Uranus on January 24, 1986, coming
within 81,500 kilometres of the cloudtops, before continuing its journey to Neptune. Voyager 2 studied the
structure and chemical composition of Uranus's atmosphere,* [70] including its unique weather, caused by its
axial tilt of 97.77°. It made the first detailed investigations of its five largest moons and discovered 10 new
ones. It examined all nine of the system's known rings
and discovered two more.* [16]* [84]* [123] It also studied the magnetic field, its irregular structure, its tilt and
its unique corkscrew magnetotail caused by Uranus's sideways orientation.* [92]
Among the Uranian satellites, Ariel appears to have
the youngest surface with the fewest impact craters
and Umbriel's the oldest.* [16]* [84] Miranda possesses
fault canyons 20 kilometres deep, terraced layers, and a
chaotic variation in surface ages and features.* [16] Miranda's past geologic activity is believed to have been
driven by tidal heating at a time when its orbit was more
eccentric than currently, probably as a result of a former
3:1 orbital resonance with Umbriel.* [117] Extensional
processes associated with upwelling diapirs are the likely
origin of Miranda's 'racetrack'-like coronae.* [118]* [119] The possibility of sending the Cassini spacecraft from
Ariel is believed to have once been held in a 4:1 resonance Saturn to Uranus was evaluated during a mission extenwith Titania.* [120]
sion planning phase in 2009.* [124] It would take about
Uranus possesses at least one horseshoe orbiter occu- twenty years to get to the Uranian system after departpying the Sun–Uranus L3 Lagrangian point —a grav- ing Saturn.* [124] A Uranus orbiter and probe was recitationally unstable region at 180º in its orbit, 83982 ommended by the 2013–2022 Planetary Science Decadal
Crantor.* [121]* [122] Crantor moves inside Uranus's co- Survey published in 2011; the proposal envisages launch
orbital region on a complex, temporary horseshoe orbit. during 2020–2023 and a 13-year cruise to Uranus.* [125]
2010 EU65 is also a promising Uranus horseshoe librator A Uranus entry probe could use Pioneer Venus Multicandidate.* [122]
probe heritage and descend to 1–5 atmospheres.* [125]
The ESA evaluated a “medium-class”mission called
Uranus Pathfinder.* [126] A New Frontiers Uranus Orbiter has been evaluated and recommended in the study,
6.10 Exploration
The Case for a Uranus Orbiter.* [127] Such a mission is
aided by the ease with which a relatively big mass can be
sent to the system—over 1500 kg with an Atlas 521 and
12-year journey.* [128] For more concepts see Proposed
Uranus missions.
6.11 In culture
In astrology, the planet Uranus (
) is the ruling planet
of Aquarius. Because Uranus is cyan and Uranus is associated with electricity, the colour electric blue, which is
close to cyan, is associated with the sign Aquarius* [129]
(see Uranus in astrology).
The chemical element uranium, discovered in 1789 by the
German chemist Martin Heinrich Klaproth, was named
after the newly discovered planet Uranus.* [130]
“Uranus, the Magician" is a movement in Gustav Holst's
The Planets, written between 1914 and 1916.
Operation Uranus was the successful military operation in
World War II by the Soviet army to take back Stalingrad
and marked the turning point in the land war against the
Crescent Uranus as imaged by Voyager 2 while en route to Nep- Wehrmacht.
tune
Main article: Exploration of Uranus
The lines “Then felt I like some watcher of the
skies/When a new planet swims into his ken”, from John
6.14. REFERENCES
Keats's "On First Looking Into Chapman's Homer", are
a reference to Herschel's discovery of Uranus.* [131]
6.12 See also
• 2011 QF99, the only known Uranus trojan
• Colonization of Uranus
• Uranus in astrology
• Uranus in fiction
91
[4] Because, in the English-speaking world, the latter sounds
like“your anus", the former pronunciation also saves embarrassment: as Pamela Gay, an astronomer at Southern
Illinois University Edwardsville, noted on her podcast, to
avoid “being made fun of by any small schoolchildren
... when in doubt, don't emphasise anything and just say
/ˈjʊərənəs/. And then run, quickly.”* [40]
[5] Cf.
(not supported by all fonts)
[6] Cf.
(not supported by all fonts)
[7] Mixing ratio is defined as the number of molecules of a
compound per a molecule of hydrogen.
6.13 Notes
[1] Orbital elements refer to the Uranus barycentre and Solar
System Barycentre. They are the instantaneous osculating
values at the precise J2000 epoch. Barycentre quantities
are given because, in contrast to the planetary centre, they
do not experience appreciable changes on a day-to-day basis from the motion of the moons.
[2] Refers to the level of 1 bar atmospheric pressure.
[3] Calculated using data from Seidelmann, 2007.* [8] omicalCircumference 159354.1 km* [4]
Surface area
8.1156×109 km2* [4]* [lower-alpha 2]
15.91 EarthsVolume 6.833×1013 km3* [6]* [lower-alpha
2]
63.086 EarthsMass (8.6810±0.0013)×1025 kg
14.536 Earths* [9]
GM=5793939±13 km3 /s2
Mean density
1.27 g/cm3* [6]* [lower-alpha 2]
Surface gravity
8.69 m/s2* [6]* [lower-alpha 2]
0.886 g
Escape velocity
21.3 km/s* [6]* [lower-alpha 2]
Sidereal rotation period
0.71833 d (Retrograde)
17 h 14 min 24 s* [8]
Equatorial rotation velocity
2.59 km/s
9,320 km/h
Axial tilt
97.77°* [8]
North pole right ascension
17* h 9* m 15* s
257.311°* [8]
North pole declination
−15.175°* [8]Albedo 0.300 (Bond)
0.51 (geom.)* [6]
Apparent magnitude
5.9* [12] to 5.32* [6]
Angular diameter
3.3″ to 4.1″* [6]Atmosphere* [11]* [13]* [14]covered element [[uranium Calculation of He, H2 and CH4 molar
fractions is based on a 2.3% mixing ratio of methane to
hydrogen and the 15/85 He/H2 proportions measured at
the tropopause.
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Ahue, W. M.; de Pater, I.; Rages, K. A.; Showal- [114] Sheppard, S. S.; Jewitt, D.; Kleyna, J. (2005). “An Ulter, M. R.; van Dam, M. A. (September 2009).
tradeep Survey for Irregular Satellites of Uranus: Limits
“Uranus at equinox: Cloud morphology and dynamics”.
to Completeness”. The Astronomical Journal 129: 518.
Icarus 203 (1): 265–286. Bibcode:2009Icar..203..265S.
doi:10.1086/426329.
doi:10.1016/j.icarus.2009.04.015.
[115] “Uranus”. nineplanets.org. Retrieved July 3, 2007.
[103] Karkoschka, Erich (May 2001).
“Uranus' Apparent Seasonal Variability in 25 HST Filters”. [116] Hussmann, Hauke; Sohl, Frank; Spohn, Tilman (2006).
Icarus 151 (1): 84–92. Bibcode:2001Icar..151...84K.
“Subsurface oceans and deep interiors of medium-sized
doi:10.1006/icar.2001.6599.
outer planet satellites and large trans-neptunian objects”
. Icarus 185: 258–273. Bibcode:2006Icar..185..258H.
[104] Hammel, H. B.; Depater, I.; Gibbard, S. G.; Lockdoi:10.1016/j.icarus.2006.06.005.
wood, G. W.; Rages, K. (May 2005).
“New
cloud activity on Uranus in 2004: First detection [117] Tittemore, William C.; Wisdom, Jack (June 1990).
“Tidal evolution of the Uranian satellites: III. Evoluof a southern feature at 2.2 µm” (PDF). Icarus
tion through the Miranda-Umbriel 3:1, Miranda-Ariel 5:3,
175 (1): 284–288.
Bibcode:2005Icar..175..284H.
and Ariel-Umbriel 2:1 mean-motion commensurabilities”
doi:10.1016/j.icarus.2004.11.016.
. Icarus 85 (2): 394–443. Bibcode:1990Icar...85..394T.
[105] Sromovsky, L.; Fry, P.;Hammel, H. and Rages, K.“Hubdoi:10.1016/0019-1035(90)90125-S.
ble Discovers a Dark Cloud in the Atmosphere of Uranus”
[118] Pappalardo, R. T., Reynolds, S. J., Greeley, R.
(PDF). physorg.com. Retrieved August 22, 2007.
(1997). “Extensional tilt blocks on Miranda: Ev[106] Hammel, H.B.; Lockwood, G.W. (2007). “Longidence for an upwelling origin of Arden Corona”
term atmospheric variability on Uranus and Neptune”
.
Journal of Geophysical Research 102 (E6):
Bibcode:1997JGR...10213369P.
. Icarus 186: 291–301. Bibcode:2007Icar..186..291H.
13,369–13,380.
doi:10.1016/j.icarus.2006.08.027.
doi:10.1029/97JE00802.
96
CHAPTER 6. URANUS
[119] Chaikin, Andrew (October 16, 2001). “Birth of Uranus'
Provocative Moon Still Puzzles Scientists”. Space.Com.
ImaginovaCorp. Archived from the original on 2008-0709. Retrieved December 7, 2007.
• NASA's Uranus fact sheet
[120] Tittemore, W. C. (September 1990).
“Tidal
heating of Ariel”.
Icarus 87 (1): 110–139.
Bibcode:1990Icar...87..110T.
doi:10.1016/00191035(90)90024-4.
• Planets – Uranus A kid's guide to Uranus.
[121] Gallardo, T. (2006).
“Atlas of the mean motion resonances in the Solar System”.
Icarus
184 (1):
29–38.
Bibcode:2006Icar..184...29G.
doi:10.1016/j.icarus.2006.04.001.
• Voyager at Uranus (photos)
[122] de la Fuente Marcos, C. and de la Fuente Marcos, R.
(2013). “Crantor, a short-lived horseshoe companion
to Uranus”. Astronomy and Astrophysics 551: A114.
arXiv:1301.0770. Bibcode:2013A%26A...551A.114D.
doi:10.1051/0004-6361/201220646.
• Gray, Meghan; Merrifield, Michael (2010).
“Uranus”. Sixty Symbols. Brady Haran for the
University of Nottingham.
[123] “Voyager: The Interstellar Mission: Uranus”. JPL. 2004.
Retrieved June 9, 2007.
[124] Pappalardo, Bob and Spiker, Linda (2009-03-09).
“Cassini Proposed Extended-Extended Mission (XXM)"
(PDF). Retrieved 2011-08-20.
[125] Space Studies Board. “NRC planetary decadal survey
2013–2022”. NASA Lunar Science Institute. Retrieved
2011-08-05.
[126] Michael Schirber – Missions Proposed to Explore Mysterious Tilted Planet Uranus (2011) – Astrobiology
Magazine. Space.com. Retrieved on 2012-04-02.
[127] THE CASE FOR A URANUS ORBITER, Mark Hofstadter et al.
[128] To Uranus on Solar Power and Batteries. (PDF) . Retrieved on 2012-04-02.
[129] Parker, Derek and Julia Aquarius. Planetary Zodiac Library. New York: Mitchell Beazley/Ballantine Book.
1972. p. 14.
[130] “Uranium”. The American Heritage Dictionary of the
English Language (4th ed.). Houghton Mifflin Company.
Retrieved April 20, 2010.
[131] “On First Looking Into Chapman's Homer”. City University of New York. 2009. Retrieved 2011-10-29.
6.15 Further reading
• Miner, Ellis D. (1998). Uranus: The Planet, Rings
and Satellites. New York: John Wiley and Sons.
ISBN 978-0-471-97398-0.
6.16 External links
• Uranus at European Space Agency
• Uranus Profile at NASA's Solar System Exploration
site
• Uranus at Jet Propulsion Laboratory's planetary
photojournal. (photos)
• Uranus (Astronomy Cast homepage) (blog)
• Uranian system montage (photo)
Chapter 7
Venus
This article is about the planet. For other uses, see Venus
(disambiguation).
Venus is the second planet from the Sun, orbiting it every
224.7 Earth days.* [10] It has no natural satellite. It is
named after the Roman goddess of love and beauty. After
the Moon, it is the brightest natural object in the night sky,
reaching an apparent magnitude of −4.6, bright enough
to cast shadows.* [11] Because Venus is an inferior planet
from Earth, it never appears to venture far from the Sun:
its elongation reaches a maximum of 47.8°.
Venus is a terrestrial planet and is sometimes called
Earth's “sister planet”because of their similar size,
mass, proximity to the Sun and bulk composition. It
is radically different from Earth in other respects. It
has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The
atmospheric pressure at the planet's surface is 92 times
that of Earth's. With a mean surface temperature of 735
K (462 °C; 863 °F), Venus is by far the hottest planet in
the Solar System, even though Mercury is closer to the
Sun. Venus has no carbon cycle that puts carbon into
rock, nor does it seem to have any organic life to absorb carbon in biomass. Venus is shrouded by an opaque
layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light.
It may have possessed oceans in the past,* [12]* [13] but
these would have vaporized as the temperature rose due
to a runaway greenhouse effect.* [14] The water has most
probably photodissociated, and, because of the lack of
a planetary magnetic field, the free hydrogen has been
swept into interplanetary space by the solar wind.* [15]
Venus' surface is a dry desertscape interspersed with slablike rocks and periodically refreshed by volcanism.
Size comparison of Mercury, Venus, Earth and the Moon, Mars,
and Ceres on the far right. This may not be exactly to scale,
because the visual disc of Venus with its atmosphere makes it
look bigger than its solid-body diameter.
Size comparison with Earth.
surface differ radically from those on Earth, owing to its
dense carbon dioxide atmosphere. The mass of the atmosphere of Venus is 96.5% carbon dioxide, with most of
the remaining 3.5% being nitrogen.* [17]
7.1.1 Geography
The Venusian surface was a subject of speculation until some of its secrets were revealed by planetary science
in the 20th century. It was finally mapped in detail by
Project Magellan in 1990–91. The ground shows evidence of extensive volcanism, and the sulfur in the atmo7.1 Physical characteristics
sphere may indicate there have been some recent erup*
*
Venus is one of the four terrestrial planets in the Solar tions. [18] [19]
System, meaning that, like Earth, it is a rocky body. In About 80% of the Venusian surface is covered by smooth,
size and mass, it is similar to Earth, and is often described volcanic plains, consisting of 70% plains with wrinas Earth's “sister”or “twin”.* [16] The diameter of kle ridges and 10% smooth or lobate plains.* [20] Two
Venus is 12,092 km (only 650 km less than Earth's) and highland“continents”make up the rest of its surface area,
its mass is 81.5% of Earth's. Conditions on the Venusian one lying in the planet's northern hemisphere and the
97
98
CHAPTER 7. VENUS
other just south of the equator. The northern continent
is called Ishtar Terra, after Ishtar, the Babylonian goddess of love, and is about the size of Australia. Maxwell
Montes, the highest mountain on Venus, lies on Ishtar
Terra. Its peak is 11 km above the Venusian average surface elevation. The southern continent is called
Aphrodite Terra, after the Greek goddess of love, and is
the larger of the two highland regions at roughly the size
of South America. A network of fractures and faults covers much of this area.* [21]
The absence of evidence of lava flow accompanying any
of the visible caldera remains an enigma. The planet
has few impact craters, demonstrating the surface is
relatively young, approximately 300–600 million years
old.* [22]* [23] In addition to the impact craters, mountains, and valleys commonly found on rocky planets,
Venus has some unique surface features. Among these
are flat-topped volcanic features called "farra", which
look somewhat like pancakes and range in size from 20 to
50 km across, and from 100 to 1,000 m high; radial, starlike fracture systems called “novae"; features with both
radial and concentric fractures resembling spider webs,
known as "arachnoids"; and“coronae”, circular rings of
fractures sometimes surrounded by a depression. These
features are volcanic in origin.* [24]
Most Venusian surface features are named after historical
and mythological women.* [25] Exceptions are Maxwell
Montes, named after James Clerk Maxwell, and highland regions Alpha Regio, Beta Regio and Ovda Regio.
The former three features were named before the current system was adopted by the International Astronomical Union, the body that oversees planetary nomenclature.* [26]
The longitudes of physical features on Venus are expressed relative to its prime meridian. The original prime
meridian passed through the radar-bright spot at the center of the oval feature Eve, located south of Alpha Regio.* [27] After the Venera missions were completed, the
prime meridian was redefined to pass through the central
peak in the crater Ariadne.* [28]* [29]
7.1.2
Surface geology
Main article: Geology of Venus
Much of the Venusian surface appears to have been
shaped by volcanic activity. Venus has several times
as many volcanoes as Earth, and it possesses 167 large
volcanoes that are over 100 km across. The only volcanic complex of this size on Earth is the Big Island
of Hawaii.* [24] This is not because Venus is more volcanically active than Earth, but because its crust is
older. Earth's oceanic crust is continually recycled by
subduction at the boundaries of tectonic plates, and has
an average age of about 100 million years,* [30] whereas
the Venusian surface is estimated to be 300–600 million
years old.* [22]* [24]
Maat Mons with a vertical exaggeration of 22.5
Several lines of evidence point to ongoing volcanic activity on Venus. During the Soviet Venera program, the
Venera 11 and Venera 12 probes detected a constant
stream of lightning, and Venera 12 recorded a powerful clap of thunder soon after it landed. The European
Space Agency's Venus Express recorded abundant lightning in the high atmosphere.* [31] Although rainfall drives
thunderstorms on Earth, there is no rainfall on the surface
of Venus (though sulfuric acid rain falls in the upper atmosphere, then evaporates around 25 km above the surface). One possibility is that ash from a volcanic eruption
was generating the lightning. Another piece of evidence
comes from measurements of sulfur dioxide concentrations in the atmosphere, which dropped by a factor of 10
between 1978 and 1986. This may mean the levels had
earlier been boosted by a large volcanic eruption.* [32]
Almost a thousand impact craters on Venus are evenly
distributed across its surface. On other cratered bodies,
such as Earth and the Moon, craters show a range of states
of degradation. On the Moon, degradation is caused by
subsequent impacts, whereas on Earth it is caused by wind
and rain erosion. On Venus, about 85% of the craters
are in pristine condition. The number of craters, together with their well-preserved condition, indicates the
planet underwent a global resurfacing event about 300–
600 million years ago,* [22]* [23] followed by a decay in
volcanism.* [33] Whereas Earth's crust is in continuous
motion, Venus is thought to be unable to sustain such a
process. Without plate tectonics to dissipate heat from
its mantle, Venus instead undergoes a cyclical process in
which mantle temperatures rise until they reach a critical level that weakens the crust. Then, over a period of
about 100 million years, subduction occurs on an enormous scale, completely recycling the crust.* [24] In March
2014, the first direct evidence for ongoing volcanism was
located, in the form of infrared “flashes”over the rift
zone Ganiki Chasma, near the shield volcano Maat Mons.
These flashes, ranging from 40 to 320 °C above the ambient, are believed to be either hot gases or lava released
from volcanic eruptions.* [34]
7.1. PHYSICAL CHARACTERISTICS
99
Venusian craters range from 3 km to 280 km in diameter. 7.1.4
No craters are smaller than 3 km, because of the effects
of the dense atmosphere on incoming objects. Objects
with less than a certain kinetic energy are slowed down
so much by the atmosphere that they do not create an impact crater.* [35] Incoming projectiles less than 50 metres
in diameter will fragment and burn up in the atmosphere
before reaching the ground.* [36]
7.1.3
Atmosphere and climate
Internal structure
Cloud structure in the Venusian atmosphere in 1979,
revealed by observations in the ultraviolet band by
Pioneer Venus Orbiter
The internal structure of Venus – the crust (outer layer), the mantle (middle layer) and the core (yellow inner layer)
Without seismic data or knowledge of its moment of inertia, little direct information is available about the internal
structure and geochemistry of Venus.* [37] The similarity in size and density between Venus and Earth suggests
they share a similar internal structure: a core, mantle, and
crust. Like that of Earth, the Venusian core is at least
partially liquid because the two planets have been cooling at about the same rate.* [38] The slightly smaller size
of Venus suggests pressures are significantly lower in its
deep interior than Earth. The principal difference between the two planets is the lack of evidence for plate tectonics on Venus, possibly because its crust is too strong
to subduct without water to make it less viscous. This
results in reduced heat loss from the planet, preventing
it from cooling and providing a likely explanation for its
lack of an internally generated magnetic field.* [39] Instead, Venus may lose its internal heat in periodic major
resurfacing events.* [22]
Global radar view of Venus (without the clouds) from
the Magellan imaging between 1990 and 1994
Impact craters on the surface of Venus (image reconstructed from radar data)
Main article: Atmosphere of Venus
Venus has an extremely dense atmosphere, which consists mainly of carbon dioxide and a small amount of
nitrogen. The atmospheric mass is 93 times that of
Earth's atmosphere, whereas the pressure at the planet's
surface is about 92 times that at Earth's surface—a pres-
100
sure equivalent to that at a depth of nearly 1 kilometre
under Earth's oceans. The density at the surface is 65
kg/m3 , 6.5% that of water or 50 times as dense as Earth's
atmosphere at 20 °C at sea level. The CO2 -rich atmosphere, along with thick clouds of sulfur dioxide, generates the strongest greenhouse effect in the Solar System, creating surface temperatures of at least 735 K (462
°C).* [10]* [40] This makes the Venusian surface hotter
than Mercury's, which has a minimum surface temperature of 55 K (−220 °C) and maximum surface temperature of 695 K (420 °C),* [41] even though Venus is
nearly twice Mercury's distance from the Sun and thus
receives only 25% of Mercury's solar irradiance. The
surface of Venus is often described as hellish.* [42] This
temperature is higher than temperatures used to achieve
sterilization.
Studies have suggested that billions of years ago the Venusian atmosphere was much more like Earth's than it is
now, and that there may have been substantial quantities
of liquid water on the surface, but after a period of 600
million to several billion years,* [43] a runaway greenhouse effect was caused by the evaporation of that original water, which generated a critical level of greenhouse
gases in its atmosphere.* [44] Although the surface conditions on the planet are no longer hospitable to any Earthlike life that may have formed before this event, it is possible that life exists in the lower and middle cloud layers
of Venus.* [45]* [46]* [47]
CHAPTER 7. VENUS
—also minimizes seasonal temperature variation.* [54]
The only appreciable variation in temperature occurs with
altitude. The highest point on Venus, Maxwell Montes, is
therefore the coolest point on the planet, with a temperature of about 655 K (380 °C) and an atmospheric pressure of about 4.5 MPa (45 bar).* [55]* [56] In 1995, the
Magellan probe imaged a highly reflective substance at
the tops of the highest mountain peaks that bore a strong
resemblance to terrestrial snow. This substance arguably
formed from a similar process to snow, albeit at a far
higher temperature. Too volatile to condense on the surface, it rose in gas form to cooler higher elevations, where
it then fell as precipitation. The identity of this substance
is not known with certainty, but speculation has ranged
from elemental tellurium to lead sulfide (galena).* [57]
The clouds of Venus are capable of producing lightning
much like the clouds on Earth.* [58] The existence of
lightning had been controversial since the first suspected bursts were detected by the Soviet Venera
probes. In 2006–2007 Venus Express clearly detected
whistler mode waves, the signatures of lightning. Their
intermittent appearance indicates a pattern associated
with weather activity. The lightning rate is at least half
of that on Earth.* [58] In 2007 the Venus Express probe
discovered that a huge double atmospheric vortex exists
at the south pole.* [59]* [60]
Another discovery made by the Venus Express probe in
2011 is that an ozone layer exists high in the atmosphere
Thermal inertia and the transfer of heat by winds in the of Venus.* [61]
lower atmosphere mean that the temperature of the Venu- On January 29, 2013, ESA scientists reported that the
sian surface does not vary significantly between the night ionosphere of the planet Venus streams outwards in a
and day sides, despite the planet's extremely slow rota- manner similar to “the ion tail seen streaming from a
tion. Winds at the surface are slow, moving at a few kilo- comet under similar conditions.”* [62]* [63]
metres per hour, but because of the high density of the
atmosphere at the Venusian surface, they exert a signifi- Atmospheric composition
cant amount of force against obstructions, and transport
dust and small stones across the surface. This alone would
make it difficult for a human to walk through, even if
the heat, pressure and lack of oxygen were not a problem.* [48]
Above the dense CO2 layer are thick clouds consisting mainly of sulfur dioxide and sulfuric acid
droplets.* [49]* [50] These clouds reflect and scatter about
90% of the sunlight that falls on them back into space,
and prevent visual observation of the Venusian surface.
The permanent cloud cover means that although Venus is Synthetic stick absorption spectrum of a simple gas mixcloser than Earth to the Sun, the Venusian surface is not as ture corresponding to Earth's atmosphere
well lit. Strong 85 m/s (300 km/h) winds at the cloud tops
circle the planet about every four to five Earth days.* [51]
Venusian winds move at up to 60 times the speed of the
planet's rotation, whereas Earth's fastest winds are only
10–20% rotation speed.* [52]
The surface of Venus is effectively isothermal; it retains a
constant temperature not only between day and night but
between the equator and the poles.* [1]* [53] The planet's
minute axial tilt—less than 3°, compared to 23° on Earth
7.2. ORBIT AND ROTATION
101
Venusian atmosphere composition based on HITRAN mosphere by 150 times compared to the ratio in the lower
data* [64] created using Hitran on the Web system.* [65] atmosphere.* [73]
Green colour – water vapour, red – carbon dioxide, WN
– wavenumber (other colours have different meanings,
lower wavelengths on the right, higher on the left).
7.2 Orbit and rotation
7.1.5
Magnetic field and core
In 1967, Venera 4 found the Venusian magnetic field to
be much weaker than that of Earth. This magnetic field is
induced by an interaction between the ionosphere and the
solar wind,* [66]* [67] rather than by an internal dynamo
in the core like the one inside Earth. Venus's small
induced magnetosphere provides negligible protection to
the atmosphere against cosmic radiation. This radiation
may result in cloud-to-cloud lightning discharges.* [68]
The lack of an intrinsic magnetic field at Venus was surprising given it is similar to Earth in size, and was expected also to contain a dynamo at its core. A dynamo
requires three things: a conducting liquid, rotation, and
convection. The core is thought to be electrically conductive and, although its rotation is often thought to be
too slow, simulations show it is adequate to produce a
dynamo.* [69]* [70] This implies the dynamo is missing
because of a lack of convection in the Venusian core. On
Earth, convection occurs in the liquid outer layer of the
core because the bottom of the liquid layer is much hotter
than the top. On Venus, a global resurfacing event may
have shut down plate tectonics and led to a reduced heat
flux through the crust. This caused the mantle temperature to increase, thereby reducing the heat flux out of the
core. As a result, no internal geodynamo is available to
drive a magnetic field. Instead, the heat energy from the
core is being used to reheat the crust.* [71]
One possibility is that Venus has no solid inner core,* [72]
or that its core is not cooling, so that the entire liquid
part of the core is at approximately the same temperature. Another possibility is that its core has already completely solidified. The state of the core is highly dependent on the concentration of sulfur, which is unknown at
present.* [71]
The weak magnetosphere around Venus means that the
solar wind is interacting directly with its outer atmosphere. Here, ions of hydrogen and oxygen are being
created by the dissociation of neutral molecules from ultraviolet radiation. The solar wind then supplies energy
that gives some of these ions sufficient velocity to escape Venus's gravity field. This erosion process results
in a steady loss of low-mass hydrogen, helium, and oxygen ions, whereas higher-mass molecules, such as carbon
dioxide, are more likely to be retained. Atmospheric erosion by the solar wind probably led to the loss of most
of Venus's water during the first billion years after it
formed. The erosion has increased the ratio of highermass deuterium to lower-mass hydrogen in the upper at-
Venus orbits the Sun at an average distance of about 108 million
kilometres (about 0.7 AU) and completes an orbit every 224.65
days. Venus is the second planet from the Sun and orbits the Sun
approximately 1.6 times (yellow trail) in Earth's 365 days (blue
trail)
Venus orbits the Sun at an average distance of about 0.72
AU (108,000,000 km; 67,000,000 mi), and completes an
orbit every 224.65 days. Although all planetary orbits are
elliptical, Venus's orbit is the closest to circular, with an
eccentricity of less than 0.01.* [1] When Venus lies between Earth and the Sun, a position known as inferior
conjunction, it makes the closest approach to Earth of
any planet at an average distance of 41 million km.* [1]
The planet reaches inferior conjunction every 584 days,
on average.* [1] Owing to the decreasing eccentricity of
Earth's orbit, the minimum distances will become greater
over tens of thousands of years. From the year 1 to 5383,
there are 526 approaches less than 40 million km; then
there are none for about 60,158 years.* [74]
All the planets of the Solar System orbit the Sun in an
anti-clockwise direction as viewed from above Earth's
north pole. Most planets also rotate on their axes in
an anti-clockwise direction, but Venus rotates clockwise (called "retrograde" rotation) once every 243 Earth
days —the slowest rotation period of any planet. Because its rotation is so slow, it is highly spherical.* [75]
A Venusian sidereal day thus lasts longer than a Venusian year (243 versus 224.7 Earth days). Venus's equator rotates at 6.5 km/h (4.0 mph), whereas Earth's is approximately 1,670 km/h (1,040 mph).* [76] Venus's rotation has slowed down by 6.5 min per Venusian sidereal
day in the 16 years between the Magellan spacecraft and
102
CHAPTER 7. VENUS
Venus Express visits.* [77] Because of the retrograde rotation, the length of a solar day on Venus is significantly
shorter than the sidereal day, at 116.75 Earth days (making the Venusian solar day shorter than Mercury's 176
Earth days); one Venusian year is about 1.92 Venusian
(solar) days long.* [78] To an observer on the surface of
Venus, the Sun would rise in the west and set in the east,
though the Sun cannot be seen from the surface due to
Venus's opaque clouds.* [78]
Venus may have formed from the solar nebula with a different rotation period and obliquity, reaching its current
state because of chaotic spin changes caused by planetary
Venus is always brighter than the brightest stars outside the Solar
perturbations and tidal effects on its dense atmosphere, a System, as can be seen here over the Pacific Ocean
change that would have occurred over the course of billions of years. The rotation period of Venus may represent an equilibrium state between tidal locking to the
Sun's gravitation, which tends to slow rotation, and an atmospheric tide created by solar heating of the thick Venusian atmosphere.* [79]* [80] The 584-day average interval
between successive close approaches to Earth is almost
exactly equal to 5 Venusian solar days,* [81] but the hypothesis of a spin–orbit resonance with Earth has been
discounted.* [82]
Venus has no natural satellites,* [83] though the asteroid
2002 VE68 presently maintains a quasi-orbital relationship with it.* [84]* [85] Besides this quasi-satellite, it has
two other temporary co-orbitals, 2001 CK32 and 2012
XE133.* [86] In the 17th century, Giovanni Cassini reported a moon orbiting Venus, which was named Neith
and numerous sightings were reported over the following
200 years, but most were determined to be stars in the
vicinity. Alex Alemi's and David Stevenson's 2006 study
of models of the early Solar System at the California Institute of Technology shows Venus likely had at least one
moon created by a huge impact event billions of years
ago.* [87] About 10 million years later, according to the
study, another impact reversed the planet's spin direction
and caused the Venusian moon gradually to spiral inward
until it collided and merged with Venus.* [88] If later impacts created moons, these were absorbed in the same
way. An alternative explanation for the lack of satellites
is the effect of strong solar tides, which can destabilize
large satellites orbiting the inner terrestrial planets.* [83]
7.3 Observation
Venus is always brighter than any star (apart from the
Sun). The greatest luminosity, apparent magnitude
−4.9,* [8] occurs during crescent phase when it is near
Earth. Venus fades to about magnitude −3 when it is
backlit by the Sun.* [7] The planet is bright enough to be
seen in a mid-day clear sky,* [89] and it can be easy to see
when the Sun is low on the horizon. As an inferior planet,
it always lies within about 47° of the Sun.* [9]
Phases of Venus and evolution of its apparent diameter
Sun.* [1] As it does so, it changes from the “Evening
Star”, visible after sunset, to the “Morning Star”, visible before sunrise. Although Mercury, the other inferior
planet, reaches a maximum elongation of only 28° and
is often difficult to discern in twilight, Venus is hard to
miss when it is at its brightest. Its greater maximum elongation means it is visible in dark skies long after sunset.
As the brightest point-like object in the sky, Venus is a
commonly misreported "unidentified flying object". U.S.
President Jimmy Carter reported having seen a UFO in
1969, which later analysis suggested was probably Venus.
Countless other people have mistaken Venus for something more exotic.* [90]
As it moves around its orbit, Venus displays phases like
those of the Moon in a telescopic view. The planet
presents a small “full”image when it is on the opposite
side of the Sun. It shows a larger “quarter phase”when
it is at its maximum elongations from the Sun, and is at
its brightest in the night sky, and presents a much larger
“thin crescent”in telescopic views as it comes around to
the near side between Earth and the Sun. Venus is at its
Venus “overtakes”Earth every 584 days as it orbits the largest and presents its “new phase”when it is between
7.4. STUDIES
103
Earth and the Sun. Its atmosphere can be seen in a tele- 7.3.2 Ashen light
scope by the halo of light refracted around it.* [9]
A long-standing mystery of Venus observations is the socalled ashen light—an apparent weak illumination of its
dark side, seen when the planet is in the crescent phase.
The first claimed observation of ashen light was made in
7.3.1 Transits
1643, but the existence of the illumination has never been
reliably confirmed. Observers have speculated it may result from electrical activity in the Venusian atmosphere,
but it could be illusory, resulting from the physiological
effect of observing a bright, crescent-shaped object.* [97]
7.4 Studies
7.4.1 Early studies
2004 transit of Venus
Main articles: Transits of Venus and Transit of Venus,
2012
The Venusian orbit is slightly inclined relative to Earth's
orbit; thus, when the planet passes between Earth and the
Sun, it usually does not cross the face of the Sun. Transits
of Venus occur when the planet's inferior conjunction coincides with its presence in the plane of Earth's orbit.
Transits of Venus occur in cycles of 243 years with the
current pattern of transits being pairs of transits separated The "black drop effect" as recorded during the 1769 transit
by eight years, at intervals of about 105.5 years or 121.5
years—a pattern first discovered in 1639 by the English
Venus was known to ancient civilizations both as the
astronomer Jeremiah Horrocks.* [91]
“morning star”and as the “evening star”, names that
The latest pair was June 8, 2004 and June 5–6, 2012. The reflect the early assumption that these were two separate
transit could be watched live from many online outlets objects. The Venus tablet of Ammisaduqa, dated 1581
or observed locally with the right equipment and condi- BCE, shows the Babylonians understood the two were
tions.* [92]
a single object, referred to in the tablet as the “bright
The preceding pair of transits occurred in December queen of the sky”,* and could support this view with de1874 and December 1882; the following pair will occur in tailed observations. [98] The Greeks thought of the two
until the time
December 2117 and December 2125.* [93] Historically, as separate stars, Phosphorus and Hesperus,
*
Pythagoras
in
the
sixth
century
BC.
[99]
The Romans
of
transits of Venus were important, because they allowed
designated
the
morning
aspect
of
Venus
as
Lucifer,
literastronomers to determine the size of the astronomical
Vesper,
ally“Light-Bringer”,
and
the
evening
aspect
as
unit, and hence the size of the Solar System as shown
by Horrocks in 1639.* [94] Captain Cook's exploration both literal translations of the respective Greek names.
of the east coast of Australia came after he had sailed The transit of Venus was first observed in 1032 by the
to Tahiti in 1768 to observe a transit of Venus.* [95]* [96] Persian astronomer Avicenna, who concluded Venus is
104
CHAPTER 7. VENUS
closer to Earth than the Sun,* [100] and established Venus
was, at least sometimes, below the Sun.* [101] In the 12th
century, the Andalusian astronomer Ibn Bajjah observed
“two planets as black spots on the face of the Sun”, which
were later identified as the transits of Venus and Mercury
by the Maragha astronomer Qotb al-Din Shirazi in the
13th century.* [102] The transit of Venus was also observed by Jeremiah Horrocks on 4 December 1639 (24
November under the Julian calendar in use at that time),
along with his friend, William Crabtree, at each of their
respective homes.* [103]
Modern telescopic view of Venus from Earth's surface
7.4.2 Ground-based research
Little more was discovered about Venus until the 20th
century. Its almost featureless disc gave no hint what its
surface might be like, and it was only with the development of spectroscopic, radar and ultraviolet observations
that more of its secrets were revealed. The first UV obserEARTH
vations were carried out in the 1920s, when Frank E. Ross
found that UV photographs revealed considerable detail
Galileo's discovery that Venus showed phases (although remainthat was absent in visible and infrared radiation. He suging near the Sun in Earth's sky) proved that it orbits the Sun and
gested this was due to a dense, yellow lower atmosphere
not Earth
with high cirrus clouds above it.* [110]
Spectroscopic observations in the 1900s gave the first
clues about the Venusian rotation. Vesto Slipher tried
to measure the Doppler shift of light from Venus, but
found he could not detect any rotation. He surmised the
planet must have a much longer rotation period than had
previously been thought.* [111] Later work in the 1950s
showed the rotation was retrograde. Radar observations
of Venus were first carried out in the 1960s, and provided
the first measurements of the rotation period, which were
close to the modern value.* [112]
When the Italian physicist Galileo Galilei first observed
the planet in the early 17th century, he found it showed
phases like the Moon, varying from crescent to gibbous to
full and vice versa. When Venus is furthest from the Sun
in the sky, it shows a half-lit phase, and when it is closest
to the Sun in the sky, it shows as a crescent or full phase.
This could be possible only if Venus orbited the Sun, and
this was among the first observations to clearly contradict
the Ptolemaic geocentric model that the Solar System was
Radar observations in the 1970s revealed details of the
concentric and centered on Earth.* [104]* [105]
Venusian surface for the first time. Pulses of radio waves
The atmosphere of Venus was discovered in 1761 by Ruswere beamed at the planet using the 300 m (980 ft) ra*
*
sian polymath Mikhail Lomonosov. [106] [107] Venus's
dio telescope at Arecibo Observatory, and the echoes reatmosphere was observed in 1790 by German astronomer
vealed two highly reflective regions, designated the Alpha
Johann Schröter. Schröter found when the planet was a
and Beta regions. The observations also revealed a bright
thin crescent, the cusps extended through more than 180°.
region attributed to mountains, which was called Maxwell
He correctly surmised this was due to scattering of sunMontes.* [113] These three features are now the only ones
light in a dense atmosphere. Later, American astronomer
on Venus that do not have female names.* [114]
Chester Smith Lyman observed a complete ring around
the dark side of the planet when it was at inferior conjunction, providing further evidence for an atmosphere.* [108]
The atmosphere complicated efforts to determine a rota7.5 Exploration
tion period for the planet, and observers such as Italianborn astronomer Giovanni Cassini and Schröter incorrectly estimated periods of about 24 h from the motions Main article: Observations and explorations of Venus
of markings on the planet's apparent surface.* [109]
7.5. EXPLORATION
7.5.1
105
Early efforts
Mariner 2, launched in 1962
The first robotic space probe mission to Venus, and the
first to any planet, began on 12 February 1961, with the
launch of the Venera 1 probe. The first craft of the otherwise highly successful Soviet Venera program, Venera
1 was launched on a direct impact trajectory, but contact Pioneer Venus Multiprobe
was lost seven days into the mission, when the probe was
about 2 million km from Earth. It was estimated to have
reading was 18 bar at an altitude of 24.96 km.* [118]
passed within 100,000 km of Venus in mid-May.* [115]
One day later on 19 October 1967, Mariner 5 conducted
The United States exploration of Venus also started badly
a fly-by at a distance of less than 4000 km above the cloud
with the loss of the Mariner 1 probe on launch. The subtops. Mariner 5 was originally built as a backup for the
sequent Mariner 2 mission, after a 109-day transfer orbit
Mars-bound Mariner 4; when that mission was successon 14 December 1962, became the world's first successful, the probe was refitted for a Venus mission. A suite
ful interplanetary mission, passing 34,833 km above the
of instruments more sensitive than those on Mariner 2, in
surface of Venus. Its microwave and infrared radiometers
particular its radio occultation experiment, returned data
revealed that although the Venusian cloud tops were cool,
on the composition, pressure and density of the Venuthe surface was extremely hot—at least 425 °C, confirmsian atmosphere.* [119] The joint Venera 4 – Mariner
ing previous Earth-based measurements* [116] and finally
5 data was analysed by a combined Soviet-American
ending any hopes that the planet might harbour groundscience team in a series of colloquia over the followbased life. Mariner 2 also obtained improved estimates
ing year,* [120] in an early example of space cooperaof its mass and of the astronomical unit, but was unable
tion.* [121]
to detect either a magnetic field or radiation belts.* [117]
Armed with the lessons and data learned from Venera 4,
the Soviet Union launched the twin probes Venera 5 and
7.5.2 Atmospheric entry
Venera 6 five days apart in January 1969; they encountered Venus a day apart on 16 and 17 May. The probes
The Soviet Venera 3 probe crash-landed on Venus on 1 were strengthened to improve their crush depth to 25 bar
March 1966. It was the first man-made object to enter the and were equipped with smaller parachutes to achieve a
atmosphere and strike the surface of another planet. Its faster descent. Because then-current atmospheric models
communication system failed before it was able to return of Venus suggested a surface pressure of between 75 and
any planetary data.* [118] On 18 October 1967, Venera 4 100 bar, neither was expected to survive to the surface.
successfully entered the atmosphere and deployed science After returning atmospheric data for a little over 50 minexperiments. Venera 4 showed the surface temperature utes, they were both crushed at altitudes of approximately
was even hotter than Mariner 2 had measured, at almost 20 km before going on to strike the surface on the night
500 °C, and the atmosphere was 90 to 95% carbon diox- side of Venus.* [118]
ide. The Venusian atmosphere was considerably denser
than Venera 4's designers had anticipated, and its slower
than intended parachute descent meant its batteries ran 7.5.3 Surface and atmospheric science
down before the probe reached the surface. After returning descent data for 93 minutes, Venera 4's last pressure Venera 7 represented an effort to return data from the
106
planet's surface, and was constructed with a reinforced
descent module capable of withstanding a pressure of
180 bar. The module was precooled before entry and
equipped with a specially reefed parachute for a rapid 35minute descent. While entering the atmosphere on 15
December 1970, the parachute is believed to have partially torn, and the probe struck the surface with a hard,
yet not fatal, impact. Probably tilted onto its side, it returned a weak signal, supplying temperature data for 23
minutes, the first telemetry received from the surface of
another planet.* [118]
CHAPTER 7. VENUS
separate missions.* [124] The Pioneer Venus Orbiter was
inserted into an elliptical orbit around Venus on 4 December 1978, and remained there for over 13 years, studying the atmosphere and mapping the surface with radar.
The Pioneer Venus Multiprobe released a total of four
probes, which entered the atmosphere on 9 December
1978, returning data on its composition, winds and heat
fluxes.* [125]
180-degree panorama of the Venusian surface from the Soviet
Venera 9 lander
The Venera program continued with Venera 8 sending
data from the surface for 50 minutes, after entering the
atmosphere on 22 July 1972. Venera 9, which entered the
atmosphere of Venus on 22 October 1975, and Venera
10, which entered the atmosphere three days later, sent
the first images of the Venusian landscape. The two landing sites presented different terrains in the immediate
vicinities of the landers: Venera 9 had landed on a 20degree slope scattered with boulders around 30–40 cm
across; Venera 10 showed basalt-like rock slabs interspersed with weathered material.* [122]
The Pioneer Venus orbiter
In the meantime, the United States had sent the Mariner
10 probe on a gravitational slingshot trajectory past Venus
on its way to Mercury. On 5 February 1974, Mariner 10
passed within 5790 km of Venus, returning over 4000
photographs as it did so. The images, the best then
achieved, showed the planet to be almost featureless in
visible light, but ultraviolet light revealed details in the
clouds that had never been seen in Earth-bound observations.* [123]
The American Pioneer Venus project consisted of two
Position of Venera landing sites returning images form the surface
Four more Venera lander missions took place over the
next four years, with Venera 11 and Venera 12 detecting Venusian electrical storms;* [126] and Venera 13 and
Venera 14, landing on 1 and 5 March 1982, returning
the first colour photographs of the surface. All four missions deployed parachutes for braking in the upper atmosphere, then released them at altitudes of 50 km, the
dense lower atmosphere providing enough friction to allow for unaided soft landings. Both Venera 13 and 14
analysed soil samples with an on-board X-ray fluorescence spectrometer, and attempted to measure the compressibility of the soil with an impact probe.* [126] Venera 14 struck its own ejected camera lens cap and its
probe failed to contact the soil.* [126] The Venera program came to a close in October 1983, when Venera 15
and Venera 16 were placed in orbit to conduct mapping of
the Venusian terrain with synthetic aperture radar.* [127]
In 1985, the Soviet Union took advantage of the opportunity to combine missions to Venus and Comet Halley,
which passed through the inner Solar System that year.
En route to Halley, on 11 and 15 June 1985, the two
spacecraft of the Vega program each dropped a Venerastyle probe (of which Vega 1's partially failed) and released a balloon-supported aerobot into the upper atmosphere. The balloons achieved an equilibrium altitude of
around 53 km, where pressure and temperature are comparable to those at Earth's surface. They remained operational for around 46 hours, and discovered the Venusian atmosphere was more turbulent than previously believed, and subject to high winds and powerful convection
cells.* [128]* [129]
7.5. EXPLORATION
7.5.4
Radar mapping
107
their respective missions to the outer planets, but Magellan was the last dedicated mission to Venus for over a
decade.* [132]* [133]
7.5.5 Current and future missions
NASA's MESSENGER mission to Mercury performed
two fly-bys of Venus in October 2006 and June 2007, to
slow its trajectory for an eventual orbital insertion of Mercury in March 2011. It collected scientific data on Venus
during both fly-bys.* [134]
Magellan radar topographical map of Venus (false colour)
The Venus Express probe was designed and built by
the European Space Agency. Launched on 9 November 2005 by a Russian Soyuz-Fregat rocket procured
through Starsem, it successfully assumed a polar orbit
around Venus on 11 April 2006.* [135] The probe is undertaking a detailed study of the Venusian atmosphere
and clouds, including mapping of the planet's plasma environment and surface characteristics, particularly temperatures. One of the first results from Venus Express is
the discovery that a huge double atmospheric vortex exists at the southern pole.* [135]
Artist's impression of a Stirling cooled Venus Rover.* [136]
Five global views of Venus by Magellan.
Early Earth-based radar provided a basic idea of the surface. The Pioneer Venus and the Veneras provided improved resolution.
The United States' Magellan probe was launched on 4
May 1989, with a mission to map the surface of Venus
with radar.* [26] The high-resolution images it obtained
during its 4½ years of operation far surpassed all prior
maps and were comparable to visible-light photographs
of other planets. Magellan imaged over 98% of the
Venusian surface by radar,* [130] and mapped 95% of its
gravity field. In 1994, at the end of its mission, Magellan was sent to its destruction into the atmosphere of
Venus to quantify its density.* [131] Venus was observed
by the Galileo and Cassini spacecraft during fly-bys on
The Japan Aerospace Exploration Agency (JAXA) devised a Venus orbiter, Akatsuki (formerly“Planet-C”),
which was launched on 20 May 2010, but the craft failed
to enter orbit in December 2010. Hopes remain that the
probe can successfully hibernate and make another insertion attempt in six years. Planned investigations included surface imaging with an infrared camera and experiments designed to confirm the presence of lightning,
as well as the determination of the existence of current
surface volcanism.* [137]
The European Space Agency (ESA) hopes to launch a
mission to Mercury in 2016, called BepiColombo, which
will perform two fly-bys of Venus before it reaches Mercury orbit in 2020.* [138]* [139]
NASA will launch the Solar Probe Plus in 2018, which
will perform seven Venus fly-bys during its six-year, 24orbit reconnaissance of the Sun.* [140]
Under its New Frontiers Program, NASA has proposed a
108
CHAPTER 7. VENUS
lander mission called the Venus In-Situ Explorer to land
on Venus to study surface conditions and investigate the
elemental and mineralogical features of the regolith. The
probe would be equipped with a core sampler to drill into
the surface and study pristine rock samples not weathered by the harsh surface conditions. A Venus atmospheric and surface probe mission, “Surface and Atmosphere Geochemical Explorer”(SAGE), was selected by
NASA as a candidate mission study in the 2009 New
Frontiers selection,* [141] but the mission was not selected for flight.
sample return by slowing down and entering then returning, and a surface sample return.* [145]
7.5.8 Spacecraft timeline
This is a list of attempted and successful spacecraft that
have left Earth to explore Venus more closely.* [146]
Venus has also been imaged by the Hubble Space Telescope in Earth orbit, and distant telescopic observations
are another source of information about Venus.
Venera-D is a possible Russian mission in the
2020s* [148]
7.6 In culture
See also Venus (mythology), Venus (astrology) and
Historical observations and impact
Venus aircraft concept
The Venera-D (Russian: Венера-Д) probe is a proposed
Russian space probe to Venus, to be launched around
2016, to make remote-sensing observations around the
planet and deploying a lander, based on the Venera design, capable of surviving for a long duration on the surface. Other proposed Venus exploration concepts include
rovers, balloons, and aeroplanes.* [142]
Throughout history and cultures, the planet has been of
remarkable importance as an especial object of observation, reflection and projection. Popular beliefs and observations resulted in different and in parts similar patterns
in mythology as well as phenomenological descriptions,
attributions and depictions, e.g. in astrology. Such developments in manifestations of human thought reflect the
planet's image as a result of early observations of Venus
and their impact on culture and science.
In late 2013 the Venus Spectral Rocket Experiment took 7.6.1 Etymology
place, which launched a sub-orbital space telescope.
The adjective Venusian is commonly used for items related to Venus, though the Latin adjective is the rarely
7.5.6 Manned fly-by concept
used Venerean; the archaic Cytherean is still occasionally encountered. Venus is the only planet in the Solar
Main article: Manned Venus Flyby
System that is named after a female figure.* [lower-alpha
1] (Three dwarf planets —Ceres, Eris and Haumea —
*
A manned Venus fly-by mission, using Apollo program along with many of the first discovered asteroids [149]
hardware, was proposed in the late 1960s.* [143] The and some moons (such as the Galilean moons) also have
mission was planned to launch in late October or early feminine names. Earth and the Moon also have feminine
November 1973, and would have used a Saturn V to send names in many languages—Gaia/Terra, Selene/Luna—
three men to fly past Venus in a flight lasting approxi- but the female mythological figures who personified* them
mately one year. The spacecraft would have passed ap- were named after them, not the other way around.) [150]
proximately 5,000 km (3,100 mi) from the surface of
Venus about four months later.* [143] Inspiration Mars includes a manned Venus flyby in their 2021 mission.* [144] 7.6.2
Venus symbol
Main article: Venus symbol
The astronomical symbol for Venus is the same as that
used in biology for the female sex: a circle with a small
Various concepts for a Venus sample return include a cross beneath.* [151] The Venus symbol also represents
high-speed upper atmosphere collection, an atmosphere femininity, and in Western alchemy stood for the metal
7.5.7
Sample return
7.8. SEE ALSO
109
and oxygen) would be a lifting gas in the Venusian atmosphere of mostly carbon dioxide. This has led to
proposals for “floating cities”in the Venusian atmosphere.* [152] Aerostats (lighter-than-air balloons) could
be used for initial exploration and ultimately for permanent settlements.* [152] Among the many engineering
challenges are the dangerous amounts of sulfuric acid at
these heights.* [152]
7.8 See also
• Aspects of Venus
• Mariner 10 Space probe to Venus
• 2001 CK32
• 2002 VE68
• 2012 XE133
copper.* [151] Polished copper has been used for mirrors from antiquity, and the symbol for Venus has sometimes been understood to stand for the mirror of the goddess.* [151]
• Geodynamics of Venus
• Geology of Venus
• Observations and explorations of Venus
• Venus zone
7.7 Colonization and terraforming
Main articles: Colonization of Venus and Terraforming
of Venus
Owing to its extremely hostile conditions, a surface
7.9 Notes
[1] Goddesses such as Gaia and Terra were named after Earth,
and not vice versa.
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(
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• Detailed information about transits of Venus
• Geody Venus, a search engine for surface features
• Maps of Venus in NASA World Wind
7.11. EXTERNAL LINKS
• Chasing Venus, Observing the Transits of Venus
Smithsonian Institution Libraries
• Venus Crater Database Lunar and Planetary Institute
• Calculate/show the current phase of Venus (U.S.
Naval Observatory)
• Venus Astronomy Cast episode No. 50, includes full
transcript.
• Thorsten Dambeck: The Blazing Hell Behind the
Veil, MaxPlanckResearch, 4/2009, p. 26–33
• Gray, Meghan (2009). “Venus”. Sixty Symbols.
Brady Haran for the University of Nottingham.
• Venus Exploration Themes – February 2014
7.11.1
Cartographic resources
• PDS Map-a-Planet & Venus Nomenclature
• Gazeteer of Planetary Nomenclature – Venus
(USGS)
• Map of Venus
• Movie of Venus at National Oceanic and Atmospheric Administration
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7.12 Text and image sources, contributors, and licenses
7.12.1
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Vystrix Nexoth, Azure Haights, BillCook, MPerel, Sam Korn, (aeropagitica), Krellis, Pharos, Hagerman, Supersexyspacemonkey, Phyzome, TobyRush, Jcrocker, Knucmo2, Jumbuck, Storm Rider, Danski14, Bob rulz, Qwe, Nik42, Mo0, Andrewpmk, AzaToth, Lightdarkness, RoySmith, Mlm42, Hu, Bart133, Snowolf, Wtmitchell, Dhartung, Schapel, Hadlock, Knowledge Seeker, Yuckfoo, Suruena, Evil
Monkey, Tony Sidaway, Amorymeltzer, Alfvaen, Sciurinæ, Inge-Lyubov, LFaraone, Gortu, Gene Nygaard, Paraphelion, Ringbang, HenryLi, Kitch, Dan100, Antifamilymang, Harvestdancer, Adrian.benko, Oleg Alexandrov, Tariqabjotu, Zephiris, Feezo, Siafu, Kfitzner,
WilliamKF, Novacatz, Haverton, Bacteria, Richard Arthur Norton (1958- ), Sanjaymjoshi, Rorschach, OwenX, Woohookitty, TigerShark, PoccilScript, Daniel Case, Ugo, Uncle G, Borb, HisHighness420, TomTheHand, BillC, Benbest, Pol098, Bricktop, Kristaga, Duncan.france, MONGO, Mpatel, Gayle crockett, Pi@k, Will.i.am, Thesquire, Bluemoose, Wtfunkymonkey, Sengkang, GregorB, Eyreland,
Waldir, Wayward, とある白い猫, Alec Connors, Smartech, Wisq, Gavino, Aarghdvaark, Ashmoo, Graham87, Marskell, Magister Mathematicae, MC MasterChef, FreplySpang, Hrothgar15, Nlsanand, Pentawing, Search4Lancer, Canderson7, Drbogdan, Sjakkalle, Rjwilmsi,
Tim!, Koavf, Panoptical, Commander, Urbane Legend, Bob A, Bill37212, Stardust8212, Captmondo, Tawker, Mike s, SMC, Mike Peel,
Justin Hirsh, Kazrak, Crazynas, Ligulem, SeanMack, Bubba73, Brighterorange, Yug, The wub, Bhadani, GregAsche, Sango123, Lotu,
Yamamoto Ichiro, FayssalF, Titoxd, Nikson-t, SchuminWeb, RobertG, Old Moonraker, Flydpnkrtn, Musical Linguist, Nihiltres, Harmil,
GT, RexNL, Gurch, RobyWayne, Vayne, Arctic.gnome, DannyZ, Str1977, TeaDrinker, Consumed Crustacean, Supersaiyanplough, Srleffler, Le Anh-Huy, Imnotminkus, King of Hearts, Urzeitlich, Chobot, Spasemunki, Digitalme, Gwernol, Algebraist, Thumbtacks, Diogenes00, YurikBot, Wavelength, TexasAndroid, Spacepotato, Vedranf, Reverendgraham, Neitherday, Sceptre, Hairy Dude, Deeptrivia,
Huw Powell, Jimp, Gene.arboit, Kymacpherson, RussBot, Sarranduin, Sillybilly, TheDoober, Splash, SpuriousQ, Fabricationary, Zelmerszoetrop, Stephenb, Lavenderbunny, Matt.lohkamp, Wimt, NawlinWiki, Jessesaurus, Wiki alf, BGManofID, Aeusoes1, Test-tools, Jaxl,
Agent003, Terfili, Journalist, Stephen e nelson, Dureo, Bmdavll, Cleared as filed, Irishguy, Anetode, Brandon, Cholmes75, CPColin,
Chal7ds, Rmky87, Moe Epsilon, Tony1, Alex43223, Harishsubramanian, The Peacemaker, Syrthiss, Bota47, Jessemerriman, Hosterweis,
Tachyon01, Milkyeyes, Brisvegas, Martinwilke1980, Yasth, Dna-webmaster, Nick123, Wknight94, Ms2ger, Robost, FF2010, 21655, Keystone32, PTSE, Chesnok, Kandrey89, Ageekgal, Pb30, Canley, BorgQueen, Petri Krohn, Alias Flood, AliasHandler, Peter, Hurricane
Devon, Jolb, HereToHelp, Emc2, ArielGold, Calilasseia, Junglecat, Banus, RG2, KNHaw, Iago Dali, Draicone, Serendipodous, DVD
R W, Brentt, Caponer, The Wookieepedian, Deuar, Sardanaphalus, Attilios, KnightRider, Jas pierce, A bit iffy, SmackBot, Aths, ZorkFox, Doktor, KnowledgeOfSelf, Martin.Budden, Lagalag, Primetime, Jim62sch, Vald, Bwilliams, Jagged 85, Davewild, ScaldingHotSoup, Verne Equinox, MarcusPan, Jedikaiti, EncycloPetey, Kintetsubuffalo, Edgar181, Galloglass, Markeer, Gaff, Xaosflux, Pinpoint23,
Cuddlyopedia, Aksi great, Peter Isotalo, Hmains, Skizzik, ERcheck, JAn Dudík, Tv316, Saros136, Amatulic, Chris the speller, Endroit,
Bluebot, Ciacchi, Cush, Derrickjohnson2, Vandago, Keegan, Persian Poet Gal, Oli Filth, Jon513, Pylori, Anchoress, MalafayaBot, Hibernian, WeniWidiWiki, Ikiroid, Ctbolt, Ned Scott, Roy Al Blue, Sbharris, Colonies Chris, Gracenotes, Mikker, Gyrobo, Spride, Zsinj,
E946, Can't sleep, clown will eat me, Ajaxkroon, Aerobird, Tamfang, V1adis1av, Mrwuggs, The Placebo Effect, Racklever, OOODDD,
NLightmare, Astrobhadauria, Darthgriz98, Wikipedia brown, Chiao, Arod14, Pnkrockr, Aces lead, Addshore, Edivorce, Celarnor, Ctifumdope, Notovny, Wince01, Flyguy649, Iapetus, Hopquick, Nakon, Ninjers, Blake-, SnappingTurtle, RandomP, Alexander110, Mini-Geek,
Mikaly, Weregerbil, Polonium, Only, Hammer1980, Glenn Browne, Zonk43, BiggKwell, Ericl, Oceanh, Kalathalan, Mystaker1, Ligulembot, DDima, Vina-iwbot, Samuel Sol, Bejnar, Pilotguy, Kukini, Sarfa, Tredanse, SashatoBot, Nathanael Bar-Aur L., Esrever, Erimus,
Harryboyles, Rklawton, Kuru, Richard L. Peterson, John, Twohlrab3, AmiDaniel, WhiteCat, Scientizzle, Vgy7ujm, Ascend, Heimstern,
Caylan12-06, Soumyasch, Breno, Linnell, Kreuzfeld, JorisvS, Temple, Evan Robidoux, GVP Webmaster, Mgiganteus1, Aleenf1, IronGargoyle, Jess Mars, Ckatz, The Man in Question, RandomCritic, Il consiglieri, A. Parrot, Werdan7, Noah Salzman, Suraj vas, Xiaphias,
Rwboa22, Cajolingwilhelm, Waggers, SandyGeorgia, Anonymous anonymous, Ryulong, Ephant, Big Smooth, RichardF, Elb2000, Jose77,
NuncAutNunquam, Politepunk, Sonic3KMaster, Michaelbusch, Masoninman, LeyteWolfer, Joseph Solis in Australia, Newone, Pegasus1138, Pokemega32, GDallimore, Fsotrain09, Espi, Abdul Muhib, Thomasph, Civil Engineer III, Peteweez, Tawkerbot2, Dlohcierekim,
Daniel5127, Ouishoebean, Acom, Pete g1, Poolkris, Orangutan, Samnuva, MightyWarrior, Cavac, JForget, InvisibleK, CmdrObot, Deon,
Ale jrb, Wafulz, Scohoust, Funion987, Picaroon, S035593, Zureks, CWY2190, Ruslik0, GHe, Benwildeboer, DeepSkyFrontier, Dgw,
Dr. Eggman3, SEJohnston, Skoch3, Lazulilasher, Logical2u, Avillia, Casper2k3, Ken Gallager, Charlie Huggard, Ufviper, Icek, Sopoforic, Cydebot, Nbound, Jjeffrey, ChristTrekker, Reywas92, Treybien, Steel, SyntaxError55, Sruav, Gogo Dodo, Tom.freeman, Anthonyhcole, Flowerpotman, Fredo1983, ST47, Dark-hooded smoker, Scott14, Fifo, Michael C Price, Tawkerbot4, DumbBOT, Inkington, After Midnight, Omicronpersei8, Robert.Allen, Daniel Olsen, Gimmetrow, FrancoGG, EnglishEfternamn, Rjm656s, TiroDeAethra,
DJBullfish, Thijs!bot, Epbr123, Oreo man, Mikebuer, Opabinia regalis, Factmon, Hit bull, win steak, LeeG, Aster2, RolfSander, Keraunos, 24fan24, Headbomb, Wongizzle06, John254, Tapir Terrific, Bad Astronomer, Neil916, I do not exist, Ctu2485, Astrobiologist,
7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES
117
Lars Lindberg Christensen, Davidhorman, Pahoeho, GregMinton, Prof info, Lithpiperpilot, BlytheG, Escarbot, KrakatoaKatie, AntiVandalBot, Majorly, Abu-Fool Danyal ibn Amir al-Makhiri, Luna Santin, Crabula, Opelio, EarthPerson, Benjaburns, Quintote, Autocracy,
17Drew, Jj137, Zappernapper, Dr. Submillimeter, Gdo01, Gregorof, Once in a Blue Moon, SkoreKeep, Fireice, Storkk, Myanw, Kaini,
Nicodème, PresN, Joehall45, Zombiepirate 13, IrishFBall32, JAnDbot, Narssarssuaq, Jirachi, Milonica, Deflective, MER-C, ElComandanteChe, CosineKitty, Something14, IanOsgood, Bigscarymike, Andonic, Noobeditor, Hut 8.5, 100110100, Tstrobaugh, Hardee67, Kirrages,
Rothorpe, .anacondabot, Acroterion, FaerieInGrey, Ruthfulbarbarity, WolfmanSF, Murgh, Parsecboy, Bongwarrior, VoABot II, MiguelMunoz, MartinDK, Smoke., Transcendence, Xn4, Lubumbashi, Hasek is the best, SYLFan74, -Kerplunk-, CattleGirl, Mbc362, Xkcd,
Selfishjeans, ‫باسم‬, Bigdan201, Violentbob, Rami R, Jespinos, Confiteordeo, BillDeanCarter, Jim Douglas, Nyttend, Rich257, Kukanotas, Cyktsui, Ttpedia, BatteryIncluded, ArthurWeasley, Notamisfit, Adrian J. Hunter, Hamiltonstone, Allstarecho, Involutaryhaxor, Linday51, P.B. Pilhet, Jc1346729, Spellmaster, Shijualex, Dmehring, Glen, DerHexer, Wdflake, Megalodon99, Khalid Mahmood, Kheider,
Darkside5001, NatureA16, Gjd001, B9 hummingbird hovering, Hdt83, MartinBot, BetBot, Arjun01, Poeloq, Eshafto, Rettetast, Mschel,
Pallasathena, CommonsDelinker, AlexiusHoratius, Bryanadamtan, WelshMatt, Lilac Soul, Nerablade, Omega34, Exarion, Huzzlet the bot,
Watch37264, Leon math, DrKiernan, Trusilver, GreenRunner0, Rgoodermote, EscapingLife, AAA!, Ali, JamesR, Sp3000, Lizrael, Abby,
Hans Dunkelberg, Nigholith, Teacher123, Eliz81, Extransit, Tdadamemd, OfficeGirl, KatyNicholslikesnosehair, Gzkn, Zipzipzip, FrummerThanThou, Gman124, Lunokhod, Jackj08, Jeepday, Oddgunner, Gurchzilla, Squidlegs number one, Pyrospirit, Ravenicus451, Chemicalrubber, NewEnglandYankee, Sd31415, SmilesALot, Milchild05, SJP, IsaacMcHelicopter, W3stfa11, Tanaats, Shoessss, Cbddoughboy, Sunderland06, Cometstyles, Craiglynn666, U.S.A.U.S.A.U.S.A., C.m.jones, Aramjm, Elenseel, Yomama 007, Homo logos, Bianca
w123, Jcamts, Rvwedd, Piepoop, Sgeureka, Xiahou, Angel123123, ThePointblank, Kelevra88, Erasmosis, Spellcast, Idarin, Maridius,
Guy14, Fainites, Jochem Atteveld, Lights, Deor, King Lopez, VolkovBot, CWii, Midoriko, Jlaramee, Tesscass, Alexandria, AlnoktaBOT,
Toddles29, Katydidit, Dextrose, Philip Trueman, Law Lord, TXiKiBoT, Quackdave, Dwmr, Ezer22, Rightfully in First Place, Differo,
Reptile5000, Secret agent with brown hat, Wedge1, Qaletaqa, Caster23, GDonato, Dchall1, Jorgezoltan, Sean D Martin, DJFrankie2468,
Qxz, Lradrama, Corvus cornix, MasterSci, Phoxtrot, Danlikebooks, 06monkey, JhsBot, Don4of4, Cool moe dee 345, Mkolp58, Broadbot, Abdullais4u, Fbs. 13, Seb az86556, Mannafredo, UnitedStatesian, Myden, Cremepuff222, Xyragx, Onore Baka Sama, Moppt,
Trueemo, CarbonUnit2, Conalmal, CO, RR1991, NateLevine, Dark Wolf101, SwahilidR, Arfur20, SheffieldSteel, Pious7, Billinghurst,
Ar-wiki, Brainmuncher, Alecdude, Viktor-viking, Synthebot, Shrinkbcoz, Rbinet, Benandersen, Burntsauce, Songtag, Kedeja, Sampaultan,
Gspinoza, Brianga, Ricegator, Alcmaeonid, Hinomaru kun, Whalequeen, Smerlinare, Jordanjhd, AlleborgoBot, Drseal, Srogue, Herojoe1000, Charvez12, Vsst, NHRHS2010, EmxBot, Tedstryk, D. Recorder, Demmy, Jrod2, SieBot, Kfc1864, TJRC, Jim77742, PlanetStar,
Scarian, Oldag07, Gerakibot, Viskonsas, Caltas, Triwbe, Bladesonic, Jacob102193, Yulu, Purbo T, Eaomatrix, Keilana, Lonewolf1654,
Interchange88, Aaaxlp, Aillema, Jonathan Barrett, Jakeis1, Radon210, Oysterguitarist, Editore99, Oda Mari, Chris Gottschalk, I need a
stupid username, Gublefink, Dangerousnerd, Paolo.dL, JSpung, Wombatcat, Jakmak123, Calex1, Mackojee, Tenjhotenge, Oxymoron83,
Ddxc, Smilesfozwood, Conner40, Lukelpv5853, Mattl2001, Nk.sheridan, Gangsterls, KPH2293, Nerd123456789, Asdarknessfadesaway,
You blocked me, Steven Zhang, Lightmouse, Ehousehay, ThAtSo, AustinTarzia, Murlough23, RSStockdale, Lopp777, BenoniBot, Dtbrock,
Scott55555, Dsmith7707, Laddog, I'm a sockpuppet, Ttime27, SOLOMON92, Sertafied, Paddywikman, Dermot92, Vandalismhater789,
Nagolkid2, Poopmaster01, Poopmaster03, ChrisWallis, Slavkovranes29, Barks0, Maelgwnbot, FtLulz, LonelyMarble, Anchor Link Bot,
Jons63, Into The Fray, AndySmith84, C0nanPayne, Uscchic735, Freewayguy, Athenean, Jdmmxbth, SallyForth123, Sagredo, Loren.wilton,
ClueBot, Mariordo, PipepBot, Matdrodes, Postmortemjapan, Starkiller88, Wercloud, Jan1nad, T.Neo, UserDoe, Cp111, Bobisbob, Misbah Ismailjee, Aria1561, Stargazer 7000, SuperHamster, Wikidog783, Ajczdabomb, I am the antichrist, Donthackppl, Iminnocent0,
Danie2dixon, Neverquick, Knezzoran, DigitalAttorney, DragonBot, Ale221, Excirial, -Midorihana-, M4gnum0n, Breakdancingninja, War
guy234, Monobi, PixelBot, Deathgiggity, Supabanakid, Thispagedoesown, Darthnat, Commdor, Sun Creator, P-griffin150, Rideauposse,
JINN66, Ice Cold Beer, Cenarium, Aurora2698, PhySusie, Blitz123, Poisonink, Mtsmallwood, Dekisugi, Sophixer, Cyclopaedia, BOTarate,
Kakofonous, TomJMcDonald, Aprock, Sparta300xps, CowAteMe, Thingg, Aitias, TR 667, R98563256, Superericmoore, Xplayabyname,
Varha, Qwfp, Tylerdfreeze11, Isidoros47, Nickman339, Must eat worms, Chr334, BodhisattvaBot, Swift as an Eagle, Snorks1234, Mattrave, Demonminde, Jupiter Rapist, Rreagan007, Poodudeman, Thetruth77, Eiaschool, Ericcool99, Yoshi thomas, Veenluk, Noctibus,
NHJG, JinJian, Qwertyuiop click, Dinosaursrule42, Junox, JCDenton2052, Kurtus77, Homrsmpsnrulz, Miagirljmw14, GiLLyDaGuN,
Jadtnr1, Apocalypse2011, Kbdankbot, Sis143, Angrome9, Ryan-McCulloch, Hawkania, Roentgenium111, Lagus970, DOI bot, Element16, Fgnievinski, Bugmenot1984, Punkprincess082307, Savage84, DrSamba, Heremod, Proxima Centauri, LaaknorBot, CarsracBot,
Favonian, ChenzwBot, LinkFA-Bot, Xev lexx, R.H.H.L.B., 84user, Numbo3-bot, F Notebook, Craigsjones, Lightbot, Ettrig, Windward1,
Koltentb, Yobot, Ptbotgourou, Mech Aaron, TaBOT-zerem, Castagna, KamikazeBot, Рөстәм Нурыев, Ayrton Prost, The Flying Spaghetti
Monster, AnomieBOT, Archon 2488, Galoubet, Materialscientist, Ckruschke, The High Fin Sperm Whale, Citation bot, Nunna003, Xqbot,
Timir2, Intelati, A455bcd9, TechBot, Lionboy-Renae, Smk65536, Gospodar svemira, Mlpearc, Srich32977, Woodstock aeb, Nayvik, HernanQB, RibotBOT, Charvest, Shadowjams, Datakid1100, Confront, Fotaun, Armchairslugger, Thehelpfulbot, FrescoBot, Dogzrule101,
LucienBOT, Paine Ellsworth, Tobby72, Io Herodotus, Lookang, Drongou, KokkaShinto, Craig Pemberton, Dhtwiki, Ivoras, Citation bot
1, DigbyDalton, Kalisitahi, Wiklol, Pinethicket, HRoestBot, Tanweer Morshed, Tom.Reding, RedBot, Lars Washington, Thinking of England, Pink fuzzy slippers, Djwebb1969, VAP+VYK, FoxBot, Double sharp, TobeBot, Sweet xx, DixonDBot, Vrenator, Begoon, Luvenno,
Tbhotch, RjwilmsiBot, Ripchip Bot, Elitropia, DASHBot, EmausBot, WikitanvirBot, Qurq, AmericanLeMans, Racerx11, Gwillhickers,
HarDNox, Kkkdddiii, ZéroBot, Josve05a, A2soup, Nicolas Eynaud, AvicAWB, Hevron1998, Aeonx, Demomoer, Cline92, Мл.научный
сотрудник, L Kensington, Andy 3015, Sailsbystars, Ontyx, Grv619, StephenKingFan100, K Alan Drummond, ChuispastonBot, Knochen,
ChiZeroOne, Terra Novus, ThomasElwood, Karthikrrd, Mjbmrbot, Fjörgynn, ClueBot NG, Xession, Kamek98, Lanthanum-138, Frietjes, Dalekcan, Pollying, Pluma, Megalobingosaurus, Diyar se, Bibcode Bot, Supergamer101, RZuljani, BG19bot, Pine, WikiPeterD,
MKar, Hz.tiang, Odarcan, AvocatoBot, ERJANIK, Cadiomals, Mdy66, PrintedScholar, Harizotoh9, Tycho Magnetic Anomaly-1, Zedshort,
Ubiquinoid, Nbrothers, Oscar45596524, BattyBot, ChrisGualtieri, Asisman, Waylesange, Dexbot, RazrRekr201, Blobbie244, Anderson,
Reatlas, Joeinwiki, Anastronomer, Lindenhurst Liberty, Seppi333, Kogge, AfadsBad, Artificial123, Samatict, Exoplanetaryscience, Cancina5645, Ethically Yours, Monkbot, Koolman642, Spiderjerky, Py1905py, Tetra quark, Anand2202, TheWhistleGag and Anonymous:
1610
• Mars Source: http://en.wikipedia.org/wiki/Mars?oldid=656088329 Contributors: Joao, Peter Winnberg, Dreamyshade, Lee Daniel
Crocker, Brion VIBBER, Eloquence, Mav, Bryan Derksen, Robert Merkel, Zundark, Berek, Tarquin, Stephen Gilbert, Jeronimo, -- April,
Dave McKee, Ed Poor, Mirwin, Eob, Danny, XJaM, JeLuF, Rmhermen, Christian List, MadSurgeon, Miguel, Roadrunner, SimonP, Zoe,
Waveguy, Arj, Arno, Hephaestos, Olivier, Xlation, Mbecker, Fransvannes, Spiff, Edward, Patrick, D, Michael Hardy, Oliver Pereira, Lexor,
David Martland, Gabbe, Ixfd64, Sannse, Cameron Dewe, Shoaler, GTBacchus, Minesweeper, Egil, Looxix, Ihcoyc, Ahoerstemeier, Anders Feder, Stevenj, William M. Connolley, Zouhair, Plop, Notheruser, Mark Foskey, Setu, Александър, Salsa Shark, Cyan, Poor Yorick,
Netsnipe, Susurrus, Kwekubo, Rotem Dan, Evercat, Astudent, Ghewgill, Samuel, BRG, Epo, Schneelocke, Iseeaboar, Hike395, RodC,
Adam Bishop, Vanished user 5zariu3jisj0j4irj, Timwi, JonMoore, Wikiborg, RickK, Reddi, Stone, Denni, Audin, Doradus, Haukurth, Birkett, Tpbradbury, Dragons flight, Morwen, Populus, Omegatron, Ed g2s, Rnbc, Babbler, Samsara, Thue, Xaven, Traroth, Nickshanks,
118
CHAPTER 7. VENUS
Sandman, Bloodshedder, Scott Sanchez, Lmov, Skood, Wetman, Chrisjj, Secretlondon, Jerzy, Flockmeal, Liam, Jni, Twang, Donarreiskoffer, Branddobbe, MattSal, Robbot, Zandperl, Alrasheedan, Baldhur, Nurg, Romanm, Naddy, Mikepelley, PedroPVZ, Rursus, TMLutas, Mlaine, Roscoe x, Halibutt, Caknuck, Bkell, Hadal, UtherSRG, Borislav, Vikingstad, Anthony, SoLando, BovineBeast, Robert
Happelberg, ShutterBugTrekker, Nephelin, Alexwcovington, Centrx, Giftlite, Reubenbarton, DocWatson42, MPF, Marnanel, Djinn112,
Awolf002, Jyril, Laudaka, YanA, Sj, TOttenville8, Yuri koval, Harp, Wolfkeeper, Ævar Arnfjörð Bjarmason, Levin, Lupin, Ferkelparade, Rbs, Herbee, Angmering, 0x6D667061, Braaropolis, Bradeos Graphon, Wwoods, Anton Mravcek, Everyking, Perl, Curps, Jonathan
O'Donnell, Michael Devore, Henry Flower, Wikibob, Joe Kress, Cantus, Semorrison, Revth, Erdal Ronahi, Guanaco, Beowulf king,
Mboverload, Darin, Matt Crypto, Python eggs, Bobblewik, Mateuszica, John Abbe, Wmahan, OldakQuill, Stevietheman, ChicXulub,
Chowbok, JeffyJeffyMan2004, Latitudinarian, Kums, Pcarbonn, Ran, Antandrus, The Singing Badger, HorsePunchKid, Beland, Eroica,
MisfitToys, Piotrus, Scottperry, Vanished user 1234567890, Kaldari, Nils, Josquius, Rdsmith4, Oneiros, Kesac, Wikster E, Latitude0116,
Kevin B12, Tomruen, CharlieZeb, Kuralyov, Icairns, Gscshoyru, Nickptar, B.d.mills, Bradlegar, Neutrality, Urhixidur, Edsanville, TJSwoboda, Jafro, Ukexpat, Klemen Kocjancic, Trilobite, Tonik, M1ss1ontomars2k4, Adashiel, Lacrimosus, MaikSchreiber, Mike Rosoft,
Mr Bound, N328KF, Poccil, DanielCD, JTN, Ultratomio, Dablaze, Simmie, Jkl, Discospinster, Solitude, Rich Farmbrough, Guanabot,
GrantHenninger, Rameses, Vsmith, Edibobb, Florian Blaschke, MeltBanana, Ponder, Ibagli, Mani1, MuDavid, Aardark, Paul August,
Robertbowerman, SpookyMulder, Bg, Bender235, ESkog, NeilTarrant, Calamarain, Wild Bill, Kbh3rd, Neko-chan, Evice, Brian0918,
Mattingly23, RJHall, JamesR1701E, CanisRufus, Omnibus, JustPhil, MBisanz, El C, Huntster, Kwamikagami, Gnomz007, Worldtraveller, Aude, Shanes, Joaopais, Tom, Art LaPella, RoyBoy, Nickj, Mark R Johnson, Femto, Wareh, Dalf, Causa sui, Noren, Bobo192,
NetBot, Apollo2011, Olve Utne, Viriditas, AllyUnion, Phidauex, Mpvdm, Jojit fb, Pierre2012, Nk, ‫לערי ריינהארט‬, TheProject, Scentoni, Kpbtm, Vorlon, MPerel, Sam Korn, Gsklee, Shikasta, Perceval, HasharBot, Jumbuck, Stephen G. Brown, Bob rulz, Lyle, Junior
aspirin, Eleland, Keenan Pepper, Andrewpmk, Plumbago, Andrew Gray, A.T.M.Schipperijn, Riana, Yamla, Lectonar, MarkGallagher,
Scarecroe, Lightdarkness, RoySmith, TommyBoy, Mlm42, Hu, Malo, VladimirKorablin, Bart133, Metron4, Snowolf, BanyanTree, Mmbaldwin, KingTT, Suruena, Katepaull, Evil Monkey, Aaarrrggh, Tedp, Amorymeltzer, Sciurinæ, IMeowbot, Inge-Lyubov, Cmapm, Kusma,
Ianblair23, Itsmine, Paolorausch, Gene Nygaard, Alai, Iustinus, Avram Fawcett, Kazvorpal, Kitch, Ceyockey, BerserkerBen, RyanGerbil10,
Tariqabjotu, Siafu, Gmaxwell, Newnoise, WilliamKF, Plateau99, Bacteria, Kelly Martin, Woohookitty, Lost.goblin, Masterjamie, LOL,
Asteron, PoccilScript, Volcanopele, Uncle G, Benhocking, HisHighness420, BillC, Jacobolus, Matey, Bigfrozenhead, Benbest, Ikescs, Ma
Baker, Pol098, ^demon, JeremyA, Kristaga, MONGO, Xaliqen, Bamf, Pi@k, Astrophil, Sengkang, Someone42, GregorB, BlaiseFEgan,
Eyreland, Mb1000, CharlesC, Wayward, DanHobley, Teemu Leisti, Lazareth, Giantsrule, Gerbrant, Emerson7, Forezt, Ashmoo, Graham87, Marskell, WBardwin, Magister Mathematicae, BD2412, Li-sung, FreplySpang, JIP, Seyon, MasterPlan, AnimAlu, Pentawing,
Phasmatis, Drbogdan, Sjakkalle, Rjwilmsi, Koavf, Саша Стефановић, Ittiz, Loginnow, Vary, Hjb26, Stardust8212, Bruce1ee, Captain
Disdain, Coyo, MZMcBride, Tawker, Mike s, SMC, Mike Peel, Nneonneo, Kazrak, Crazynas, Cww, Bubba73, Brighterorange, Bhadani,
Sango123, Dbigwood, Yamamoto Ichiro, Ghalas, Marsbound2024, FayssalF, RCBot, FlaBot, Figs, Ian Pitchford, RobertG, Black Sword,
Flydpnkrtn, Latka, Crazycomputers, JiFish, MacRusgail, SouthernNights, Chanting Fox, Itinerant1, Themanwithoutapast, RexNL, DavideAndrea, BjKa, Arctic.gnome, DannyZ, KFP, TeaDrinker, Carrionluggage, Goudzovski, Alphachimp, Srleffler, Johhny-turbo, Le Anh-Huy,
Gareth E Kegg, Bedford, Bschlee, MoRsE, Nomadtales, Chobot, Metropolitan90, Mordicai, Gwernol, Rollie, EamonnPKeane, Slasher600,
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Ydris, Nick, Wonglokking, Ghostreveries, Jimmyre, CecilWard, ThrashedParanoid, Blu Aardvark, E rulez, Dfgarcia, PhilipC, Number 57,
Moe Epsilon, Misza13, Grafikm fr, Semperf, Tony1, Kwnd, Gadget850, DeadEyeArrow, Bota47, Darkfred, Milkyeyes, Martinwilke1980,
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Mars, Pogsquog, Ckatz, Riverkarl, The Man in Question, RandomCritic, ZincOrbie, Loadmaster, Slakr, Stwalkerster, Tac2z, Laogeodritt,
Yvesnimmo, Suraj vas, Grandpafootsoldier, Samaster1991, KHAAAAAAAAAAN, Dicklyon, Funnybunny, Ryulong, Sijo Ripa, Gazjo,
RichardF, Elb2000, Jose77, Michael Dinolfo, NuncAutNunquam, Kvng, Akademy, Politepunk, Tawkerbot, DabMachine, Webb.phillips,
ILovePlankton, Iridescent, K, JMK, Jake1293, Michaelbusch, Shakedust, Dekaels, Polymerbringer, Paul venter, Lakers, Ktan, Joseph
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Stereorock, Marysunshine, Civil Engineer III, Courcelles, Nkayesmith, Sxicrisis, Eluchil404, Tawkerbot2, Aldo12xu, Serb4c, Alegoo92,
Dlohcierekim, Broberds, Daniel5127, Chetvorno, Poolkris, Altonbr, Firstmagnitude, Orangutan, Mr Woman, Fvasconcellos, Rondack,
JForget, GeneralIroh, Taskmaster99, Mapsax, Vaughan Pratt, InvisibleK, WCar1930, Zooman555, Tanthalas39, Ale jrb, Wafulz, Tuvas,
Crescentnebula, Aherunar, Woudloper, Kris Schnee, Drinibot, Ruslik0, GHe, N2e, Chmee2, WeggeBot, Moreschi, Itportal, Decadencecavy, Phædrus, Ispy1981, Trunks6, Zaraahmed100, Ufviper, TJDay, Lightblade, Danrok, Nbound, ChristTrekker, Reywas92, Chilambu,
Steel, PorciusXX, DrunkenSmurf, Gogo Dodo, Travelbird, Llort, M£, Torvik, Daniel J. Leivick, B, Tawkerbot4, Gvil, Chrislk02, InvaderZod, Optimist on the run, Salulljoica, Bungle, ErrantX, Omicronpersei8, Nicoisgreat111, Daniel Olsen, PsychoSmith, Tejas.B, Richhoncho,
Kirk Hilliard, ‫הסרפד‬, Casliber, Eubulide, Thijs!bot, Epbr123, Dbarnes99, Joshuagay, Coelacan, NeutralPoint, ChunkySoup, King Bee, Sal-
7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES
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Ereiyo, Spangs, MDB913, Dr. Submillimeter, Modernist, SkoreKeep, Kerdek, Qwerty Binary, Fearless Son, Wl219, Myanw, Willthepwn,
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Onore Baka Sama, Nintendo121, Fartstank1996, Maxexcloo, Maxim, Bryan.dollery, ShapedNoise, Mr.Kennedy1, Pious7, Hellcat fighter,
Tcmstr134, Norty512, Synthebot, Enviroboy, 11warnjames, Calypsos, Phantomdj, FKmailliW, Julian Herzog, WatermelonPotion, Insanity
Incarnate, Kid45laundry, Jobberone, Wiggstar69, TheN0ble2, Smerlinare, AlleborgoBot, Bob the Rabbid, FreyasCrystalizedAngels, LuigiManiac, Jim Furtado, Vsst, EmxBot, Tedstryk, Oniwanbashuu, D. Recorder, Wraithdart, Mandynoty, Redandproud1, Viggio, Mediumemu,
Justyb, Akira112, Lksadfajsl, Elisa Woods, SieBot, Ersatzaxiom, Dusti, I OWN I OWN I OWN, Jim77742, Tehtorptsol, PlanetStar, NonChalance, YonaBot, Spartan, Luboogers25, Oldag07, OlliffeObscurity, Legend, Buddyonline7, Parhamr, Caltas, Xymmax, Triwbe, Carapar999, Vanished User 8a9b4725f8376, Stewartmacarth, Til Eulenspiegel, Wiljaneni, Jerryobject, Purbo T, Keilana, Chuckchuckerson,
Maddiekate, Streetfoo212, Android Mouse, Aillema, RadicalOne, Radon210, Cbsteffen, Azzjiggla, Mirkoruckels, Drorion, Themulemonk,
Derajenator, Wikipedophilia, Happyfeet999, John dildo, Wikipedosucklol, JustAnotherGuy01, RedandProud2, Lookypoojky, Helloasd,
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Lightmouse, Tombomp, AMCKen, Radzewicz, Murlough23, Schnahoo, T42at102, Alex.muller, Triberocker, BenoniBot, OKBot, Bennish, Svick, Maelgwnbot, LonelyMarble, Hiei-Touya-icedemon, AghastAmok, JohnnyMrNinja, Oldey, AWESOME-Odude, Jacob.jose,
Sean.hoyland, Randomblue, Hamiltondaniel, Konomono33, Killerman1, Choptube, Ascidian, Statue2, Nash London, Florentino floro, Jesus the savior, Marsterritory, Pinkadelica, Gregs gunners, Supraboy001, Schuylar247, Escape Orbit, AndySmith84, C0nanPayne, Ayleuss,
Wjmummert, Starcluster, Lol0075, Glades2, Athenean, SallyForth123, MenoBot, Martarius, Marzziano, Friend mole, ClueBot, Avenged
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Filip.vidinovski, Suniti karunatillake, Neverquick, Lampofdoom, Phenylalanine, House13, Jlarvae, Gthy1, B2012ball21, FrancescoA, Excirial, Jonapello22, Jusdafax, Hargitai, Nerguy, PixelBot, Sun Creator, BaconBoy914, Fukiyow, NuclearWarfare, Sepeople, SO-intOyOuxX, Cenarium, Jotterbot, Jo Weber, Dustymars, Scog, Razorflame, SockPuppetForTomruen, Redthoreau, BOTarate, Stepheng3, John
Paul Parks, Thingg, Bagunceiro, ApostleJoe, Goat217, BetoCG, GrahamDo, Kubek15, Helzart, Claytopia3, TheLasso, Sethrasmussen121,
DumZiBoT, Thetreesonmars, Showbread89, Aaronbwsm, UltraCaution, Spotturtle, Bluhbluhbluh94, Sk8rbabii202, DrOxacropheles,
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Dahn10, Airplaneman, SugarPlumLove, Homrsmpsnrulz, Headasploder, Xerbox, Kbdankbot, Olyus, Notmage2, Maldek, Kasey12297,
Roentgenium111, Chihuahua22, Lagus970, DOI bot, Jojhutton, HannahCRichards, Wonkinson, EjsBot, SigmaTap, Ronhjones, Kbcfan, PC-Cat, Delfinis, CanadianLinuxUser, Leszek Jańczuk, Wælgæst wæfre, Dyadron, NjardarBot, Skyezx, Koolgirl560, LaaknorBot,
CarsracBot, RebaFan1996, Glass Sword, Debresser, Favonian, LinkFA-Bot, West.andrew.g, Ks 7508, Peti610botH, Renatokeshet, Freshgroundcoffee, 84user, Sanawon, Numbo3-bot, Ace45954, The mars 789, Tide rolls, Sumguynamedj, Gail, SexualFinger, Wikichangerman, DrKeirnan, Hugsnkisses1996, Nubar24, Margin1522, Luckas-bot, Yobot, Randomguy1234567890, Beerdola, LightingRod, Ninjalemming, II MusLiM HyBRiD II, KamikazeBot, Dmarquard, AnomieBOT, KingofGnG, Archon 2488, SwiftlyTilt, 1exec1, Dwayne,
JackieBot, Lwangaman, Brutchersp, Ivan2007, Materialscientist, Redranger141, RadioBroadcast, Citation bot, JohnFromPinckney, LilHelpa, Lqstuart, Obersachsebot, Xqbot, Link dude177, TinucherianBot II, Timir2, Intelati, Clydecoast, Drilnoth, Smk65536, Gilo1969,
Boltz6100, Oncedarkness, Toa Nidhiki05, Tyrol5, Mlpearc, Arsia Mons, Jimwilcox79, GrouchoBot, Maria Sieglinda von Nudeldorf, Zefr,
RibotBOT, Enceladusgeysers, Charvest, GhalyBot, Silbad, Samwb123, Fotaun, Zytroft, Diamondhead123, Celuici, DasallmächtigeJ, Green
Cardamom, Dave3457, Depictionimage, Lukepolick, FrescoBot, Surv1v4l1st, Originalwana, Kuliwil, Tobby72, Io Herodotus, Lookang,
KokkaShinto, Majopius, 培养皿, Kwiki, TheLou75, Citation bot 1, Pinethicket, Metricmike, Tardblog, HRoestBot, Abductive, PrincessofLlyr, 10metreh, Rameshngbot, Tom.Reding, Supreme Deliciousness, Lithium cyanide, RedBot, Brian Everlasting, Gingermint, Mohehab, Σ, Amitrc7th, Forward Unto Dawn, Mikebarryrocks!, Ras67, Fartherred, Skounave, IVAN3MAN, Tim1357, Crosscountry511, Kgrad,
FoxBot, Double sharp, TobeBot, Trappist the monk, Ksanexx, DixonDBot, Train2104, Arivu jevi, Tony24644, Vrenator, Begoon, Pilot850, Diannaa, Jhenderson777, Earthandmoon, Patsfanwow, Tbhotch, Рулин, Deanmullen09, Hornlitz, Sideways713, Shanefb, DARTH
SIDIOUS 2, Purz12, RjwilmsiBot, TjBot, Benyoch, Ripchip Bot, NerdyScienceDude, Burmiester, Wintonian, Slon02, DASHBot, EmausBot, John of Reading, WikitanvirBot, Oodgoo, Gfoley4, Inconsistentlysane, Ajraddatz, Pluszero, Giornorosso, GoingBatty, Heljqfy, Mar-
120
CHAPTER 7. VENUS
tinThoma, Gwillhickers, Wham Bam Rock II, Jmencisom, Challisrussia, K6ka, Japol1, Lamb99, AvicBot, ZéroBot, Stoner4life, Josve05a,
A2soup, Cosmoskramer, Emily Jensen, Nkwatra3, Noelwww, Jdixo17, Stickychew97, AvicAWB, Hevron1998, Aeonx, H3llBot, Eniagrom, NoOneAsked, Fabian Hassler, Ocaasi, Wabbott9, Samibrown98, Jman291, L1A1 FAL, 3sdanog, Boomchakalaka2, Brandmeister,
Alvez3, L Kensington, Dante51763, JeanPiaget, Surajt88, R1r1f2, Epicstonemason, Sailsbystars, Fanyavizuri, Kaijen176, Spongebob210,
Scoliosis, Johnny893, -xwingsx-, ChuispastonBot, Tehrandomguy101, Lee60480, Kkkylek, Planet photometry, Llightex, DASHBotAV,
Aussie895, Layneah, Whoop whoop pull up, Mssipress, Jonininini, ClueBot NG, Xession, Movses-bot, Jboratko, Frietjes, Dingowasher,
Habil zare, Kasirbot, Alexrybak, Helpful Pixie Bot, Vortex320, Bibcode Bot, BG19bot, MKar, Guy vandegrift, Hz.tiang, Qwerty1219, Frze,
AvocatoBot, Dodshe, Chris the Paleontologist, Cadiomals, Piisawesome, Jnanaranjan sahu, Cryptiddude, Sacchipersempr, Tratchy, Tycho
Magnetic Anomaly-1, Colinmartin74, Zedshort, Silvio1973, Ubiquinoid, Holyjoe722, BattyBot, Tonyhayes, Hansen Sebastian, Nick.mon,
Renilweb, EagerToddler39, Dexbot, Rezonansowy, Naapple, LightandDark2000, Mogism, Clockery, Siberian Patriot, Havebased123,
3er40, Typesometext, 134340Goat, JustAMuggle, Reatlas, Joeinwiki, Xwoodsterchinx, MinecraftFan2012, PC-XT, F6Zman, Jcpag2012,
SaturatedFats, Dustin V. S., Lindenhurst Liberty, Tony johnsong, CensoredScribe, Carbon6, JeanLucMargot, Exoplanetaryscience, Cptmrmcmillan, Anrnusna, Jamie.Taylor92, PlayStation 14, Monkbot, Allytoon, Filedelinkerbot, Scarlettail, Spideratseds, Tetra quark, Isambard
Kingdom, TheWhistleGag, Supdiop and Anonymous: 1408
• Mercury Source: http://en.wikipedia.org/wiki/Mercury?oldid=655885043 Contributors: RjLesch, The Cunctator, Lee Daniel Crocker,
Bryan Derksen, Zundark, Stephen Gilbert, -- April, Andre Engels, XJaM, Enchanter, Hephaestos, Olivier, Chuq, RTC, Eric119,
Minesweeper, Egil, KAMiKAZOW, TUF-KAT, Angela, Evercat, GCarty, Smack, Conti, Timwi, Dcoetzee, Ike9898, Doradus, DJ Clayworth, Morven, Joseaperez, Renato Caniatti, Jusjih, Flockmeal, Francs2000, Denelson83, Branddobbe, Rossnixon, Paul Klenk, Kristof vt,
Romanm, Academic Challenger, Steeev, Meelar, Hadal, Tobias Bergemann, Filemon, David Gerard, Thv, Marnanel, Monedula, Bkonrad, Curps, Bensaccount, Beardo, Matt Crypto, Joseph Dwayne, ChicXulub, Antandrus, The Singing Badger, Mzajac, A. J. A. DeWitt,
Nzseries1, Meweight, Icairns, Urhixidur, Ukexpat, JavaTenor, Andylkl, Freakofnurture, N328KF, Discospinster, Silence, Xezbeth, Alistair1978, Brian0918, CanisRufus, QuartierLatin1968, Deanos, T-bomb, Femto, Bobo192, Acntx, Kjkolb, A2Kafir, Linuxlad, Jumbuck,
Alansohn, QVanillaQ, Mo0, Velella, ReyBrujo, Yuckfoo, Suruena, Evil Monkey, De Guerre, TheCoffee, Eddie2, HenryLi, Kitch, Stephen,
Thryduulf, Pekinensis, Georgia guy, Barrylb, Julo, El Suizo, Shikai shaw, SeventyThree, Dovid, Palica, Dysepsion, Graham87, Marcg106,
Yuriybrisk, BD2412, Josh Parris, Canderson7, Twrist, Quiddity, Stardust8212, Feydey, Lordkinbote, Nightfreak, MooseBlaster, McPhail,
Demnevanni, RexNL, Gurch, Karrmann, King of Hearts, Chobot, EvilZak, Gwernol, YurikBot, Retodon8, No Account, Red Slash, Me and,
Qwertzy2, Hellbus, Havok, Kimchi.sg, Wimt, NawlinWiki, Rick lay95, Nick C, Zwobot, Wangi, Bota47, Hosterweis, Kal-El, Wknight94,
Theda, Fang Aili, §, Petri Krohn, 2fort5r, Curpsbot-unicodify, Chaiken, Katieh5584, Paul Erik, Serendipodous, Nofxjunkee, F, Herostratus, Prodego, The Monster, Unyoyega, Y control, Jrockley, Canthusus, Edgar181, Alsandro, Yamaguchi 先生, Gilliam, Hraefen, Chris the
speller, Agateller, MalafayaBot, Gareth, Bonni, Scwlong, MyNameIsVlad, Xyzzyplugh, Darwin's Bulldog, Addshore, Mipchunk, Nakon,
NaySay, Ultraexactzz, Jonmmorgan, Checco, JanderVK, Korean alpha for knowledge, Shlomke, Ckatz, Tetrachloromethane, JHunterJ,
SQGibbon, ShakingSpirit, BranStark, Clarityfiend, Epistemos, Trialsanderrors, Jontomkittredge, Markbassett, Tawkerbot2, MightyWarrior, JForget, CmdrObot, Tanthalas39, Ale jrb, Earthlyreason, Dycedarg, Makeemlighter, ShelfSkewed, Shield1785, Vectro, Gogo Dodo,
Anthonyhcole, Arrowned, Timmie.merc, Thijs!bot, Epbr123, Barticus88, Cain Mosni, John254, Kathovo, TXiKi, Wai Wai, Escarbot,
Caleson, Dainis, Charles Brooking, AntiVandalBot, Prolog, Fayenatic london, LibLord, Dougher, Ioeth, JAnDbot, NapoliRoma, RR,
LittleOldMe, Magioladitis, Gekedo, Bongwarrior, VoABot II, BrianMandell, AuburnPilot, Dulciana, Ohwell32, Enquire, Pax:Vobiscum,
Skaritista, MartinBot, Nando.sm, ViperBlade, Huzzlet the bot, Watch37264, J.delanoy, Child of Albion, Love Krittaya, SU Linguist,
Calvins48, Gzkn, Bigdumbdinosaur, Evil lemming, Jamesontai, WarFox, LordCo Centre, Cruftbane, Treisijs, Toll Booth Willie, Jamesryanjcrjcr, Num1dgen, Martial75, Lights, Hellno2, VolkovBot, Claudia rocks, Jeff G., Lear's Fool, Classical geographer, QuackGuru,
Philip Trueman, TXiKiBoT, Alan Rockefeller, Gerrish, Vanished user ikijeirw34iuaeolaseriffic, LeaveSleaves, UnitedStatesian, Kipicorn,
Kimjim, Madhero88, Sitacuisses, Chocolatemilk91, Brian Huffman, Billinghurst, Andy Dingley, Synthebot, Enviroboy, I will take over
wikipedia, Insanity Incarnate, Twooars, AlleborgoBot, PGWG, Milowent, Neparis, Vasili77, Udderguy, EJF, SieBot, TJRC, Tiddly Tom,
Jauerback, Caltas, Sinsom, Dattebayo321, Keilana, Pengzell, Screwed13927, Oda Mari, Jjkr, StaticGull, Mtaylor848, ClueBot, Engelalber,
Foxj, The Thing That Should Not Be, Drmies, CounterVandalismBot, SamuelTheGhost, Excirial, Mr.Z-man.sock, Quercus basaseachicensis, Alexbot, CrazyChemGuy, Net Hacker, Corysn123, NiciVampireHeart, NuclearWarfare, Jotterbot, Dustpelt96, BOTarate, Thingg,
Versus22, Miami33139, Budelberger, Skunkboy74, Wertuose, BodhisattvaBot, Rror, 13chaujf1, Netrat, On the other side, Addbot, Fyrael,
AlexWangombe, Fieldday-sunday, Skyezx, Download, FiriBot, Tassedethe, Williamhortner, DubaiTerminator, Tide rolls, Mjquinn id, Zorrobot, Bobers123, Luckas-bot, Yobot, Cflm001, Darfellan, ByM4k5, AVB, Tempodivalse, AnomieBOT, Nording, JackieBot, Theseeker4,
Materialscientist, Tinghokavin, Speculos, Parthian Scribe, MauritsBot, Xqbot, Berganus, Hys baby, Cureden, Capricorn42, Sup30, YBG,
Bayleo, Inferno, Lord of Penguins, GrouchoBot, Jezhotwells, RibotBOT, Jordan413, Qwesdfq, Aaa41, Bigboy004, Natural Cut, Ninunav,
A. di M., Emmyb11, SD5, Koobalocks, Saehrimnir, Lilnelly22, Pinethicket, Nickgonzalez, Achaemenes, RedBot, ContinueWithCaution, Shooting rox03, Cnwilliams, TobeBot, Ticklewickleukulele, Jburrows09, Qzm, Vrenator, Samsoup, JnRouvignac, Yellow Flash77,
MegaSloth, Ripchip Bot, Skamecrazy123, EmausBot, Tommy2010, Sepguilherme, Josve05a, GrouseyGrouse, Wayne Slam, Rcsprinter123,
DOwenWilliams, Ego White Tray, ChuispastonBot, DASHBotAV, Tvise1, ClueBot NG, Satellizer, Gaob, Rezabot, LOLSmileyMiley13,
Danim, Anupmehra, Wbm1058, Pratyya Ghosh, Longfellow300, DOOman68, Lugia2453, Basedastronomy69, Metru2000, Eyesnore,
Tentinator, Nickwilliams270203, Oliver hacker pro, TheEpTic, Phleg1, Riddleh, DarkxIllutionz, Dillyop, Bazinga.321 and Anonymous:
338
• Neptune Source: http://en.wikipedia.org/wiki/Neptune?oldid=654261627 Contributors: Paul Drye, Chuck Smith, Brion VIBBER, Mav,
Bryan Derksen, The Anome, Stephen Gilbert, Jeronimo, -- April, Ed Poor, Amillar, Eob, Scipius, Youssefsan, XJaM, Rmhermen, Christian List, Roadrunner, SimonP, B4hand, Montrealais, Chuq, Spiff, Frecklefoot, Michael Hardy, Oliver Pereira, Gdarin, Vera Cruz, Ixfd64,
(, Iluvcapra, Minesweeper, Alfio, Kosebamse, Egil, Looxix, Ahoerstemeier, William M. Connolley, Snoyes, Mark Foskey, Setu, Glenn,
Cyan, Poor Yorick, Evercat, Gh, Pizza Puzzle, Schneelocke, Hike395, Timwi, Denni, Colipon, Dandrake, Fuzheado, Doradus, Timc, DJ
Clayworth, Haukurth, Tempshill, Ed g2s, Rnbc, Head, Traroth, Shizhao, Mignon, Bloodshedder, Northgrove, Twang, Donarreiskoffer,
Branddobbe, Nufy8, Robbot, Naddy, Lowellian, Merovingian, Hadal, Wikibot, Dmn, Cutler, Dina, Alan Liefting, Ploum's, Dave6, Stirling Newberry, ShutterBugTrekker, Nephelin, Giftlite, JamesMLane, DocWatson42, Djinn112, Awolf002, Jyril, ShaunMacPherson, Harp,
Wolfkeeper, Obli, Everyking, Curps, Michael Devore, Henry Flower, JamesHoadley, MingMecca, Zaphod Beeblebrox, BrendanRyan, Pne,
AdamJacobMuller, Sesel, Wmahan, ChicXulub, SoWhy, Patteroast, Alexf, Semprini, Zeimusu, Junuxx, Vinay, Antandrus, The Singing
Badger, HorsePunchKid, Beland, Eroica, JoJan, Vanished user 1234567890, PDH, Rdsmith4, Thincat, Borameer, Gscshoyru, Neutrality, Urhixidur, Edsanville, Ukexpat, Lacrimosus, Mike Rosoft, Ouro, Venu62, Monkeyman, DanielCD, JTN, Indosauros, Discospinster,
Rich Farmbrough, Guanabot, Ponder, Arthur Holland, Mani1, MuDavid, Paul August, SpookyMulder, Kenb215, Bender235, Cyclopia,
Brian0918, RJHall, Ylee, El C, DS1953, Lankiveil, Joanjoc, Kwamikagami, Worldtraveller, Shanes, Tom, Hairyshoe, Remember, Art
LaPella, Femto, Iridia, Causa sui, Bobo192, Circeus, NetBot, BrokenSegue, Olve Utne, Elipongo, L33tminion, I9Q79oL78KiL0QTFHgyc,
Jerryseinfeld, Irrawaddy, Jojit fb, TheProject, Cherlin, BillCook, Sam Korn, Pharos, Supersexyspacemonkey, Storm Rider, Danski14, Bob
7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES
121
rulz, Alansohn, QVanillaQ, Verdlanco, Derumi, Axl, RoySmith, Alex '05, Spangineer, Avenue, VladimirKorablin, Snowolf, Burwellian,
Bucephalus, BaronLarf, SidP, Gdavidp, Almafeta, Suruena, Evil Monkey, Tony Sidaway, Jon Cates, RainbowOfLight, Inge-Lyubov,
Gene Nygaard, Capecodeph, Tobyc75, HenryLi, Sturmde, Kitch, TShilo12, Siafu, WilliamKF, Sterio, Bacteria, OwenX, Woohookitty,
BreathingMeat, JarlaxleArtemis, TigerShark, LOL, HisHighness420, BillC, Dayv, MONGO, Miss Madeline, Firien, Steinbach, Sengkang,
GregorB, Wayward, Smartech, Dysepsion, Paxsimius, Regulus32, Graham87, Marskell, Chun-hian, MC MasterChef, FreplySpang, Nlsanand, GrundyCamellia, Pentawing, Canderson7, Drbogdan, Rjwilmsi, Angusmclellan, Koavf, Virtualphtn, NatusRoma, Jake Wartenberg, Wikibofh, BlueMoonlet, Seraphimblade, Soakologist, Mike s, Mike Peel, XLerate, Kazrak, SeanMack, Brighterorange, Bhadani,
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Pleonic, Killervogel5, Jumbo Snails, Notyourbroom, SnoopY, SpuriousQ, Wikispork, Chaser, Hellbus, Shawn81, Rodasmith, Kerowren,
Hydrargyrum, Dotancohen, Stephenb, Zhatt, CambridgeBayWeather, Pseudomonas, Wimt, Burek, NawlinWiki, Wiki alf, BGManofID,
Johann Wolfgang, SomeYoungGuy, Mmccalpin, Toucan6, R'son-W, Dureo, Irishguy, Ravedave, Iggi.au, Chal7ds, Raven4x4x, Killdevil,
Zwobot, Ospalh, Nate1481, Rdl381, BOT-Superzerocool, PrimeCupEevee, DeadEyeArrow, Psy guy, T-rex, Dna-webmaster, Wknight94,
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Andy M. Wang, Teleros, Saros136, Bluebot, Kurykh, Keegan, Persian Poet Gal, Rick7425, Northern, Hibernian, The Rogue Penguin,
Kaid100, Oni Ookami Alfador, Ctbolt, Baa, DHN-bot, Sbharris, Chr.K., Bil1, AKMask, Gracenotes, Gyrobo, Lewis007, Scwlong, King of
the Dancehall, Can't sleep, clown will eat me, Shalom Yechiel, Fairychild, Mourn, Mrwuggs, Typofixer76, Astrobhadauria, Rrburke, Mhym,
Celarnor, AgentFade2Black, Fuhghettaboutit, Khukri, Nakon, Caniago, T-borg, Jennifer T, Metebelis, Kneale, Mini-Geek, Sbluen, Wizardman, Zonk43, Kendrick7, ALK, Er Komandante, Risker, Samuel Sol, Thebends, Ohconfucius, SashatoBot, Lambiam, Esrever, Xyad,
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Keller, CmdrObot, Ale jrb, Mattbr, Wafulz, Dycedarg, Ric36, Myrrhlin, Bumcheekcity, Vyznev Xnebara, Drinibot, CWY2190, Ruslik0, Benwildeboer, Dgw, WeggeBot, Logical2u, SelfStudyBuddy, Moreschi, Karenjc, RobertLovesPi, MrFish, Ufviper, Sopoforic, Cydebot, Natasha2006, Nbound, Abeg92, ChristTrekker, Treybien, Gogo Dodo, Ericfassbender, JFreeman, Corpx, Gv365, Q43, StaticElectric, Jc42, Kozuch, Lewisskinner, Omicronpersei8, Jeremy77q, TAIWAN, Rocket000, LukeS, Casliber, FrancoGG, Thijs!bot, JAF1970,
Epbr123, Wikid77, Jaxsonjo, Faigl.ladislav, Martin Hogbin, Illexsquid, Keraunos, Colosimo, Headbomb, Paper Clip Clock, Möchtegern,
John254, Bad Astronomer, Electron9, Ufwuct, Donnap1957, Wildthing61476, Davidhorman, Dfrg.msc, Pcbene, CharlotteWebb, The
Hybrid, Dawnseeker2000, Natalie Erin, RoboServien, SomeHuman, Escarbot, AntiVandalBot, Jeames, Jimspon7, Luna Santin, Opelio,
Erwin85Bot, Paste, BigThunderMtn, Dr. Submillimeter, Gdo01, Once in a Blue Moon, SkoreKeep, PresN, Raukodacil, JAnDbot, Deflective, Husond, MER-C, BlindEagle, James919, Instinct, Kaabi, Db099221, Andonic, Hut 8.5, Rentaferret, PhilKnight, Rothorpe, Acroterion, SteveSims, Bencherlite, ArthurianLegend, WolfmanSF, BMW Z3, Freedomlinux, Pedro, Murgh, VoABot II, Mileage, Tomhannen, Think outside the box, Rivertorch, Bigdan201, Midgrid, Gr1st, Bubba hotep, BrianGV, Catgut, Animum, Pausch, Cyktsui, ArthurWeasley, Randoman412, 28421u2232nfenfcenc, BilCat, Benny d, Chivista, Romancer, Glen, Chris G, DerHexer, JaGa, Megalodon99,
Lenticel, WLU, TheRanger, The Sanctuary Sparrow, Kheider, Gwern, Mithras6, Jasonater, MartinBot, FlieGerFaUstMe262, Kingw0ng,
Nohsvideoguy, Arjun01, Sunbursts, Hugo Dufort, Rettetast, Roastytoast, Juansidious, Cosumel, Keith D, Ambi Valent, Mschel, CommonsDelinker, AlexiusHoratius, Hengist100, CASfan, Pbroks13, Dorieo21, Arpierson, Smokizzy, Ducksauce101, Artaxiad, SedatedGodzilla, Beehive101, Paranomia, Watch37264, J.delanoy, Captain panda, DrKiernan, Trusilver, Planemo, AstroHurricane001, Ali, Bogey97, Lizrael, Mnshacodi, BillWSmithJr, Nigholith, GuitarFreak, WarthogDemon, E. Schenk, Acalamari, Stompin' Tom, Bot-Schafter,
Katalaveno, Mr Rookles, Superiorrob, Gman124, Jeepday, Skier Dude, AntiSpamBot, Richard D. LeCour, NewEnglandYankee, Srpnor, Theawsomelife, Rominandreu, Fountains of Bryn Mawr, SmilesALot, Ohms law, SJP, Toon05, Mufka, Shoessss, Thundergoalie73,
MetsFan76, Renvarian, Cmichael, Atropos235, Evb-wiki, RB972, Seventypercent, Spiral Wave, U.S.A.U.S.A.U.S.A., Syu9019, Mjzwick,
Arvind Vyas, Doctoroxenbriery, Jarry1250, Useight, Abasher, Planetwaves, DeadHd1995, GrahamHardy, CardinalDan, Idioma-bot, Kazooieman, Isayyum, Fainites, Stewader, Flatline121313413, PeaceNT, Chinneeb, Georgetherock, Deor, King Lopez, ThrustVectoring,
VolkovBot, Thedjatclubrock, Johan1298, Choft, Leebo, Nburden, Mike=200006, Alexandria, AlnoktaBOT, Toddles29, Rutherfordjigsaw,
Katydidit, Boaex, Alexkorn, Station1, Philip Trueman, Amos Han, TXiKiBoT, GimmeBot, SwiftAce, Maximillion Pegasus, Hqb, Qaletaqa,
TheresJamInTheHills, Rei-bot, Ann Stouter, Z.E.R.O., Google92, Yovinedelcielo, Qxz, Retiono Virginian, Lradrama, Seraphim, Melsaran,
MasterSci, Leafyplant, Broadbot, Raymondwinn, Seb az86556, Pleroma, UnitedStatesian, Picturef1, Emilyxo1017, Imagecrafting, Amstoakes, Kipicorn, Maxexcloo, Hello556, Orange-kun, Soccergirl9867, BigDunc, Roland Kaufmann, Pious7, Milkbreath, Sarc37, Go-in,
Enviroboy, Imsamuel6, Brandonvas, Sylent, Insanity Incarnate, Ceranthor, AlleborgoBot, Suresh Nat, Funeral, King food, Tvinh, Oklabama, Moofman22, Jeodo, School134524, Bensational, Steven Weston, Oceanball, EJF, SieBot, Dudeofdude2123, Kfc1864, Jim77742,
Tresiden, Akliman, PlanetStar, Tiddly Tom, Work permit, Scarian, Euryalus, ToePeu.bot, Oldag07, Spacedrive, KGyST, Jsc83, Caltas,
Universe=atom, Latin pimp, Nickyddogg, Yintan, Keilana, Iames, RadicalOne, Exert, Comkidwizzer3, Ooodrey19, Oda Mari, Arbor to SJ,
Sohelpme, Pigger500, EastCoastPwnerz, Bram358, Hahaha34, Ayudante, 712yo, Oxymoron83, Aminghane, Faradayplank, AngelOfSadness, Lightmouse, Poindexter Propellerhead, Zacplaysgames, Murlough23, Mollykate8, Torchii, BenoniBot, Halcionne, Macy, Diego Grez,
Dannyfat, Spliffmon, Maelgwnbot, LonelyMarble, Alatari, Jacob.jose, Randomblue, Hamiltondaniel, Venom124, Dust Filter, Nergaal,
Efe, Spirit13, Jons63, Escape Orbit, AndySmith84, C0nanPayne, Starcluster, Shrewpelt, Kanonkas, Freewayguy, Troy 07, BHenry1969,
ClueBot, LAX, Artichoker, PipepBot, Bobathon71, Rjd0060, Lawrence Cohen, Bobisbob, Shinpah1, Jimfandango, Jdford10, Jed Bartlet,
CounterVandalismBot, Hhhhhsfvg, Blanchardb, Neverquick, ChandlerMapBot, Klm815, DragonBot, Stepshep, SapientiaSativa, Robert
Skyhawk, Excirial, AssegaiAli, Loph10, Alexbot, CrazyChemGuy, Gtstricky, Leonard^Bloom, Vivio Testarossa, Rhatsa26X, Sun Creator,
NuclearWarfare, Arjayay, Jotterbot, PhySusie, Ember of Light, CowboySpartan, Razorflame, Radtek67, TOSYuan3195, BOTarate, Starblazer123, Thingg, Ababababababab, Aitias, Wcp07, ClanCC, Anubad95, Neuralwarp, Cgallstar27, Swift as an Eagle, Dtpeck, Mattrave,
Dora-bobba, 68Kustom, Coopman86, Badgernet, WikiDao, JinJian, 0pulse, MystBot, Mvgirl13, NFRANGA, Hunter Kahn, Kbdankbot,
Jtknowles, Eello555, Sunsetsunrise, RX8Chic, Roentgenium111, AVand, Some jerk on the Internet, Rini genes, I eat gym socks, DOI bot,
Element16, TutterMouse, CanadianLinuxUser, Ronkonkaman, Heremod, LaaknorBot, Delaszk, Stevethepirate1001, Rickybobby1001,
Shortkicks4, Ghsfan13, LinkFA-Bot, Vivelafranceduex, EvelynFl, Flanagan33, Chicken likin, Numbo3-bot, Sc8erboi42, Ehrenkater, Tide
122
CHAPTER 7. VENUS
rolls, Lightbot, OlEnglish, Gail, Azdel, Cote d'Azur, Luckas-bot, Yobot, Ptbotgourou, II MusLiM HyBRiD II, Aldebaran66, Monkeydoo412, YngNorman, Dickdock, DanTheMan702, Hybridcar1, AnomieBOT, Archon 2488, Galoubet, Materialscientist, Frankietang,
Citation bot, ArthurBot, Dspetc, Jlg4104, MauritsBot, Xqbot, Timir2, Smk65536, Amore Mio, Jmundo, Srich32977, Almabot, GrouchoBot, Ataleh, SassoBot, Jalapenos do exist, The Wiki ghost, Doulos Christos, Modestas rukky, Dnywlsh, Pikaman, Bff98765, GNRY09,
Conrad, 16 year old girl, Doowop13579, Sk8erdude22, Tyroni96, Qwerty on Willy, Mommy87675, 911alloveragain911, Bryschneider,
Coolestmidget13, Taravellacane, Silbad, Cookay569, Jorgie1, Fotaun, FrescoBot, LucienBOT, Lookang, Dalyup!, Bill the Cat 7, Armigo,
Kobrabones, HRoestBot, Jonesey95, Tom.Reding, RedBot, Lars Washington, MastiBot, Googlemeister, Fartherred, IVAN3MAN, Lightlowemon, FoxBot, Double sharp, Trappist the monk, PS3ninja, Stephen MUFC, Gondor2222, Tbhotch, Shanefb, RjwilmsiBot, TjBot,
Alph Bot, Burmiester, Kiko4564, DASHBot, EmausBot, Hoosier1989, WikitanvirBot, Qurq, Gored82, Jmencisom, P. S. F. Freitas, Nothing149, ZéroBot, CanonLawJunkie, Josve05a, A2soup, Nicolas Eynaud, AvicAWB, Hevron1998, H3llBot, Mlpearc Public, Мл.научный
сотрудник, L Kensington, Richard Tuckwell, Silliking, Sailsbystars, MarkHurn, Adelson Velsky Landis, Honesty First, ChuispastonBot,
Fjörgynn, ClueBot NG, Inoyu49, Faber01, Yanclae, Lanthanum-138, Delusion23, Castncoot, Diyar se, Helpful Pixie Bot, Newyork1501,
Gob Lofa, Bibcode Bot, Dalit Llama, MKar, Lo Ximiendo, Hz.tiang, Leonxlin, AvocatoBot, Dodshe, Gallina3795, AstroRobster, Cadiomals, Rgbc2000, Tycho Magnetic Anomaly-1, Ubiquinoid, Et Cum Spiritu Tuo, SoylentPurple, DarafshBot, W.D., Kelvinsong, Asisman, Dexbot, AaronMP84, JustAMuggle, Reatlas, Redd Foxx 1991, Jcpag2012, JPaestpreornJeolhlna, Dustin V. S., Lindenhurst Liberty,
SeventeenTurtle, YoungDrac, UltraMario64, Exoplanetaryscience, Stamptrader, Cancina5645, PlayStation 14, Monkbot, Trackteur, Spiderjerky, Tetra quark, Isambard Kingdom and Anonymous: 1328
• Saturn Source: http://en.wikipedia.org/wiki/Saturn?oldid=655790788 Contributors: Magnus Manske, Derek Ross, Brion VIBBER, Mav,
Bryan Derksen, Malcolm Farmer, -- April, Mark, Ed Poor, Andre Engels, Eob, Scipius, XJaM, JeLuF, Rmhermen, Christian List, SimonP,
Camembert, Fonzy, Spiff, D, JohnOwens, Michael Hardy, Tim Starling, Lexor, MartinHarper, Gabbe, Ixfd64, Frank Shearar, Delirium,
(, Iluvcapra, Minesweeper, Alfio, Tregoweth, Egil, Looxix, Ihcoyc, Ahoerstemeier, Caid Raspa, Rlandmann, Setu, Julesd, Glenn, Poor
Yorick, Nikai, Andres, Kaihsu, Evercat, Mxn, Schneelocke, Mechanolatry, Hike395, Hashar, The Tom, Timwi, David Newton, Fuzheado,
Doradus, Haukurth, Maximus Rex, Dragons flight, Saltine, Tempshill, Omegatron, Ed g2s, Head, Thue, Spikey, Traroth, Bloodshedder, Secretlondon, Jerzy, Flockmeal, GPHemsley, Lumos3, Denelson83, Chuunen Baka, Donarreiskoffer, Branddobbe, Robbot, Ke4roh,
Sander123, ChrisO, Korath, Chris 73, Dirgela, R3m0t, Naddy, Academic Challenger, Puckly, Rursus, Hemanshu, Hadal, JackofOz, Lupo,
HaeB, Cyrius, Dina, Robert Happelberg, Psb777, ShutterBugTrekker, Nephelin, Giftlite, DocWatson42, Christopher Parham, Marnanel,
Djinn112, Awolf002, Jyril, Harp, Inter, Wolfkeeper, Rbs, Obli, Sage Erk, Bradeos Graphon, Peruvianllama, Wwoods, Everyking, No Guru,
Maha ts, Curps, Michael Devore, JamesHoadley, Cantus, Waltpohl, BrendanRyan, Macrakis, Python eggs, SWAdair, Edcolins, Golbez,
Peter Ellis, ChicXulub, Auximines, Patteroast, Alexf, Geni, J, CryptoDerk, Antandrus, The Singing Badger, HorsePunchKid, Beland, MisfitToys, Vanished user 1234567890, Melikamp, PDH, Jossi, Rdsmith4, Mzajac, Tomruen, Satori, Icairns, Egan Loo, Marcos, Asbestos,
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SpookyMulder, Panoramastitcher, Bender235, ESkog, Neurophyre, Kbh3rd, Kaisershatner, Petersam, JohnLynch, Brian0918, RJHall,
Ylee, Project2501a, El C, Lankiveil, Joanjoc, Kwamikagami, Worldtraveller, Aude, Shanes, Tom, Remember, Sietse Snel, Art LaPella,
RoyBoy, Femto, Bobo192, NetBot, Hurricane111, Aetherfukz, Smalljim, Olve Utne, Viriditas, Chessphoon, I9Q79oL78KiL0QTFHgyc,
La goutte de pluie, Matt McIrvin, TheProject, BillCook, Sam Korn, Polylerus, Pearle, Gsklee, Jonathunder, Hooperbloob, Jjron, Eddideigel,
Mareino, Wayfarer, KeesCook, Stephen G. Brown, Bob rulz, Alansohn, Gary, Burzum, Andrew Gray, A.T.M.Schipperijn, El stiko, Riana,
Lectonar, Lightdarkness, Mac Davis, Mysdaao, Spangineer, Snowolf, Ross Burgess, Icewolf34, BRW, Tony Sidaway, CloudNine, Drat,
Sciurinæ, Inge-Lyubov, LFaraone, Humble Guy, Kusma, Reaverdrop, Gene Nygaard, Dan East, HenryLi, Kazvorpal, Kitch, Ericl234, Gatewaycat, Stephen, Siafu, Dracogen, WilliamKF, Rorschach, Firsfron, TigerShark, LOL, Tom Ameye, Uncle G, BillC, Madchester, MONGO,
Bennetto, Schzmo, Gengiskanhg, Bbatsell, Pufferfish101, Sengkang, Eyreland, SDC, Brendanconway, とある白い猫, Alec Connors,
LinkTiger, Smartech, Dysepsion, MrSomeone, Aarghdvaark, Graham87, KyuuA4, Magister Mathematicae, Galwhaa, FreplySpang, Eteq,
NebY, Icey, Edison, Josh Parris, Pentawing, Canderson7, Drbogdan, Akubhai, Sjakkalle, Rjwilmsi, Koavf, Vary, Rgerhards, BlueMoonlet,
JHMM13, Tawker, Mike Peel, Kazrak, HappyCamper, Bhadani, OKtosiTe, Yamamoto Ichiro, Marsbound2024, Titoxd, SchuminWeb,
Mumblingmynah, RobertG, Dan Guan, Doc glasgow, Latka, Dave1g, Crazycomputers, Avalyn, Nivix, Shadow007, RexNL, Gurch, Brimcmike, Arctic.gnome, TeaDrinker, Srleffler, Le Anh-Huy, Phoenix2, King of Hearts, Urzeitlich, Chobot, DaGizza, Mordicai, DVdm, Gwernol, E Pluribus Anthony, Wjfox2005, Wavelength, TexasAndroid, Spacepotato, RattusMaximus, Kinneyboy90, Hairy Dude, TSO1D,
Jimp, Brandmeister (old), Kymacpherson, Prometheus235, RussBot, Zafiroblue05, Chuck Carroll, CanadianCaesar, Hellbus, Stephenb,
Gaius Cornelius, Oni Lukos, Wimt, Ugur Basak, NatureBoy, Shanel, NawlinWiki, Wiki alf, BGManofID, Daemon8666, Mike18xx, Testtools, Grafen, NickBush24, Itisan, SivaKumar, RazorICE, Howcheng, Robchurch, Nick, Aaron Brenneman, Tjarrett, Xdenizen, Jryden,
Chal7ds, Rmky87, Raven4x4x, Voidxor, Grafikm fr, Tony1, Zwobot, Syrthiss, T, Samir, DeadEyeArrow, PS2pcGAMER, CorbieVreccan,
Fbergo, Darkfred, Wknight94, Mkns, Deville, Phgao, Zzuuzz, Kandrey89, Ageekgal, Nikkimaria, Lorenzo Braschi, JRawle, Zobovor,
Rlove, JoanneB, Alasdair, MrBook, Brianlucas, CWenger, Kier07, Hurricane Devon, Wainstead, Echartre, Geoffrey.landis, JLaTondre,
Wootini, Ybbor, Tarquin Binary, Katieh5584, Kungfuadam, GrinBot, Iago Dali, Serendipodous, Mejor Los Indios, DVD R W, CIreland,
Bibliomaniac15, Crusty007, AndrewWTaylor, Caponer, Deuar, Sardanaphalus, Crystallina, A bit iffy, GrafZahl, SmackBot, Amcbride,
Nihonjoe, KnowledgeOfSelf, Martin.Budden, Pavlovič, Blue520, Speight, Kilo-Lima, KocjoBot, Jagged 85, RlyehRising, EncycloPetey,
Delldot, Paxse, Fnfd, HalfShadow, Onsly, Gilliam, Ohnoitsjamie, Hmains, Betacommand, Skizzik, Andy M. Wang, Weirdoactor, Valley2city, Saros136, Endroit, AstroMalasorte, Bluebot, Kurykh, Geneb1955, Persian Poet Gal, Pylori, MalafayaBot, Hibernian, Saturn7,
DHN-bot, Roy Al Blue, EddieSegoura, Zsinj, Can't sleep, clown will eat me, John Hyams, CharlesJS, Mrwuggs, Rogpyvbc, Nixeagle,
OSborn, Avb, Astrobhadauria, TheKMan, Aces lead, Rsm99833, Addshore, Whpq, Edivorce, Amazins490, SundarBot, Lathal, Krich, Cybercobra, Bowlhover, Nakon, T-borg, Theodore7, Metebelis, Gerph, Daniel bg, Mini-Geek, Battamer, Eynar, Jklin, Drc79, Wizardman,
Glenn Browne, Zonk43, Ericl, S@bre, Salamurai, Sarfa, Plilja, SashatoBot, Dane Sorensen, Garywill, Nishkid64, CFLeon, Harryboyles,
Attys, Axem Titanium, Dbtfz, Molerat, Vanished user 9i39j3, Kuru, John, WhiteCat, Scientizzle, Shirifan, Heimstern, Breno, Gardner.DJ,
Benesch, JorisvS, Temple, JayMan, Minna Sora no Shita, Goodnightmush, Ocatecir, Jess Mars, PseudoSudo, Ckatz, The Man in Question, RandomCritic, OzOz, Slakr, Werdan7, Tac2z, Mr Stephen, Godfrey Daniel, SandyGeorgia, Tuspm, Artman40, Ryulong, RichardF,
AEMoreira042281, Elb2000, Jose77, Atakdoug, Darry2385, Johnny 0, Hu12, Politepunk, Michaelbusch, Dekaels, Vespine, Laurens-af,
Joseph Solis in Australia, Shoeofdeath, Newone, StephenBuxton, Joao.caprivi, TurabianNights, Espi, Courcelles, Tawkerbot2, Bubbha,
Cryptic C62, Poolkris, Lavaka, Orangutan, MightyWarrior, SkyWalker, Dia^, J Milburn, Spacini, JForget, GeneralIroh, CmdrObot, Tanthalas39, Ale jrb, Dycedarg, Morganfitzp, KyraVixen, Drinibot, DeLarge, Charvex, Ruslik0, Benwildeboer, Dgw, AshLin, Lazulilasher,
WeggeBot, Some P. Erson, Moreschi, MrFish, Myasuda, RagingR2, Ufviper, Cydebot, Nbound, Nebular110, -S TANK-, Stilwebm, Mike
Christie, Steel, Evm123, Michaelas10, Gogo Dodo, Carl Turner, Travelbird, Bazzargh, ST47, Porsche997SBS, Grinning Fool, Master
son, Tdvance, Tawkerbot4, Demomoke, DumbBOT, Chrislk02, FastLizard4, Bryan Seecrets, Ssilvers, Sockr44e, Omicronpersei8, UberScienceNerd, ArminHammer, Casliber, Croocroo123, Thijs!bot, Pajz, Jordan11111, LeeG, Kablammo, Keraunos, Andyjsmith, Pampas
7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES
123
Cat, Young Pioneer, Oliver202, Headbomb, Dayn, John254, Neil916, Kathovo, Topquark170GeV, Cool Blue, Lars Lindberg Christensen,
Davidhorman, The Proffesor, E. Ripley, CielProfond, Pcbene, Lithpiperpilot, BlytheG, Big Bird, RaNdOm26, Dawnseeker2000, Natalie Erin, SomeHuman, Futurebird, Eleuther, Spud Gun, AntiVandalBot, Yupik, Luna Santin, Yr41193, Seaphoto, 105706, Peter50,
Dpmcnevin, Quintote, DarkAudit, Dr. Submillimeter, Gdo01, Spencer, SkoreKeep, Altamel, Cbrodersen, Myanw, Uchohan, PresN,
JAnDbot, Dan D. Ric, Deflective, MER-C, CosineKitty, LoveCowboy2024, Andonic, Igodard, Hut 8.5, Rentaferret, Rothorpe, Denimadept, Acroterion, SteveSims, WolfmanSF, Murgh, Bongwarrior, VoABot II, AuburnPilot, Wikidudeman, JNW, SpazKitty, Repoed2,
‫باسم‬, Bigdan201, CTF83!, Diego bf109, Jespinos, Michele123, Twsx, Midgrid, Jkake, Than217, Catgut, Panser Born, PIrish, Animum, Cyktsui, BatteryIncluded, ArthurWeasley, Gruby22, Loonymonkey, BilCat, Hamiltonstone, Allstarecho, Thehalfone, SpaceGuide,
Pha0001, Shijualex, DerHexer, Edward321, WLU, Patstuart, Info D, WildRichLord, Revcph1958, Kheider, Pikolas, Gwern, NatureA16,
Gjd001, MasterRadius, MartinBot, GM11, Racepacket, Arjun01, Poeloq, Rettetast, Roastytoast, Ambi Valent, Knayil, Averross, Ryan
dude200, CommonsDelinker, Oysta, AlexiusHoratius, Pbroks13, PrestonH, Redian, Watch37264, J.delanoy, Pharaoh of the Wizards,
DrKiernan, Trusilver, Svetovid, Asqwce, Ali, Lizrael, Hans Dunkelberg, Nigholith, Ginsengbomb, Clilly, KeybladeSephi, Kudpung, Gzkn,
ABTU, St.daniel, Bot-Schafter, Gman124, Dfoofnik, Langara College, Gurchzilla, AntiSpamBot, (jarbarf), Berserkerz Crit, SuzanneKn,
Hut 6.5, Belovedfreak, Blackvanillasky, Bushcarrot, NewEnglandYankee, Aquatics, Sculptorjones, Enguarde, Fjbfour, Potatoswatter,
MetsFan76, Cmichael, Yoyo01, Cometstyles, WJBscribe, Aminullah, Tygrrr, SBKT, Aucahuasi, King Toadsworth, Mike V, Redrocket,
Songjin, Kvdveer, Pdcook, Jarry1250, Jerry106, Legend=me, Idioma-bot, V vangipuram, Redtigerxyz, Black Kite, Lights, PeaceNT, Deor,
VolkovBot, CWii, Johan1298, Jlaramee, Claudia rocks, SarahLawrence Scott, AlnoktaBOT, HeckXX, Toddles29, Rutherfordjigsaw, Katydidit, Boaex, Philip Trueman, Jjpulczinski, TXiKiBoT, SwiftAce, Pyromaniaque, Malinaccier, Qaletaqa, Alanspence, GDonato, Miranda,
Ann Stouter, Z.E.R.O., DocGratis, Paulfrank523, Qxz, Piperh, DennyColt, Bass fishing physicist, MasterSci, Leafyplant, Voiceofreason01, Sanfranman59, Happy2bback2, Abdullais4u, DoktorDec, Wassermann, Seb az86556, Ollige, Cremepuff222, Bearian, Rzhevski,
CO, Pious7, Killing sparrows, MacTire, Rusica9231, Meesheek, Angrymansr, Synthebot, Su37amelia, Strangerer, Lovlymaddie, Mar vin
kaiser, Patyoda, WatermelonPotion, Insanity Incarnate, Hinomaru kun, Sue Rangell, AlleborgoBot, Legoktm, NHRHS2010, EmxBot,
Tedstryk, SquallLeonhart ITA, D. Recorder, Jk lol haha, Mehungy, ColinKelly, Moonmayne21, Guambomb, SieBot, Chronic Stoned
Emo Ranger, Jim77742, Gtownhoyas34, PlanetStar, Tiddly Tom, Dwadejames03, Graham Beards, Scarian, Malcolmxl5, BotMultichill,
ToePeu.bot, Oldag07, Gerakibot, Tonyvz, Miaie, Dawn Bard, Caltas, Overachievers, Universe=atom, Sk8drummerd, Mvierow, Lucasbfrbot, Iamdaddysgirl, Rach-ach, Normz, WildWildBil, GlassCobra, Yulu, Purbo T, Kayla Norris, Liltlover, Purplepickle10, Keilana,
RadicalOne, Tiptoety, Radon210, Editore99, Oda Mari, Mimihitam, Oxymoron83, BartekChom, 2djay7, KPH2293, Hello71, Steven
Zhang, Lightmouse, Poindexter Propellerhead, Kcrocetti, Murlough23, Astrale01, Voltron, BenoniBot, YMama, Kudret abi, Freescrues,
LonelyMarble, Torchwoodwho, Mojoworker, Rocksanddirt, Anyeverybody, Trashbird1240, Driftwood87, Dabomb87, Neo., Nergaal,
C0nanPayne, Raasgat, Wjmummert, Velvetron, Tatterfly, ImageRemovalBot, Athenean, Yeah01011, Faithlessthewonderboy, Martarius,
Stuart7m, ClueBot, LAX, PipepBot, Mroctoberfest, Fyyer, Foxj, The Thing That Should Not Be, Swapnils2106, Jan1nad, Wwheaton,
Jesterrx, Teggstar1998, Higgins403, SuperHamster, ANSIFY 303, CounterVandalismBot, Laylarockmisocks, EconomicsGuy, Blanchardb,
Igotmesomebathinapes, TarzanASG, Piledhigheranddeeper, Neverquick, Lampofdoom, DragonBot, Meweee, Excirial, Pumpmeup, TonyBallioni, Mandtplatt, Vivio Testarossa, Sun Creator, Jotterbot, PhySusie, Ember of Light, SockPuppetForTomruen, Bennyvk, BOTarate,
Thingg, Darren23, Aitias, Greendog624, Alexkerkove, MelonBot, Lethalstrike5, ClanCC, Thikr, Arianewiki1, XLinkBot, Tylerluvsthevag,
Forever unkown, Dark Mage, Mattrave, Sanjay517, Andrew Hing, Locoshonmachon, Tegles, Baileyboo1230, BOBBYFATSO, Thevyan,
Thetwizzler150, Veenluk, Trevaqueline Mitchand, Ririri, JinJian, MystBot, Parejkoj, Koraki, Nerd geek, Sandman 445sss, Kbdankbot,
Frenchyfrog, Brclarke, Hawkania, Ryryz666, Cbrooks91671, Kenpachi872, Threechanger, AVand, Some jerk on the Internet, Lol vandal
992, Lagus970, Talbballer, Bkhreal, DOI bot, SakuraKaira, Biggins96, Ronhjones, Mac Dreamstate, Heremod, Aselfcallednowhere, Ka
Faraq Gatri, Kwer.rewk, Ccacsmss, Glane23, Chzz, Debresser, LinkFA-Bot, 5 albert square, 84user, Numbo3-bot, DubaiTerminator, Teles,
Ettrig, Webwizard, Ben Ben, Luckas-bot, Yobot, Ptbotgourou, KamikazeBot, Dmarquard, AnomieBOT, Thuvan Dihn, Erdunbar, A More
Perfect Onion, Archon 2488, SaiyanEmperor2008, Bsimmons666, Jim1138, Materialscientist, Citation bot, E2eamon, GB fan, ArthurBot,
Xqbot, Link dude177, Timir2, Smk65536, KuRiZu, Werner65, Mlpearc, Srich32977, Almabot, Arsia Mons, GrouchoBot, Nayvik, Ataleh,
Hallen455, RibotBOT, SassoBot, ‫قلی زادگان‬, Amaury, Charvest, Mangst, Shadowjams, Dico Calingal, Fotaun, Thehelpfulbot, FrescoBot,
Dogzrule101, LucienBOT, Originalwana, Ceciliarozzie, Tobby72, Io Herodotus, Lookang, KokkaShinto, WarpCode, Goodbye Galaxy,
Qfissler, HJ Mitchell, Louperibot, OgreBot, Kobrabones, Pinethicket, I dream of horses, HRoestBot, Tom.Reding, MJ94, RedBot, Σ, Forward Unto Dawn, IVAN3MAN, Lightlowemon, FoxBot, Double sharp, TobeBot, Trappist the monk, Mrauscher, Orb85750, Rickky678,
Vrenator, Krusberg, Aoidh, Seahorseruler, Diannaa, Stephen MUFC, ThinkEnemies, Suffusion of Yellow, Tbhotch, Minimac, Reepy1,
DARTH SIDIOUS 2, Ashishindemand, RjwilmsiBot, HxCUNstopABLE, Burmiester, DASHBot, Mr. Anon515, EmausBot, John of Reading, Tuankiet65, WikitanvirBot, Cbornmann, Racerx11, GoingBatty, Gwillhickers, Jmencisom, K6ka, P. S. F. Freitas, ZéroBot, John Cline,
Fæ, Josve05a, A2soup, EdEColbert, Dffgd, Access Denied, Hevron1998, H3llBot, Wiooiw, Cline92, Wayne Slam, RaptureBot, L1A1
FAL, Δ, Brandmeister, Inimbrium, Stephenj642, L Kensington, Victor98, MonoAV, Donner60, Breebreebjg, Sailsbystars, ChuispastonBot,
Camero09, Hylian Auree, LikeLakers2, GrayFullbuster, Sven Manguard, DASHBotAV, Pook261998, Gary Dee, Splush23, ClueBot NG,
Haromonos.haromonos3, TheWord77, Gilderien, Satellizer, Bobtedd123, KDS444, Beth.chattin, Xession, Loginnigol, Lanthanum-138,
All Hail Hypnotoad!, O.Koslowski, Rezabot, SenseiAC, Widr, Danim, SentientSystem, Voldemortal, Diyar se, Helpful Pixie Bot, Bibcode
Bot, Lowercase sigmabot, Pine, MKar, MusikAnimal, SpaceChimp1992, Frze, AvocatoBot, Mark Arsten, Cadiomals, Writ Keeper, Harizotoh9, Tycho Magnetic Anomaly-1, Colinmartin74, WikiAnaUser., Ubiquinoid, Nelg, Carliitaeliza, Hansen Sebastian, Plutoniumjesus,
ChrisGualtieri, Soulparadox, Kelvinsong, Dexbot, KDaxs, Anderson, Lugia2453, Sidelight12, Omgpoo, 93, Max14182000, JustAMuggle, Jake zahnzinger, Reatlas, Joeinwiki, Haribo2000, PinkAmpersand, Reed92, Bowwow828, Sreek123, Pink699, Fuhfue, Jcpag2012,
2001littlekaty, Runar98, Chetan8945, Albow7, Stub Mandrel, Kelleynoah123, Zenibus, Mirvworks, Antn123, Flygonfan42, John123456jk,
Blackfire123, Ginsuloft, Exoplanetaryscience, Asherdancemachine, Heatfan9876, Theblogman44, Kn1467, Cancina5645, PlayStation 14,
Monkbot, Dogov, Plokmijnuhbygvtfcdxeszwaq, Spiderjerky, Tetra quark, Isambard Kingdom, FlorZi, TheWhistleGag and Anonymous:
1550
• Uranus Source: http://en.wikipedia.org/wiki/Uranus?oldid=651174965 Contributors: RjLesch, Derek Ross, Lee Daniel Crocker, Brion
VIBBER, Vicki Rosenzweig, Mav, Bryan Derksen, Malcolm Farmer, -- April, Ed Poor, Amillar, Andre Engels, Eob, Scipius, Danny,
XJaM, JeLuF, Christian List, PierreAbbat, William Avery, SimonP, Ramin Nakisa, Fonzy, Spiff, Frecklefoot, Michael Hardy, Tim Starling, Oliver Pereira, DopefishJustin, Bobby D. Bryant, Ixfd64, Delirium, Minesweeper, Alfio, Egil, Looxix, Ahoerstemeier, Notheruser,
Mark Foskey, Julesd, Glenn, Poor Yorick, Netsnipe, Andres, Evercat, Gh, Mxn, Ilyanep, Schneelocke, Hike395, Charles Matthews, Timwi,
Wikiborg, Doradus, Tpbradbury, Ed g2s, Head, Traroth, Bloodshedder, Raul654, Dysfunktion, Wetman, Jerzy, Northgrove, Donarreiskoffer, Branddobbe, Robbot, Juro, Dale Arnett, Fredrik, Tomchiukc, RedWolf, Naddy, Babbage, Merovingian, Zulugrid, Rursus,
Timrollpickering, Bkell, Hadal, Robinh, Dina, Radagast, Robert Happelberg, Snobot, ShutterBugTrekker, Nephelin, Giftlite, DocWatson42, MPF, Marnanel, Djinn112, Awolf002, Jyril, Oberiko, Gil Dawson, Harp, Wolfkeeper, Nunh-huh, Tom harrison, Monedula, Peruvianllama, Wwoods, Everyking, No Guru, Curps, Michael Devore, JamesHoadley, MingMecca, Thetorpedodog, Niteowlneils, Bren-
124
CHAPTER 7. VENUS
danRyan, Python eggs, DÅ‚ugosz, Bobblewik, Golbez, Wmahan, ChicXulub, Steuard, Patteroast, Alexf, Gdm, Sonjaaa, Antandrus, The
Singing Badger, HorsePunchKid, Mustafaa, Beland, Vanished user 1234567890, Jossi, Rdsmith4, Kesac, DragonflySixtyseven, Satori,
Icairns, Arcturus, Gscshoyru, Asbestos, Martin.komunide.com, Neutrality, Urhixidur, Edsanville, Ensrifraff, Positron, Jcw69, Laisak,
Adashiel, Trevor MacInnis, Mormegil, Freakofnurture, JTN, Nido, Discospinster, Rich Farmbrough, Guanabot, C12H22O11, Vsmith,
ArnoldReinhold, Will2k, Wadewitz, MuDavid, Paul August, SpookyMulder, Night Gyr, Bender235, ESkog, Kbh3rd, Joeconsumer, The
Iconoclast, Kalel, Loren36, Violetriga, Brian0918, RJHall, Sfahey, El C, Lankiveil, Kwamikagami, Hayabusa future, Gnomz007, Pilatus, Worldtraveller, Aude, Shanes, Tom, Mavhc, Remember, Art LaPella, Cacophony, Femto, Thunderbrand, Jpgordon, Iridia, Adambro,
Marco Castellani, Causa sui, Bobo192, Circeus, NetBot, Longhair, Hurricane111, Apollo2011, Smalljim, Dreish, Olve Utne, Elipongo,
I9Q79oL78KiL0QTFHgyc, Sasquatch, MrInitialMan, BillCook, Maxl, Pharos, Gsklee, Kvaks, Xen0phile, Vesal, Cyrloc, Storm Rider,
Bob rulz, Alansohn, JYolkowski, Anthony Appleyard, SnowFire, Chris16447, Polarscribe, Borisblue, Atlant, Keenan Pepper, Andrew
Gray, Riana, AzaToth, Yamla, Axl, Lightdarkness, Mailer diablo, InShaneee, Dark Shikari, Mysdaao, Malo, VladimirKorablin, Bart133,
Snowolf, Radical Mallard, Keepsleeping, Crobzub, Suruena, Luspari, Evil Monkey, Harej, Tony Sidaway, Inge-Lyubov, Mikeo, Itsmine,
Versageek, Gene Nygaard, HenryLi, Kazvorpal, WilliamKF, Novacatz, Kelly Martin, Rorschach, Jeffrey O. Gustafson, OwenX, Georgia
guy, Ugo, Benhocking, TomTheHand, BillC, Kzollman, Commander Keane, MONGO, Kelisi, Schzmo, Sengkang, Red Dalek, Eyreland,
Prashanthns, Alec Connors, Smartech, Rnt20, Graham87, Marskell, Deltabeignet, Magister Mathematicae, BD2412, FreplySpang, RxS,
MechanicallySeparatedChicken, NebY, BorgHunter, Pentawing, Sjakkalle, Rjwilmsi, Koavf, Joffan, Urbane Legend, Rillian, BlueMoonlet, Tangotango, Sdornan, Tawker, Mentality, Mike s, Mike Peel, Sajad.Ghafarzadeh, Kazrak, Tewilliams, Ligulem, Bhadani, Ttwaring,
Kaktuse, Knave7, Ucucha, Maurog, Jbamb, Sango123, Yamamoto Ichiro, N0YKG, Roo60, Titoxd, Sugury, Goclenius, FlaBot, Washington Irving, Akiss, RobertG, Old Moonraker, Nihiltres, Nivix, RexNL, Gurch, ChongDae, Arctic.gnome, DannyZ, Str1977, TeaDrinker,
Joedeshon, Srleffler, Jester92, King of Hearts, Chobot, Flying Jazz, ChiTrek, Gwernol, EamonnPKeane, The Rambling Man, YurikBot,
RobotE, Sceptre, Vlad4599, Anonymous editor, Teneyesone, Bergsten, SpuriousQ, CanadianCaesar, Hellbus, Ori.livneh, Stephenb, Rintrah, Polluxian, Mike Young, Merlincooper, Kimchi.sg, Wimt, Lusanaherandraton, NawlinWiki, Bulbabean, Wiki alf, Deskana, Jaxl,
Kvn8907, Mmccalpin, Harksaw, Howcheng, FFLaguna, Dureo, Lexicon, Nick, Retired username, Jamesd, Brandon, Chal7ds, Raven4x4x,
Lomn, Zwobot, Ospalh, T, WMarsh, Bota47, Darkfred, Wknight94, Ms2ger, Virtuini, Tuckerresearch, FF2010, TheSeer, 21655, Poppy,
Zzuuzz, Ufpncc1965, Chesnok, Kandrey89, Ageekgal, Chaos syndrome, Richard s, Theda, Fang Aili, Pb30, Th1rt3en, Opes, Chris
Brennan, Mastercampbell, Aeon1006, Kier07, Hurricane Devon, Rocketrye12, Emc2, ArielGold, RunOrDie, Bly1993, Kungfuadam,
Maxamegalon2000, Paul Erik, Gmrepoli, GrinBot, Iago Dali, Rehevkor, Hawkeyef, SkerHawx, Serendipodous, Victor falk, Caponer,
Deuar, Sardanaphalus, Sintonak.X, A bit iffy, SmackBot, Espresso Addict, Saravask, Bobet, Cdogsimmons, Prodego, KnowledgeOfSelf, Royalguard11, VigilancePrime, Alex1011, Gnangarra, Unyoyega, Pgk, Phaldo, Jacek Kendysz, Kilo-Lima, Bmearns, EncycloPetey,
BPK2, Delldot, Ribbet32, LuciferMorgan, Veesicle, ZeroEgo, Sedonaarizona, Edgar181, Shai-kun, Commander Keane bot, Xaosflux,
Aksi great, Richmeister, Gilliam, Hmains, Ghosts&empties, Skizzik, Superpig56, Saros136, CanbekEsen, Bluebot, Kurykh, Philosopher,
Geneb1955, Dr bab, Mokwella, Rick7425, Silly rabbit, SchfiftyThree, Hibernian, Moshe Constantine Hassan Al-Silverburg, Vanessadannenberg, Dlohcierekim's sock, Wrxsti fan, DHN-bot, [email protected], Mkamensek, Gracenotes, Reaper X, JohnWhitlock,
Zsinj, Can't sleep, clown will eat me, Mrwuggs, LC Revelation, Astringer, Astrobhadauria, Thisisbossi, Chan Yin Keen, Jackmitchell,
Krsont, Addshore, Edivorce, Monacat, Nasty Dick, Krich, PrometheusX303, Cybercobra, Nakon, Jiddisch, J450NH3,“alyosha”, Dreadstar, Astroview120mm, Illnab1024, DMacks, Drc79, Zonk43, Kotjze, Gruznov, N Shar, Zedall, Noobycheese, Risker, Jtm71, Vina-iwbot,
Pilotguy, Kukini, SashatoBot, Esrever, CFLeon, Rory096, Erimus, Harryboyles, Srikeit, Dbtfz, Vanished user 9i39j3, Kuru, John, Drahcir,
Buchanan-Hermit, Moleskin, JohnCub, Mrlopez2681, Sir Nicholas de Mimsy-Porpington, Linnell, Shadowlynk, JoshuaZ, JorisvS, Temple, JayMan, Mgiganteus1, Goodnightmush, Kistler91, Mr. Lefty, IronGargoyle, Jess Mars, Keber, Retromaniac, Ckatz, RandomCritic,
A. Parrot, Slakr, Kyoko, Feureau, Waggers, SandyGeorgia, Funnybunny, Dhp1080, Ryulong, TPIRFanSteve, Gazjo, RichardF, Elb2000,
Jose77, Nakedcellist, 96hixjoh01, Wwagner, Soxrock, ThuranX, Esoltas, Ossipewsk, ILovePlankton, K, Michaelbusch, Dekaels, The Giant Puffin, Joseph Solis in Australia, LandruBek, Newone, Gheuf, KsprayDad, Tony Fox, Richard75, Blehfu, Shikyo2, Az1568, Yoyopro5, Tawkerbot2, Dlohcierekim, Poolkris, Merryjman, Ioannes Pragensis, JForget, Thedemonhog, SpaceHouse, CmdrObot, Geremia,
Robin Scagell, Dycedarg, Scohoust, Makeemlighter, SupaStarGirl, SaintCahier, Vyznev Xnebara, Rwflammang, Drinibot, Ruslik0, Benwildeboer, Juhachi, Outriggr, MarsRover, WeggeBot, Logical2u, Avillia, Tex, RagingR2, Ufviper, AndrewHowse, Cydebot, Stebbins,
Natasha2006, IvarSnaaijer, Nbound, Ryan, Metacosm, -S TANK-, Dominicanpapi82, DrunkenSmurf, SyntaxError55, Gogo Dodo, JFreeman, Flowerpotman, Corpx, ST47, Pgk4, Wikipediarules2221, Caliga10, Tawkerbot4, Christian75, Codetiger, DumbBOT, Chrislk02,
Gonzo fan2007, Voldemortuet, UV, ‫הסרפד‬, Rab V, Casliber, Thijs!bot, LeeG, Davidelit, Volucris, Keraunos, Andyjsmith, Headbomb,
LordKrishna, Marek69, WillMak050389, James086, Yettie0711, Lars Lindberg Christensen, Davidhorman, The Proffesor, AgentPeppermint, Blathnaid, RaNdOm26, Natalie Erin, Lamy999, Escarbot, Mentifisto, Porqin, AntiVandalBot, Yupik, Khing, AbstractClass, Majorly, Gamedude41, Luna Santin, Jmsevits, Ricnun, Nugget-92, Opelio, DragonBlazer57, Exteray, Podolakj, Dr. Submillimeter, Diver
dude2, DarthShrine, Spouima, SkoreKeep, Firiun, Cbrodersen, Myanw, PresN, Gökhan, Kariteh, DOSGuy, JAnDbot, Deflective, Husond,
PopsHunsinger, Mikerobe007, Barek, MER-C, BlindEagle, Planetary, Something14, Hello32020, ThanosMadTitan23, Andonic, Dcooper,
Igodard, Natureguy1980, Roleplayer, Hut 8.5, 100110100, Rentaferret, Savant13, Dermann69, Kirrages, Rothorpe, LittleOldMe, .anacondabot, Acroterion, SteveSims, Bencherlite, Achero, Meeples, Pablothegreat85, Magioladitis, WolfmanSF, Murgh, Bongwarrior, VoABot II,
AuburnPilot, Wikidudeman, MJD86, Davidjk, Hasek is the best, Frip1000, Mbc362, ‫باسم‬, Rivertorch, Bigdan201, CTF83!, Jonte-, I ain't JtV, SparrowsWing, Midgrid, Indon, Animum, Cyktsui, ArthurWeasley, Allstarecho, Styrofoam1994, Mike Payne, Chris103,
St.Jimmy666, Shijualex, Just James, Denmer, DerHexer, JaGa, Megalodon99, Lelkesa, Strider01, Doesper, Lost tourist, Revcph1958,
Spacew00t, Kheider, PsyMar, Soderpoppers, Hdt83, MartinBot, FlieGerFaUstMe262, Tooter Shellby, BetBot, Ben MacDui, Rettetast,
Ravichandar84, Ambi Valent, CommonsDelinker, AlexiusHoratius, Bgold4, Lilac Soul, Ducksauce101, Trew.Trew, Dinkytown, Kathlyn.Price, Nerablade, AlphaEta, Jameswheeler, Watch37264, J.delanoy, DrKiernan, Nate1028, Skeptic2, AstroHurricane001, AAA!,
Lizrael, BillWSmithJr, Think777, Hans Dunkelberg, Piercetheorganist, All Is One, Jameswheeleratskool, Nigholith, Eliz81, MogWV,
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Sirkad, Psyche825, Seb az86556, Cremepuff222, Jmpenzone, Ranger1524, Onore Baka Sama, Maxim, Damërung, Orange-kun, Knightshield, Jclarine, MooCowWow, Mikeandrich, Pious7, Lerdthenerd, Enigmaman, Josehunder, Constantine Gorov, Masterchi101, Haloiscool, Lerolock, Synthebot, Novena, SmileToday, Falcon8765, Burntsauce, Osimi11, Coltman61, Zach21, Coopol, Bungo77, Spriteddude,
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7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES
125
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Nicolas Eynaud, AvicAWB, H3llBot, Rapture2018, Kyucasio, 3sdanog, Мл.научный сотрудник, L Kensington, Jguy, Jrichard2012,
Spartylove, Sailsbystars, Lewis274, Puffin, Chinoblanco, Smartie2thaMaxXx, CGPGrey, Honesty First, ChuispastonBot, Ryanmagoo,
Terra Novus, Whoop whoop pull up, Alcazar84, Dmp99, ClueBot NG, AlbertBickford, Brett2829, Derschmidt, Frietjes, Delusion23,
Corusant, Kirklove, Castncoot, Helpful Pixie Bot, Msd2001, Gob Lofa, Bibcode Bot, Symbiboy, MKar, Ableblood, SpaceChimp1992,
Gallina3795, Dotdotdotatsignapostrophe, Q6637p, Cadiomals, Denassq, Tycho Magnetic Anomaly-1, Colinmartin74, Louissegal2000,
Wavyinfinity, Thanhtinsaosang, SoylentPurple, Bumbo1234, Rhlozier, Ekren, Dexbot, Br'er Rabbit, Blobbie244, Clockery, CorinneSD,
JustAMuggle, Reatlas, Rfassbind, MarchOrDie, Epicgenius, Jcpag2012, Lindenhurst Liberty, B14709, SamX, 展翅飛翔, Transphasic,
Thedrumsmasher, OccultZone, Jomey, Cancina5645, PlayStation 14, Monkbot, SkateTier, Trackteur, EricAnthony101, Spiderjerky, Tetra
quark, Sol2y and Anonymous: 1234
• Venus Source: http://en.wikipedia.org/wiki/Venus?oldid=655942758 Contributors: NathanBeach, Brion VIBBER, Eloquence, Vicki
Rosenzweig, Mav, Bryan Derksen, Zundark, The Anome, Taw, Jeronimo, Malcolm Farmer, -- April, Mark, Ed Poor, Aidan ElliottMcCrea, Amillar, Alex.tan, Andre Engels, Eob, Danny, XJaM, JeLuF, William Avery, SimonP, GrahamN, Fonzy, Dwheeler, Olivier,
Rickyrab, Fransvannes, Rbrwr, Spiff, Seldon, Edward, Patrick, Infrogmation, Ken Arromdee, Michael Hardy, Tim Starling, Oliver Pereira,
Lexor, Nixdorf, Ixfd64, Tango, Cyde, Minesweeper, Alfio, Kosebamse, Shimmin, Egil, Looxix, Ihcoyc, Mdebets, Ahoerstemeier, Snoyes,
CatherineMunro, TUF-KAT, TUF-KAT, Angela, Mark Foskey, Glenn, Poor Yorick, Kwekubo, Evercat, Lancevortex, Mxn, Raven in Orbit,
Schneelocke, Hike395, Hashar, Timwi, RickK, Stone, Andrewman327, Doradus, Haukurth, CBDunkerson, Robertb-dc, Tpbradbury, Dragons flight, Furrykef, Taxman, Ringomassa, Head, Samsara, Traroth, Anupamsr, Bloodshedder, Raul654, Wetman, BenRG, Jeffq, Owen,
Lumos3, Phil Boswell, Robbot, MrJones, Celsius1414, Naddy, Modulatum, Smallweed, Chris Roy, Merovingian, Academic Challenger,
Rursus, Geogre, Bkell, Hadal, UtherSRG, Wereon, Anthony, Peter L, Carnildo, ShutterBugTrekker, Nephelin, Centrx, Giftlite, Reubenbarton, Christopher Parham, Djinn112, Awolf002, Jyril, Sj, TOttenville8, Harp, Nichalp, Wolfkeeper, Tom harrison, Lupin, Herbee, Karn,
Alterego, Everyking, Curps, Michael Devore, Henry Flower, Wikibob, Jackbrown, Joe Kress, Erdal Ronahi, Sdfisher, Gareth Wyn, Kainaw,
Rchandra, Gzornenplatz, Matt Crypto, Python eggs, Jackol, Bobblewik, Cam, Wmahan, Infinitysnake, OldakQuill, ChicXulub, Gadfium,
Andycjp, DocSigma, Alexf, Geni, Xmnemonic, Chris Edgemon, Yath, Antandrus, The Singing Badger, HorsePunchKid, Zaha, MisfitToys,
Piotrus, Vanished user 1234567890, Kusunose, FelineAvenger, Rdsmith4, Samy Merchi, RetiredUser2, Tomruen, Icairns, B.d.mills, Neutrality, Urhixidur, Edsanville, Irpen, Ukexpat, Fg2, JohnArmagh, Deglr6328, Chmod007, M1ss1ontomars2k4, Marnevell, Lacrimosus,
Spiffy sperry, DanielCD, Ultratomio, EugeneZelenko, Indosauros, Mark Zinthefer, Discospinster, Rich Farmbrough, Avriette, Guanabot,
BlueMars, Supercoop, FraKctured, Martin TB, Vsmith, Florian Blaschke, ArnoldReinhold, Rasmusdf, Ponder, D-Notice, Dbachmann,
Mani1, Chrislee, MuDavid, Pavel Vozenilek, SpaceFrog, Bender235, NeilTarrant, Violetriga, Evice, Brian0918, RJHall, Ylee, Sfahey, El
C, Fenevad, Huntster, Joanjoc, Kwamikagami, Evand, Worldtraveller, Tverbeek, Remember, Art LaPella, Femto, Adambro, Bobo192,
Circeus, Smalljim, NightDragon, .:Ajvol:., ZayZayEM, Elipongo, Angie Y., Nesnad, Kappa, La goutte de pluie, Jojit fb, Timsheridan,
BillCook, Sam Korn, Fwb22, Gsklee, A2Kafir, Jumbuck, Danski14, Bob rulz, Alansohn, Gary, Tablizer, Eric Kvaalen, Keenan Pepper,
Moanzhu, Andrewpmk, Paleorthid, Andrew Gray, Sp82, Cbotman, AzaToth, Lectonar, Corwin8, JanSöderback, Mlm42, Hu, Avenue,
DreamGuy, Snowolf, Mbloore, Velella, BanyanTree, Juan Toledo, Rebroad, Evil Monkey, RainbowOfLight, Inge-Lyubov, Cmapm, Zxcvbnm, Gene Nygaard, Dan East, HenryLi, Tr00st, Leopard, Red dwarf, Adrian.benko, BerserkerBen, Duke33, Feezo, Siafu, Gmaxwell,
WilliamKF, Angr, Rorschach, Mel Etitis, Woohookitty, Jannex, DonPMitchell, ChrisNoe, TigerShark, Ylem, MrNexx, Volcanopele, Decrease789, Plek, BillC, Bigfrozenhead, Chris Mason, Zealander, Bricktop, Nefertum17, MONGO, Eleassar777, Pi@k, Tabletop, Keta,
Kelisi, Ch'marr, TotoBaggins, BartBenjamin, Cat11, Steinbach, X444, Sengkang, GregorB, CharlesC, Jon Harald Søby, Mayz, Oldelpaso, Prashanthns, Smartech, Teemu Leisti, Driftwoodzebulin, Cataclysm, Emerson7, MrSomeone, Paxsimius, Mandarax, Ashmoo, Graham87, Marskell, JiMidnite, Johnny Mnemonic, Deltabeignet, Magister Mathematicae, TAKASUGI Shinji, FreplySpang, RxS, Pentawing,
Jcmo, Canderson7, Funkymuskrat, Drbogdan, Akubhai, Rjwilmsi, Urbane Legend, Vary, Hiberniantears, JoshuacUK, Tawker, Mentality,
Heah, Mike Peel, Crazynas, Bubba73, Boccobrock, AndyKali, Brighterorange, Afterwriting, Ttwaring, Wkruse, GregAsche, Sango123,
DirkvdM, Dbigwood, Yamamoto Ichiro, FayssalF, Titoxd, Ian Pitchford, SchuminWeb, RobertG, Crazycomputers, Finsen, Nivix, RexNL,
Gurch, Arctic.gnome, Enon, R Lee E, TeaDrinker, Alphachimp, Malhonen, Srleffler, DybrarH, Zotel, Gurubrahma, Glenn L, Kelpi,
Phoenix2, King of Hearts, Chobot, Raincheerleader, Rewster, DVdm, PainMan, Mysekurity, Debivort, Cobaahema, Banaticus, Elfguy,
Roboto de Ajvol, The Rambling Man, Satanael, Mercury McKinnon, TexasAndroid, Koveras, Deeptrivia, Jimp, RussBot, Kauffner, Fabar-
126
CHAPTER 7. VENUS
tus, Anonymous editor, Gspr, Witan, Qrasy, Hydrargyrum, Stephenb, Mithridates, Gaius Cornelius, CambridgeBayWeather, Cpuwhiz11,
Kimchi.sg, Dorthonion, Bovineone, Wimt, Ebow, Anomalocaris, NawlinWiki, SEWilcoBot, Wiki alf, BGManofID, Itisan, Exir Kamalabadi, RazorICE, Seegoon, Bmdavll, Irishguy, Brandon, Dppowell, Rmky87, Raven4x4x, Semperf, Tony1, Martinwilke1980, Wknight94,
Noosfractal, Leptictidium, Manjithkaini, Bdell555, Mike Serfas, Show no mercy, 21655, Deville, Twintop, Zzuuzz, Chase me ladies,
I'm the Cavalry, Closedmouth, Rpvdk, Pb30, KGasso, Acer, Shakil Mustafa, JoanneB, Symon, Fram, Hurricane Devon, Geoffrey.landis,
HereToHelp, Kaippally, Wbrameld, Nixer, RunOrDie, Kungfuadam, Junglecat, Phr en, Iago Dali, Serendipodous, DVD R W, Caponer,
Luk, Rayd8, Deuar, IslandHopper973, Sardanaphalus, Veinor, Sintonak.X, SmackBot, Mark Tranchant, KnowledgeOfSelf, Hydrogen Iodide, Dodava, Lsorin, Jagged 85, Davewild, Thunderboltz, WookieInHeat, EncycloPetey, Jrockley, Jab843, Mdd4696, Lotse, ProveIt,
Canthusus, TheDoctor10, Timsbleung, HalfShadow, JFHJr, PeterSymonds, Ema Zee, Gilliam, DividedByNegativeZero, Oscarthecat,
Skizzik, Saros136, Amatulic, Master Jay, Keegan, JonRidinger, Geneb1955, Agateller, Quinsareth, Persian Poet Gal, Jlao04, Northern,
Cbh, Anchoress, Hollow Wilerding, SchfiftyThree, Hibernian, No-Bullet, Ikiroid, Ctbolt, Baa, DHN-bot, [email protected],
Sbharris, Darth Panda, Lewis007, Scwlong, Salmar, Can't sleep, clown will eat me, VJDocherty, DHeyward, Murder1, Mrwuggs, Astrobhadauria, Wikipedia brown, Krsont, Andy120290, Addshore, Kcordina, Edivorce, Rocksandfossils, Aldaron, Krich, Robma, Nakon,
TMW, Dreadstar, Wjtimmerman, Mini-Geek, Hgilbert, Jan.Kamenicek, Polonium, Omnipotence, Adrigon, SpiderJon, MonkeyMumford,
Zonk43, Risker, Ck lostsword, FelisLeo, NeilFraser, Sarfa, Ohconfucius, GoldenTorc, Thejerm, SashatoBot, Mksword, NormalGoddess,
Kuru, Titus III, John, JanderVK, Drahcir, Jrothwell, Soumyasch, Linnell, JoshuaZ, Kreuzfeld, JorisvS, Temple, Scetoaux, IronGargoyle,
SpyMagician, Jess Mars, Keber, Heliogabulus, Chrisd87, Ckatz, The Man in Question, RandomCritic, A. Parrot, Serpentinite, Beetstra,
Stevebritgimp, Jhpace1, George The Dragon, Xiaphias, Don Alessandro, Tobyw87, Kliqjaw, Ryulong, Sims2789, RichardF, Novangelis,
Elb2000, Jose77, Peyre, Floridan, Politepunk, Papertiger, BranStark, Iridescent, Majorbonkers, Michaelbusch, Alessandro57, Scooter20,
Newone, J Di, Igoldste, Takarada, CapitalR, Ewulp, Mssgill, Tawkerbot2, Dlohcierekim, George100, Poolkris, Arhain, P-Chan, CalebNoble, Sarvagnya, Vjamesv, Gustavh, JForget, Adam Keller, VoxLuna, CmdrObot, Ale jrb, Geremia, TheHerbalGerbil, Memetics, Sasho84,
Tuvas, BeenAroundAWhile, N3X15, Runningonbrains, MiShogun, BKalesti, Ruslik0, GHe, Orannis, CuriousEric, Dwolsten, MarsRover,
Todowd, Joelholdsworth, WeggeBot, Moreschi, Borislav Dopudja, Nilfanion, Ufviper, Rudjek, Schauf, Icek, Badseed, Nbound, Dominicanpapi82, ArgentTurquoise, Steel, DrunkenSmurf, Vanished user vjhsduheuiui4t5hjri, Gogo Dodo, Red Director, Zginder, MattButts,
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W, Paddles, Asenine, Robertinventor, Thenewestdoctorwho, Brad101, SteveMcCluskey, Sancort, Omicronpersei8, Cancun771, Theirishpianist, Maat333, OakAve222, FrancoGG, Thijs!bot, Epbr123, Tepidpond, Interested2, Cassie, cole, Keraunos, Andyjsmith, Anthius,
Halibut Thyme, Headbomb, Newton2, Ranger 1 (usurped), A3RO, HelenKMarks, Brichcja, Catsmoke, DoomsDay349, Grayshi, Nick
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outside the box, Stotan, Lucyin, Bigdan201, Avicennasis, Wikiwhat?, Catgut, Panser Born, Spookiejjr, Cyktsui, ArthurWeasley, Arbeiter,
Torchiest, 28421u2232nfenfcenc, BilCat, Joeloveslego, Jc1346729, MorningGrace, IanUK, AdoreMila, Just James, Glen, DerHexer, JaGa,
Megalodon99, TheRanger, Markco1, Kheider, Gjd001, Oren0, Bmf 51, Cliff smith, Hdt83, MartinBot, Schmloof, FlieGerFaUstMe262,
PAK Man, PatrickLMT, Vlink, Theodore141, Jim.henderson, Naohiro19, Rettetast, Jerry teps, Uriel8, R'n'B, CommonsDelinker, AlexiusHoratius, Genesis12, Paranomia, Watch37264, J.delanoy, Pharaoh of the Wizards, Tinwelint, DrKiernan, Bogey97, DomBot, 16345,
Uncle Dick, All Is One, Jameswheeleratskool, Mike.lifeguard, KrytenKoro, Anoushirvan, WarthogDemon, Thaurisil, Nemrac2, ABTU,
Rod57, IdLoveOne, Vegasprof, Bot-Schafter, Katalaveno, McSly, Vandriel1325, Vineeth.vooppala, DJ1AM, Gurchzilla, Jancoop, (jarbarf), M-le-mot-dit, Mortbrew, WHeimbigner, NewEnglandYankee, Rominandreu, Fountains of Bryn Mawr, Gallador, Supersmell, SJP,
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Toddst1, Meh123123, Tiptoety, Radon210, Oda Mari, Arbor to SJ, Metroidhunterx, Travis Evans, Zfaith, Gublefink, Phantasystar000,
Wombatcat, Prestonmag, Mimihitam, OsamaBinLogin, Jdl108, Oxymoron83, Antonio Lopez, Nuttycoconut, RMB1987, Steven Zhang,
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BenTrotsky, Mentisock, LaaknorBot, Huntyou3, Pirate Kitten, Computermonitor, Redheylin, 37ophiuchi, Nick9902, Ld100, Debresser,
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License: Public domain Contributors: http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20040311a.html (Raw image at http://
marsrovers.jpl.nasa.gov/gallery/all/1/p/045/1P132176262ESF05A6P2670R8M1.HTML) Original artist: NASA/JPL/Cornell
• File:391243main-MarsRover-ShelterIslandMeteorite-20091002-crop.jpg Source: http://upload.wikimedia.org/wikipedia/commons/
a/a2/391243main-MarsRover-ShelterIslandMeteorite-20091002-crop.jpg License: Public domain Contributors: http://www.nasa.gov/
images/content/391243main_mer20091002-full.jpg Original artist: NASA/JPL-Caltech
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• File:Comet-C2013A1-SidingSpring-NearMars-Hubble-20141019.jpg Source: http://upload.wikimedia.org/wikipedia/commons/e/
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• File:Comet-SidingSpring-Passing-PlanetMars-On-20141019-ArtistConcept-20140905.jpg Source: http://upload.wikimedia.org/
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• File:CometSidingSpring-HeadingTowardsMars-ArtistConcept-20141006.jpg Source:
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• File:Commons-logo.svg Source: http://upload.wikimedia.org/wikipedia/en/4/4a/Commons-logo.svg License: ? Contributors: ? Original
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• File:Conjunction_of_Jupiter_and_Moon.jpg Source:
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• File:Deimos-MRO.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/8d/Deimos-MRO.jpg License: Public domain Contributors: http://marsprogram.jpl.nasa.gov/mro/gallery/press/20090309a.html Original artist: NASA/JPL-caltech/University of Arizona
• File:Different_Faces_Neptune.jpg Source:
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? Original artist: ?
• File:ESO_-_Uranus_(by).jpg Source: http://upload.wikimedia.org/wikipedia/commons/4/44/ESO_-_Uranus_%28by%29.jpg License:
CC BY 4.0 Contributors: Peering at Uranus's Rings as they Swing Edge-on to Earth for the First Time Since their Discovery in 1977
Original artist: ESO
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• File:Earth-Moon_system_as_seen_from_Saturn_(PIA17171).jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/32/
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• File:Enceladus_geysers.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/0e/Enceladus_geysers.jpg License: Public domain Contributors: http://www.jpl.nasa.gov/news/news.cfm?release=2010-061&cid=release_2010-061&msource=n20100223&tr=y&
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• File:Europa-moon.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/54/Europa-moon.jpg License: Public domain Contributors: ? Original artist: ?
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• File:Hs-2009-23-crop.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/89/Hs-2009-23-crop.jpg License: Public domain
Contributors: Cropped from Hubblesite (STScI-2009-23) Original artist: Credit: NASA, ESA, and H. Hammel (Space Science Institute,
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• File:Hubble_sees_a_flickering_light_display_on_Saturn.jpg Source:
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• File:Jupiter-bonatti.png Source: http://upload.wikimedia.org/wikipedia/commons/c/cb/Jupiter-bonatti.png License: Public domain
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• File:Jupiter.Aurora.HST.UV.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/8e/Jupiter.Aurora.HST.UV.jpg License:
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ap001219.html Original artist: John T. Clarke (University of Michigan), ESA, NASA
• File:Jupiter_MAD.jpg Source: http://upload.wikimedia.org/wikipedia/commons/7/70/Jupiter_MAD.jpg License: CC BY 4.0 Contributors: http://www.eso.org/public/outreach/press-rel/pr-2008/images/phot-33-08-fullres.jpg Originally uploaded 16:14, 19 November 2008
(UTC) by Lars Lindberg Christensen (talk • contribs) to en:wiki. Original artist: ESO/F. Marchis, M. Wong, E. Marchetti, P. Amico, S.
Tordo
• File:Jupiter_New_Horizons.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/c1/Jupiter_New_Horizons.jpg License:
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PNG images, downscaled to half size, then converted at maximum quality (10) and each frame forced to be a keyframe using programs
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mission_pages/cassini/multimedia/pia08332.html Original artist: NASA
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Space Science Systems
• File:Mgn_p39146.png Source: http://upload.wikimedia.org/wikipedia/commons/b/bb/Mgn_p39146.png License: Public domain Contributors: ? Original artist: ?
• File:Msl20110526_MSL_Artist_Concept_PIA14164-full.jpg Source:
http://upload.wikimedia.org/wikipedia/commons/2/27/
Msl20110526_MSL_Artist_Concept_PIA14164-full.jpg License: Public domain Contributors: http://marsprogram.jpl.nasa.gov/msl/
multimedia/images/?ImageID=3511 Original artist: NASA
• File:NASA-14090-Comet-C2013A1-SidingSpring-Hubble-20140311.jpg Source: http://upload.wikimedia.org/wikipedia/commons/
a/ac/NASA-14090-Comet-C2013A1-SidingSpring-Hubble-20140311.jpg License: Public domain Contributors: http://www.nasa.gov/
sites/default/files/14-090-hubble-comet_0.jpg Original artist: NASA, ESA, and J.-Y. Li (Planetary Science Institute)
• File:NASA-Cassini-Saturn-TitanFlybyTests-20140617.jpg
Source:
http://upload.wikimedia.org/wikipedia/commons/3/3a/
NASA-Cassini-Saturn-TitanFlybyTests-20140617.jpg License: Public domain Contributors: http://www.jpl.nasa.gov/images/cassini/
20140617/cassini20140617-full.jpg Original artist: NASA/JPL-Caltech
• File:NASA-MarsRock-Yogi-SuperRes.jpg
NASA-MarsRock-Yogi-SuperRes.jpg License:
Original artist: NASA/JPL/Dr. Timothy Parker
Source:
http://upload.wikimedia.org/wikipedia/commons/c/c4/
Public domain Contributors: http://mars.jpl.nasa.gov/MPF/ops/Yogi_super_res.jpg
• File:NASA14135-Jupiter-GreatRedSpot-Shrinks-20140515.jpg Source:
http://upload.wikimedia.org/wikipedia/commons/3/30/
NASA14135-Jupiter-GreatRedSpot-Shrinks-20140515.jpg License: Public domain Contributors: http://www.nasa.gov/sites/default/
files/14-135-jupiter2_0.jpg Original artist: NASA, ESA, and A. Simon (Goddard Space Flight Center)
• File:NASA_Curiosity_rover_-_Link_to_a_Watery_Past_(692149main_Williams-2pia16188-43).jpg
Source:
http:
//upload.wikimedia.org/wikipedia/commons/7/79/NASA_Curiosity_rover_-_Link_to_a_Watery_Past_%28692149main_
Williams-2pia16188-43%29.jpg License: Public domain Contributors: Link to a Watery Past Original artist: NASA/JPL-Caltech/MSSS
• File:Nasa_mars_opportunity_rock_water_150_eng_02mar04.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/29/
Nasa_mars_opportunity_rock_water_150_eng_02mar04.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/
catalog/pia05474 Original artist: NASA/JPL/US Geological Survey
• File:Neptune'{}s_Great_Dark_Spot.jpg Source: http://upload.wikimedia.org/wikipedia/commons/d/df/Neptune%27s_Great_Dark_
Spot.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA00052 Original artist: NASA / Jet Propulsion
Lab
• File:Neptune,_Earth_size_comparison.jpg Source: http://upload.wikimedia.org/wikipedia/commons/d/d5/Neptune%2C_Earth_size_
comparison.jpg License: Public domain Contributors: This image was made from NASA Earth America 2010.jpg and Neptune Full.jpg
Original artist: ?
• File:Neptune-Methane.jpg Source: http://upload.wikimedia.org/wikipedia/commons/6/6a/Neptune-Methane.jpg License: Public domain Contributors: frame from video on Hubblesite: STScI-2005-22 Original artist: Hubble Space Telescope
• File:Neptune-visible.jpg Source: http://upload.wikimedia.org/wikipedia/commons/6/63/Neptune-visible.jpg License: Public domain
Contributors: ? Original artist: ?
• File:Neptune_Full.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/56/Neptune_Full.jpg License: Public domain Contributors: JPL image Original artist: NASA
• File:Neptune_Orbit.gif Source: http://upload.wikimedia.org/wikipedia/commons/6/66/Neptune_Orbit.gif License: CC BY-SA 3.0 Contributors: Own work Original artist: Lookang many thanks to author of original simulation = Todd K. Timberlake author of Easy Java
Simulation = Francisco Esquembre
• File:Neptune_clouds.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/c8/Neptune_clouds.jpg License: Public domain
Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA00058 Original artist: NASA / Jet Propulsion Lab
• File:Neptune_diagram.svg Source: http://upload.wikimedia.org/wikipedia/commons/f/fd/Neptune_diagram.svg License: CC BY-SA
3.0 Contributors: http://solarsystem.nasa.gov/multimedia/gallery/Neptune_Int-browse.jpg, which is in the public domain Original artist:
NASA; Pbroks13 (redraw)
• File:Neptune_storms.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/8c/Neptune_storms.jpg License: Public domain
Contributors: http://antwrp.gsfc.nasa.gov/apod/ap010821.html Original artist: NASA/Voyager 2 Team
• File:Neptune_symbol.svg Source: http://upload.wikimedia.org/wikipedia/commons/4/47/Neptune_symbol.svg License: Public domain
Contributors: Own work Original artist: Amit6
• File:Neptunerings.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/87/Neptunerings.jpg License: Public domain Contributors: Transferred from en.wikipedia; transfer was stated to be made by User:Cocu. Original artist: Original uploader was Serendipodous
at en.wikipedia
7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES
131
• File:Office-book.svg Source: http://upload.wikimedia.org/wikipedia/commons/a/a8/Office-book.svg License: Public domain Contributors: This and myself. Original artist: Chris Down/Tango project
• File:Olympus_Mons_alt.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/00/Olympus_Mons_alt.jpg License: Public domain Contributors: Edited version of File:Olympus Mons.jpg originally from http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-mars.
html#features. Original artist: Image by NASA, modifications by Seddon
• File:Orbits_of_Phobos_and_Deimos.gif Source:
http://upload.wikimedia.org/wikipedia/commons/d/db/Orbits_of_Phobos_and_
Deimos.gif License: CC BY-SA 2.5 Contributors: ? Original artist: ?
• File:P11saturnb.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/c7/P11saturnb.jpg License: Public domain Contributors:
? Original artist: ?
• File:PIA00819left-MarsRock-BarnacleBill.gif
Source:
http://upload.wikimedia.org/wikipedia/commons/2/2f/
PIA00819left-MarsRock-BarnacleBill.gif License: Public domain Contributors: http://photojournal.jpl.nasa.gov/figures/PIA00819left.gif
Original artist: NASA/JPL
• File:PIA01482_Saturn_Montage.jpg Source: http://upload.wikimedia.org/wikipedia/commons/7/7d/PIA01482_Saturn_Montage.jpg
License: Public domain Contributors: JPL image PIA01482 Original artist: NASA
• File:PIA01627_Ringe.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/29/PIA01627_Ringe.jpg License: Public domain
Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA01627 Original artist: NASA/JPL/Cornell University
• File:PIA02863_-_Jupiter_surface_motion_animation_thumbnail_300px_10fps.ogv
Source:
http://upload.wikimedia.org/
wikipedia/commons/6/68/PIA02863_-_Jupiter_surface_motion_animation_thumbnail_300px_10fps.ogv License:
Public domain
Contributors: http://photojournal.jpl.nasa.gov/archive/PIA02863.gif linked from http://photojournal.jpl.nasa.gov/animation/PIA02863,
transcoded and downscaled to a maximum quality (10) Theora video, each frame forced to be a keyframe, using programs MPlayer
for Windows (version 0.6.9+SVN-r3532 using Qt 4.6.2 using MPlayer SVN r31170) and png2theora (version 1.1 binary build from
20100523) as follows: Original artist: NASA/JPL/University of Arizona
• File:PIA02879_-_A_New_Year_for_Jupiter_and_Io.jpg Source: http://upload.wikimedia.org/wikipedia/commons/6/65/PIA02879_
-_A_New_Year_for_Jupiter_and_Io.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA02879 Original artist: NASA/JPL/University of Arizona
• File:PIA05482_modest.jpg Source: http://upload.wikimedia.org/wikipedia/commons/f/fe/PIA05482_modest.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/pia05482 Original artist: NASA/JPL/Cornell
• File:PIA07269-Mars_Rover_Opportunity-Iron_Meteorite.jpg Source:
http://upload.wikimedia.org/wikipedia/commons/6/62/
PIA07269-Mars_Rover_Opportunity-Iron_Meteorite.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/
PIA07269 (TIFF converted into 100% quality JPEG) Original artist: NASA/JPL/Cornell
• File:PIA09089-RA3-hirise-closeup_annotated.png
Source:
http://upload.wikimedia.org/wikipedia/en/d/d3/
PIA09089-RA3-hirise-closeup_annotated.png License: PD Contributors: ? Original artist: ?
• File:PIA13418_-_Oileán_Ruaidh_meteorite_on_Mars_(false_colour).jpg
Source:
http://upload.wikimedia.org/wikipedia/
commons/a/a9/PIA13418_-_Oile%C3%A1n_Ruaidh_meteorite_on_Mars_%28false_colour%29.jpg License: Public domain Contributors: NASA and JPL Original artist: NASA/JPL-Caltech/Cornell University
• File:PIA14762-MarsCuriosityRover-BathurstInletRock.jpg Source:
http://upload.wikimedia.org/wikipedia/commons/1/15/
PIA14762-MarsCuriosityRover-BathurstInletRock.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/jpeg/
PIA14762.jpg Original artist: NASA/JPL-Caltech/Malin Space Science Systems
• File:PIA15038_-_Spirit_lander_and_Bonneville_Crater_on_Mars.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/
1c/PIA15038_-_Spirit_lander_and_Bonneville_Crater_on_Mars.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.
gov/catalog/PIA15038 Original artist: NASA/JPL-Caltech/Univ. of Arizona
• File:PIA16068_-_Mars_Curiosity_Rover_-_Aeolis_Mons_-_20120817.jpg Source:
http://upload.wikimedia.org/wikipedia/
commons/b/bb/PIA16068_-_Mars_Curiosity_Rover_-_Aeolis_Mons_-_20120817.jpg License:
Public domain Contributors:
http://photojournal.jpl.nasa.gov/jpeg/PIA16068.jpg Original artist: NASA/JPL-Caltech/MSSS
• File:PIA16187-MarsCuriosityRover-GoulburnRock-20120817-crop.jpg Source: http://upload.wikimedia.org/wikipedia/commons/
d/d5/PIA16187-MarsCuriosityRover-GoulburnRock-20120817-crop.jpg License: Public domain Contributors: http://www.nasa.gov/
sites/default/files/images/692138main_malin-4pia16187-43_full.jpg Original artist: NASA/JPL-Caltech/MSSS
• File:PIA16192-MarsCuriosityRover-Target-JakeRock-20120927.jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/
3a/PIA16192-MarsCuriosityRover-Target-JakeRock-20120927.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.
gov/catalog/PIA16192 (direct link) Original artist: NASA/JPL-Caltech/MSSS
• File:PIA16239_High-Resolution_Self-Portrait_by_Curiosity_Rover_Arm_Camera.jpg Source:
http://upload.wikimedia.org/
wikipedia/commons/d/dc/PIA16239_High-Resolution_Self-Portrait_by_Curiosity_Rover_Arm_Camera.jpg License: Public domain
Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA16239 Original artist:
• Derivative work including grading, distortion correction, minor local adjustments and rendering from tiff-file: Julian Herzog
• File:PIA16450-MarsDustStorm-20121118.jpg
Source:
http://upload.wikimedia.org/wikipedia/commons/b/b2/
PIA16450-MarsDustStorm-20121118.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/jpeg/PIA16450.jpg
Original artist: NASA/JPL-Caltech/MSSS
• File:PIA16452-MarsCuriosityRover-Rocknest3Rock-20121005.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/b1/
PIA16452-MarsCuriosityRover-Rocknest3Rock-20121005.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/
jpeg/PIA16452.jpg Original artist: NASA/JPL-Caltech/Malin Space Science Systems
• File:PIA16454-MarsDustStorm-20121125.jpg
Source:
http://upload.wikimedia.org/wikipedia/commons/9/9c/
PIA16454-MarsDustStorm-20121125.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/jpeg/PIA16454.jpg
Original artist: NASA/JPL-Caltech/MSSS
132
CHAPTER 7. VENUS
• File:PIA16791-MarsCuriosityRover-Composition-YellowknifeBayRocks.png Source:
http://upload.wikimedia.org/wikipedia/
commons/7/71/PIA16791-MarsCuriosityRover-Composition-YellowknifeBayRocks.png License:
Public domain Contributors:
http://photojournal.jpl.nasa.gov/catalog/PIA16791 Original artist: NASA/JPL-Caltech/University of Guelph
• File:PIA16795-MarsCuriosityRover-TintinaRock-Context-20130119.jpg
Source:
http://upload.wikimedia.org/wikipedia/
commons/3/32/PIA16795-MarsCuriosityRover-TintinaRock-Context-20130119.jpg License:
Public domain Contributors:
http://photojournal.jpl.nasa.gov/jpeg/PIA16795.jpg Original artist: NASA/JPL-Caltech/MSSS
• File:PIA17062-MarsCuriosityRover-HottahRockOutcrop-20120915.jpg Source: http://upload.wikimedia.org/wikipedia/commons/
0/00/PIA17062-MarsCuriosityRover-HottahRockOutcrop-20120915.jpg License: Public domain Contributors: http://photojournal.jpl.
nasa.gov/jpeg/PIA17062.jpg Original artist: NASA/JPL-Caltech/MSSS
• File:PIA17074-MarsOpportunityRover-EsperanceRock-20130223-fig1.jpg Source:
http://upload.wikimedia.org/wikipedia/
commons/2/2d/PIA17074-MarsOpportunityRover-EsperanceRock-20130223-fig1.jpg License:
Public domain Contributors:
http://photojournal.jpl.nasa.gov/catalog/PIA17074 (image link) Original artist: NASA/JPL-Caltech/Cornell Univ./Arizona State
Univ.
• File:PIA18078-PossibleBeginning-NewMoonOfPlanetSaturn-20130415.jpg Source:
http://upload.wikimedia.org/wikipedia/
commons/a/a0/PIA18078-PossibleBeginning-NewMoonOfPlanetSaturn-20130415.jpg License:
Public domain Contributors:
http://photojournal.jpl.nasa.gov/jpeg/PIA18078.jpg Original artist: NASA/JPL-Caltech/Space Science Institute
• File:PIA18274-Saturn-NorthPolarHexagon-Cassini-20140402.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/8e/
PIA18274-Saturn-NorthPolarHexagon-Cassini-20140402.jpg License: Public domain Contributors: http://www.nasa.gov/sites/default/
files/pia18274_full.jpg Original artist: NASA/JPL-Caltech/Space Science Institute
• File:PIA18381-Mars-FreshAsteroidImpact2012-Before27March-After28March.jpg Source:
http://upload.wikimedia.org/
wikipedia/commons/e/e8/PIA18381-Mars-FreshAsteroidImpact2012-Before27March-After28March.jpg License:
Public domain
Contributors: http://photojournal.jpl.nasa.gov/jpeg/PIA18381.jpg Original artist: NASA/JPL-Caltech/MSSS
• File:PIA18611-Mars-CometSidingSpringFlyby-20141009.jpg Source:
http://upload.wikimedia.org/wikipedia/commons/1/12/
PIA18611-Mars-CometSidingSpringFlyby-20141009.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/figures/
PIA18611_fig1.jpg Original artist: NASA/JPL-Caltech
• File:PIA18613-MarsMAVEN-Atmosphere-3UV-Views-20141014.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/
00/PIA18613-MarsMAVEN-Atmosphere-3UV-Views-20141014.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.
gov/jpeg/PIA18613.jpg Original artist: NASA/Univ. of Colorado
• File:PIA19088-MarsCuriosityRover-MethaneSource-20141216.png Source: http://upload.wikimedia.org/wikipedia/commons/6/69/
PIA19088-MarsCuriosityRover-MethaneSource-20141216.png License: Public domain Contributors: http://mars.jpl.nasa.gov/msl/
images/methane-source-mars-rover-curiosity-pia19088-full.jpg Original artist: NASA/JPL-Caltech
• File:People_icon.svg Source: http://upload.wikimedia.org/wikipedia/commons/3/37/People_icon.svg License: CC0 Contributors: OpenClipart Original artist: OpenClipart
• File:Phases-of-Venus.svg Source: http://upload.wikimedia.org/wikipedia/commons/d/d1/Phases-of-Venus.svg License: Public domain
Contributors: Based on PD raster image Image:Phasesofvenus.jpg, http://history.nasa.gov/SP-424/p4.jpg Original artist: Nichalp 09:56,
11 June 2006 (UTC)
• File:Phases_Venus.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/11/Phases_Venus.jpg License: Attribution Contributors: Transferred from fr.wikipedia; transfer was stated to be made by User:Mu301. Original artist: Statis Kalyvas - VT-2004 programme
(Original uploader was Sting at fr.wikipedia)
• File:Phobos_colour_2008.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/5c/Phobos_colour_2008.jpg License: Public
domain Contributors: NASA/JPL-Caltech/University of Arizona Original artist: NASA/JPL-Caltech/University of Arizona
• File:Pioneer_Venus_2_inspection.jpg Source: http://upload.wikimedia.org/wikipedia/commons/4/4c/Pioneer_Venus_2_inspection.
jpg License: Public domain Contributors: http://nix.larc.nasa.gov/info;jsessionid=6v6flfypvl37?id=AC77-0376-8&orgid=9 Original artist:
NASA Ames Research Center (NASA-ARC)
• File:Pioneer_Venus_orbiter.jpg Source: http://upload.wikimedia.org/wikipedia/commons/9/98/Pioneer_Venus_orbiter.jpg License:
Public domain Contributors: ? Original artist: ?
• File:Portal-puzzle.svg Source: http://upload.wikimedia.org/wikipedia/en/f/fd/Portal-puzzle.svg License: Public domain Contributors: ?
Original artist: ?
• File:Portrait_of_Jupiter_from_Cassini.jpg Source:
http://upload.wikimedia.org/wikipedia/commons/7/75/Portrait_of_Jupiter_
from_Cassini.jpg License:
Public domain Contributors:
http://photojournal.jpl.nasa.gov/catalog/PIA04866 Original artist:
NASA/JPL/Space Science Institute
• File:Pot_of_gold_upclose.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/81/Pot_of_gold_upclose.jpg License: Public
domain Contributors: Transferred from en.wikipedia; transferred to Commons by User:Mike Peel using CommonsHelper. Primary source:
http://mars.nasa.gov/mer/gallery/press/spirit/20040615a.html Original artist: NASA. Original uploader was Stanthejeep at en.wikipedia
• File:Proteus_(Voyager_2).jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/83/Proteus_%28Voyager_2%29.jpg License: Public domain Contributors: 1989N1 Surface Detail (PIA00062) Original artist: Voyager 2, NASA
• File:Retrogadation1.png Source: http://upload.wikimedia.org/wikipedia/commons/e/e7/Retrogadation1.png License: Public domain
Contributors: self by W!B: (using StarOffice Draw) Original artist: W!B:
• File:Rotatingsaturnhexagon.gif Source:
Public domain Contributors:
http://upload.wikimedia.org/wikipedia/commons/b/bd/Rotatingsaturnhexagon.gif License:
• http://photojournal.jpl.nasa.gov/catalog/PIA09187 Original artist: NASA
• File:Saturn'{}s_A_Ring_From_the_Inside_Out.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/0d/Saturn%27s_A_
Ring_From_the_Inside_Out.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA05075 Original artist:
NASA/JPL/University of Colorado
7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES
133
• File:Saturn'{}s_double_aurorae_(captured_by_the_Hubble_Space_Telescope).jpg Source: http://upload.wikimedia.org/wikipedia/
commons/b/b1/Saturn%27s_double_aurorae_%28captured_by_the_Hubble_Space_Telescope%29.jpg License: Public domain Contributors: http://hubblesite.org/newscenter/archive/releases/2010/09/image/a/ (direct link)
Original artist: NASA, ESA, and Jonathan Nichols (University of Leicester)
• File:Saturn,_Earth_size_comparison.jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/39/Saturn%2C_Earth_size_
comparison.jpg License: Public domain Contributors: ? Original artist: The original uploader was Brian0918 at English Wikipedia
• File:Saturn-27-03-04.jpeg Source: http://upload.wikimedia.org/wikipedia/commons/c/c0/Saturn-27-03-04.jpeg License: Attribution
Contributors: Homepage of Rochus Hess Original artist: Rochus Hess
• File:Saturn-bonatti.PNG Source: http://upload.wikimedia.org/wikipedia/commons/8/8a/Saturn-bonatti.PNG License: Public domain
Contributors: Guido Bonatti, De Astronomia Libri X (Basel, Nicolaus Pruknerus, 1550) Original artist: Nicolaus Pruknerus, Guido Bonatti
• File:Saturn.ogg Source: http://upload.wikimedia.org/wikipedia/commons/c/c6/Saturn.ogg License: CC BY-SA 3.0 Contributors:
• Derivative of Saturn Original artist: Speaker: Mangst
Authors of the article
• File:Saturn_Equinox_09212014.jpg Source: http://upload.wikimedia.org/wikipedia/commons/d/d6/Saturn_Equinox_09212014.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA11667 Original artist: NASA/JPL/Space Science Institute
• File:Saturn_Robert_Hooke_1666.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/27/Saturn_Robert_Hooke_1666.jpg
License: Public domain Contributors: Philosophical Transactions (Royal Society publication) Original artist: Robert Hooke
• File:Saturn_Storm.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/29/Saturn_Storm.jpg License: Public domain Contributors: http://www.jpl.nasa.gov/news/news.cfm?release=2011-203 Original artist: NASA/JPL-Caltech/SSI
• File:Saturn_diagram.svg Source: http://upload.wikimedia.org/wikipedia/commons/2/2d/Saturn_diagram.svg License: CC BY-SA 3.0
Contributors: Own work Original artist: Kelvinsong
• File:Saturn_eclipse.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/ba/Saturn_eclipse.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA08329 (compressed version of http://photojournal.jpl.nasa.gov/tiff/PIA08329.tif)
Original artist: NASA/JPL/Space Science Institute
• File:Saturn_from_Cassini_Orbiter_(2007-01-19).jpg Source: http://upload.wikimedia.org/wikipedia/commons/4/47/Saturn_from_
Cassini_Orbiter_%282007-01-19%29.jpg License: Public domain Contributors: ? Original artist: ?
• File:Saturn_in_natural_colors_(captured_by_the_Hubble_Space_Telescope).jpg Source: http://upload.wikimedia.org/wikipedia/
commons/d/d4/Saturn_in_natural_colors_%28captured_by_the_Hubble_Space_Telescope%29.jpg License: Public domain Contributors:
http://www.spacetelescope.org/images/html/opo9828c.html (direct link)
Original artist: Hubble Heritage Team (AURA/STScI/NASA/ESA)
• File:Saturn_symbol.svg Source: http://upload.wikimedia.org/wikipedia/commons/7/74/Saturn_symbol.svg License: Public domain Contributors: Own work Original artist: Lexicon
• File:Saturnoppositions.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/c6/Saturnoppositions.jpg License: CC-BY-SA3.0 Contributors: ? Original artist: ?
• File:Sol454_Marte_spirit.jpg Source: http://upload.wikimedia.org/wikipedia/commons/4/41/Sol454_Marte_spirit.jpg License: Public
domain Contributors: http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20050420a.html Original artist: NASA/JPL
• File:SolarSystem_OrdersOfMagnitude_Sun-Jupiter-Earth-Moon.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/
02/SolarSystem_OrdersOfMagnitude_Sun-Jupiter-Earth-Moon.jpg License: CC BY-SA 3.0 Contributors:
• File:The Sun by the Atmospheric Imaging Assembly of NASA's Solar Dynamics Observatory - 20100819.jpg Original artist: Tdadamemd
• File:Solar_system.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/83/Solar_system.jpg License: Public domain Contributors: ? Original artist: ?
• File:Solarsystem3DJupiter.gif Source: http://upload.wikimedia.org/wikipedia/commons/0/08/Solarsystem3DJupiter.gif License: CC
BY-SA 3.0 Contributors: Own work Original artist: Lookang many thanks to author of original simulation = Todd K. Timberlake author of
Easy Java Simulation = Francisco Esquembre
• File:Sound-icon.svg Source: http://upload.wikimedia.org/wikipedia/commons/4/47/Sound-icon.svg License:
Derivative work from Silsor's versio Original artist: Crystal SVG icon set
LGPL Contributors:
• File:South_Polar_Cap_of_Mars_during_Martian_South_summer_2000.jpg Source:
http://upload.wikimedia.org/wikipedia/
Public domain Contributors:
commons/c/cb/South_Polar_Cap_of_Mars_during_Martian_South_summer_2000.jpg License:
http://photojournal.jpl.nasa.gov/catalog/PIA02393 http://www.msss.com/mars_images/moc/4_27_00_spcap/ file Original artist:
NASA/JPL/MSSS
• File:Speakerlink-new.svg Source: http://upload.wikimedia.org/wikipedia/commons/3/3b/Speakerlink-new.svg License: CC0 Contributors: Own work Original artist: Kelvinsong
• File:Spirit_Mars_Silica_April_20_2007.jpg Source:
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April_20_2007.jpg License: Public domain Contributors: ? Original artist: ?
• File:Symbol_book_class2.svg Source: http://upload.wikimedia.org/wikipedia/commons/8/89/Symbol_book_class2.svg License: CC
BY-SA 2.5 Contributors: Mad by Lokal_Profil by combining: Original artist: Lokal_Profil
• File:Synthetic_Venus_atmosphere_absorption_spectrum.gif Source:
http://upload.wikimedia.org/wikipedia/commons/3/34/
Synthetic_Venus_atmosphere_absorption_spectrum.gif License: CC BY-SA 3.0 Contributors: Own work using: Hitran on the Web
Information System http://hitran.iao.ru/ (Harvard-Smithsonian Center for Astrophysics (CFA), Cambridge, MA, USA and V.E. Zuev
Insitute of Atmosperic Optics (IAO), Tomsk, Russia). Original artist: Darekk2 using Hitran on the Web Information System
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CHAPTER 7. VENUS
• File:Synthetic_atmosphere_absorption_spectrum.gif Source:
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atmosphere_absorption_spectrum.gif License: CC BY-SA 3.0 Contributors: Own work using: Hitran on the Web Information System.
http://hitran.iao.ru/ (Harvard-Smithsonian Center for Astrophysics (CFA), Cambridge, MA, USA, V.E. Zuev Insitute of Atmosperic
Optics (IAO), Tomsk, Russia). Original artist: Darekk2 using Hitran on the Web Information System
• File:TerraformedVenus.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/b9/TerraformedVenus.jpg License: CC-BYSA-3.0 Contributors: Transferred from en.wikipedia to Commons. Original artist: Ittiz at English Wikipedia
• File:Terrestrial_Planets_Size_Comp_True_Color.png Source: http://upload.wikimedia.org/wikipedia/commons/a/a7/Terrestrial_
Planets_Size_Comp_True_Color.png License: Public domain Contributors: Own work, based on the [#Sources these sources]. Original
artist: Scooter20
• File:Tharsis_-_Valles_Marineris_MOLA_shaded_colorized_zoom_32.jpg Source:
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commons/2/22/Tharsis_-_Valles_Marineris_MOLA_shaded_colorized_zoom_32.jpg License: Public domain Contributors: JMARS
Original artist: NASA / JPL-Caltech / Arizona State University
• File:TheKuiperBelt_classes-en.svg Source: http://upload.wikimedia.org/wikipedia/commons/e/ed/TheKuiperBelt_classes-en.svg License: CC-BY-SA-3.0 Contributors: Image:TheKuiperBelt classes.PNG from wikimedia commons, uploaded by Eurocommuter; license :
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• File:The_Galilean_satellites_(the_four_largest_moons_of_Jupiter).tif Source: http://upload.wikimedia.org/wikipedia/commons/a/
af/The_Galilean_satellites_%28the_four_largest_moons_of_Jupiter%29.tif License: Public domain Contributors: http://photojournal.jpl.
nasa.gov/catalog/PIA01299 (direct link) Original artist: NASA/JPL/DLR
• File:Top_of_Atmosphere.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/be/Top_of_Atmosphere.jpg License: Public
domain Contributors: http://eol.jsc.nasa.gov/scripts/sseop/photo.pl?mission=ISS013&roll=E&frame=54329 Original artist: NASA Earth
Observatory
• File:Triton_moon_mosaic_Voyager_2_(large).jpg Source:
http://upload.wikimedia.org/wikipedia/commons/a/a6/Triton_moon_
mosaic_Voyager_2_%28large%29.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA00317 Original
artist: NASA / Jet Propulsion Lab / U.S. Geological Survey
• File:USGS-MarsMap-sim3292-20140714-crop.png
USGS-MarsMap-sim3292-20140714-crop.png License:
map.pdf Original artist: USGS
Source:
http://upload.wikimedia.org/wikipedia/commons/1/1f/
Public domain Contributors: http://pubs.usgs.gov/sim/3292/pdf/sim3292_
• File:Uranian_Magnetic_field.gif Source: http://upload.wikimedia.org/wikipedia/commons/a/a8/Uranian_Magnetic_field.gif License:
Public domain Contributors: ? Original artist: ?
• File:Uranian_moon_montage.jpg Source: http://upload.wikimedia.org/wikipedia/commons/6/6f/Uranian_moon_montage.jpg License:
Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA01361
http://ciclops.org/view/3461/Uranus_-_Montage_of_Uranus_five_largest_satellites Original artist: NASA/JPL
• File:Uranus'{}s_astrological_symbol.svg Source: http://upload.wikimedia.org/wikipedia/commons/9/94/Uranus%27s_astrological_
symbol.svg License: Public domain Contributors: Own work Original artist: Lexicon
• File:Uranus,_Earth_size_comparison.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/2a/Uranus%2C_Earth_size_
comparison.jpg License: Public domain Contributors: This image was made from NASA Earth America 2010.jpg and Uranus2.jpg (colour
adjustment) or Uranus (Edited).jpg Original artist: (old version user: Brian0918)
• File:Uranus-intern-en.png Source: http://upload.wikimedia.org/wikipedia/commons/f/fe/Uranus-intern-en.png License: Public domain
Contributors:
• Uranus-intern-de.png Original artist: Uranus-intern-de.png: FrancescoA
• File:Uranus2.jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/3d/Uranus2.jpg License: Public domain Contributors:
http://web.archive.org/web/20090119235457/http://planetquest.jpl.nasa.gov/milestones_show/slide1.html Original artist:
NASA/JPL/Voyager mission
• File:Uranus_Dark_spot.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/52/Uranus_Dark_spot.jpg License: Public domain Contributors: Transferred from en.wikipedia; transferred to Commons by User:Shizhao using CommonsHelper. Original artist: Original uploader was Ruslik0 at en.wikipedia
• File:Uranus_Final_Image.jpg Source: http://upload.wikimedia.org/wikipedia/commons/a/af/Uranus_Final_Image.jpg License: Public
domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA00143 Original artist: NASA
• File:Uranus_Orbit.gif Source: http://upload.wikimedia.org/wikipedia/commons/7/76/Uranus_Orbit.gif License: CC BY-SA 3.0 Contributors: Own work Original artist: Lookang many thanks to author of original simulation = Todd K. Timberlake author of Easy Java
Simulation = Francisco Esquembre
• File:Uranus_clouds.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/0e/Uranus_clouds.jpg License: Public domain Contributors: http://hubblesite.org/newscenter/archive/releases/2007/32/image/c/ Original artist: NASA, ESA, and M. Showalter (SETI Institute)
• File:Uranus_symbol.svg Source: http://upload.wikimedia.org/wikipedia/commons/f/f1/Uranus_symbol.svg License: Public domain
Contributors: Own work Original artist: Lexicon
• File:Uranusandrings.jpg Source: http://upload.wikimedia.org/wikipedia/commons/e/e4/Uranusandrings.jpg License: Public domain
Contributors: http://www.astronomy.com/asy/default.aspx?c=a&id=1226 : from http://hubblesite.org/newscenter/archive/releases/2002/
28/image/k/ or http://hubblesite.org/newscenter/archive/releases/1998/35/image/a/ Original artist: Hubble Space Telescope - NASA Marshall Space Flight Center
• File:Uranuscolour.png Source: http://upload.wikimedia.org/wikipedia/commons/f/fa/Uranuscolour.png License: Public domain Contributors: ? Original artist: ?
• File:Urbain_Le_Verrier.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/89/Urbain_Le_Verrier.jpg License: Public domain Contributors: Originally from en.wikipedia; description page is (was) here Original artist: User Magnus Manske on en.wikipedia
7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES
135
• File:Venera9.png Source: http://upload.wikimedia.org/wikipedia/en/1/15/Venera9.png License: ? Contributors:
http://www.mentallandscape.com/C_CatalogVenus.htm Original artist:
Soviet Union/Roscosmos/Venera 9
• File:Venus,_Earth_size_comparison.jpg Source:
http://upload.wikimedia.org/wikipedia/commons/9/92/Venus%2C_Earth_size_
comparison.jpg License: Public domain Contributors: The Earth seen from Apollo 17.jpg
Venus globe.jpg Original artist: NASA
Venus image: NASA / JPL (from Magellan)
• File:Venus-pacific-levelled.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/52/Venus-pacific-levelled.jpg License: CC
BY-SA 3.0 Contributors: http://en.wikipedia.org/wiki/Image:Venus_with_reflection.jpg Original artist: Brocken Inaglory
• File:Venus-real.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/51/Venus-real.jpg License: ? Contributors: http://
astrosurf.com/nunes/explor/explor_m10.htm Original artist: NASA/Ricardo Nunes
• File:Venus-real_color.jpg Source: http://upload.wikimedia.org/wikipedia/commons/e/e5/Venus-real_color.jpg License: ? Contributors:
http://www.astrosurf.com/nunes/explor/explor_m10.htm Original artist: NASA or Ricardo Nunes
• File:Venus2_mag_big.png Source: http://upload.wikimedia.org/wikipedia/commons/4/48/Venus2_mag_big.png License: Public domain
Contributors: Image from NASA website, and converted to PNG format Original artist: Magellan Team, JPL, NASA.
• File:VenusLanderTopo.jpg Source: http://upload.wikimedia.org/wikipedia/commons/9/98/VenusLanderTopo.jpg License: CC BY-SA
3.0 Contributors:
• Pioneer Original artist: Zamonin
• File:Venus_Drawing.jpg Source: http://upload.wikimedia.org/wikipedia/commons/7/73/Venus_Drawing.jpg License: Public domain
Contributors: Philosophical Transactions of the Royal Society Original artist: Captain James Cook and Charles Green
• File:Venus_Rover.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/15/Venus_Rover.jpg License: Public domain Contributors: ? Original artist: ?
• File:Venus_airplane.JPG Source: http://upload.wikimedia.org/wikipedia/en/f/f7/Venus_airplane.JPG License: PD Contributors: ? Original artist: ?
• File:Venus_globe.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/85/Venus_globe.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA00104 Original artist: NASA
• File:Venus_structure.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/cc/Venus_structure.jpg License: CC-BY-SA-3.0
Contributors: ? Original artist: ?
• File:Venus_symbol.svg Source: http://upload.wikimedia.org/wikipedia/commons/6/66/Venus_symbol.svg License: Public domain Contributors: Own work Unicode U+2640 (♀). Original artist: Kyle the hacker
• File:Venusorbitsolarsystem.gif Source: http://upload.wikimedia.org/wikipedia/commons/b/b7/Venusorbitsolarsystem.gif License: CC
BY-SA 3.0 Contributors: Own work Original artist: Lookang many thanks to author of original simulation = Todd K. Timberlake author of
Easy Java Simulation = Francisco Esquembre
• File:Venuspioneeruv.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/bc/Venuspioneeruv.jpg License: Public domain
Contributors: NSSDC Photo Gallery Venus direct link to the big TIFF Version:ftp://nssdcftp.gsfc.nasa.gov/photo_gallery/hi-res/planetary/
venus/pvo_uv_790226.tiff Original artist: NASA
• File:Venustransit_2004-06-08_07-49.jpg Source: http://upload.wikimedia.org/wikipedia/commons/d/db/Venustransit_2004-06-08_
07-49.jpg License: CC-BY-SA-3.0 Contributors: photo taken by Jan Herold (German Wikipedian) Original artist: de:Benutzer:Klingon
• File:Vénus_télescope.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/cc/V%C3%A9nus_t%C3%A9lescope.jpg License: GFDL Contributors: http://astrosurf.com/lecleire/2007/venuscolor_100907_05h22.jpg Original artist: Marc Lecleire
• File:War-of-the-worlds-tripod.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/5a/War-of-the-worlds-tripod.jpg License: Public domain Contributors: ? Original artist: Henrique Alvim Correa
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Contributors: Own work Original artist: User:Bastique, User:Ramac et al.
• File:Wikinews-logo.svg Source: http://upload.wikimedia.org/wikipedia/commons/2/24/Wikinews-logo.svg License: CC BY-SA 3.0
Contributors: This is a cropped version of Image:Wikinews-logo-en.png. Original artist: Vectorized by Simon 01:05, 2 August 2006 (UTC)
Updated by Time3000 17 April 2007 to use official Wikinews colours and appear correctly on dark backgrounds. Originally uploaded by
Simon.
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Contributors: ? Original artist: ?
• File:Wikisource-logo.svg Source: http://upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg License: CC BY-SA 3.0
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• File:Wiktionary-logo-en.svg Source: http://upload.wikimedia.org/wikipedia/commons/f/f8/Wiktionary-logo-en.svg License: Public domain Contributors: Vector version of Image:Wiktionary-logo-en.png. Original artist: Vectorized by Fvasconcellos (talk · contribs), based
on original logo tossed together by Brion Vibber
• File:William_Herschel01.jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/36/William_Herschel01.jpg License: Public
domain Contributors:
National Portrait Gallery: NPG 98
Original artist: Lemuel Francis Abbott
7.12.3
Content license
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