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Earth and Other Planets
3 November 2015
Chapter 16
Great Idea:
Earth, one of the planets that orbit the Sun, formed
4.5 billion years ago from a great cloud of dust.
1
Chapter Outline
• The Formation of the Solar System
• Exploring the Solar System
• The Earth
2
The Formation of the
Solar System
3
Clues to the Origin
of the Solar System
• Solar system
– Objects gravitationally bound to Sun
• Deduction of origin
– Observations
• Earth
• Space
4
Clue #1: Planetary Orbits
• Features of solar system
– All planets orbit in same direction
– Orbits in same plane
– Most rotate in direction of orbit
5
Clue #2: Distribution of Mass
• Most material within Sun
• Two types of planets
– Terrestrial planets
– Jovian planets
• Other objects
– Moons, asteroids, comets
6
The Nebular Hypothesis
• Nebular
Hypothesis
– Cloud of dust and
gas
– 99% H and He
• Collapse of
nebula
– Planetary orbits
– Clumping of
matter
– Planetesimals
– Temperature
7
Basic Planet Categories
• Terrestrial planets
–
–
–
–
Mercury
Venus
Earth
Mars
• Jovian planets
–
–
–
–
Jupiter
Saturn
Uranus
Neptune
8
Some Conclusions
• Planets formed at same time as Sun
• Planetary and satellite/ring systems are
similar to remnants of dusty disks such
as that seen about stars being born
• Planet composition dependent upon
where it formed in solar system
9
Nebular Condensation
(protoplanet) Model
• Most remnant heat from collapse
retained near center
• After sun ignites, remaining dust
reaches an equilibrium temperature
• Different densities of the planets are
explained by condensation temperatures
• Nebular dust temperature increases to
center of nebula
10
Nebular Condensation Physics
• Energy absorbed per unit area from Sun =
energy emitted as thermal radiator
• Solar Flux = Lum (Sun) / 4 x distance2
• Flux emitted = constant x T4 [Stefan-Boltzmann]
• Concluding from above yields
T = constant / distance0.5
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Nebular Condensation Chemistry
Molecule
H2
H2O
CH4
NH3
FeSO4
SiO4
Freezing Point Distance from
Center
10 K
>100 AU
273 K
>10 AU
35 K
>35 AU
190 K
>8 AU
700 K
>1 AU
1000 K
>0.5 AU
12
Nebular Condensation Summary
• Solid Particles collide, stick together, sink
toward center
– Terrestrials -> rocky
– Jovians -> rocky core + ices + light gases
• Coolest, most massive collect H and He
• More collisions -> heating and differentiating
of interior
• Remnants flushed by solar wind
• Evolution of atmospheres
13
iClicker Question
The most abundant chemical element in
the solar nebula
A
Uranium
B
Iron
C
Hydrogen
D
Helium
E
Lithium
14
Pictorial View of Origins
15
Pictorial View Continued
16
HST Pictorial Evidence
17
HST Pictorial Evidence
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iClicker Question
As a planetary system and its star forms
the temperature in the core of the
nebula
A
Decreases in time
B
Increases in time
C
Remains the same over time
D
Cannot be determined
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iClicker Question
As a planetary system and its star forms
the rate of rotation of the nebula
A
Decreases in time
B
Increases in time
C
Remains the same over time
D
Cannot be determined
20
The Formation of Earth
• Planetesimals
– Combined (accretion)
to form earth
• Great bombardment
– Meteors
– Growth of planet
• 20 metric tons per day
21
Differentiation
• Differentiation
– Heat from collisions
– Dense material sank to
center
– Lighter material rose to
surface
• Structure
– Core
– Mantle
– Crust
22
Crust and Us
23
Earth’s Interior How We Know It
24
iClicker Question
Which of the
diagram
represents the
mantle of the
Earth?
A
B
C
D
E None of the
above.
25
iClicker Question
Which of the
diagram
represents the
outer core of the
Earth?
A
B
C
D
E None of the
above.
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iClicker Question
Energy transport from one region to
another by the movement of material as
in the mantle of the Earth is known as
A
chaos.
B
radiance.
C
conduction.
D
differentiation.
E
convection.
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iClicker Question
The existence of earthquake shadow zones
indicates that there is an abrupt change
between the properties of the mantle and
those of the core. Specifically, the
transverse wave shadow zone shows that the
outer core must be
A
solid.
B
liquid or semi-liquid.
C
gaseous.
D
similar to crustal material.
E
impossible to determine.
28
The Formation of the Moon
• Large object (asteroid close to size of
Mars) impacted earth
• Parts of mantle blown into orbit
• Moon formed from this material
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Planetary Idiosyncracies
• Cratering
– Mercury, Mars, Moon
– Few on Earth
• weathering
• Rotation
– Venus
– Earth’s axis
– Uranus
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The Evolution of
Planetary Atmospheres
• Earth’s atmosphere
– Early
– Outgassing
• Atmosphere was N2, CO2, H2, & H2O
– Gravitational escape
– Living organisms
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iClicker Question
•
All our observations of the Sun and
planets have been made from the
surface of the Earth.
–
–
A
B
True
False
32
iClicker Question
•
All planets and most of their moons
orbit in the same direction around the
Sun
–
–
A
B
True
False
33
iClicker Question
•
Almost all planets and moons rotate on
their axes in the same direction as the
planets orbit the Sun.
–
–
A
B
True
False
34
iClicker Question
•
What is the shape of our solar
system?
–
–
–
A
B
C
spherical (like a ball)
flat (like a dish)
tubular (like a hot dog)
35
iClicker Question
•
The mass in our solar system is evenly
distributed.
–
–
A
B
True
False
36
Exploring the Solar System
37
The Inner Solar System
• Mercury, Venus, Mars
– Mercury and Venus too hot for life
• Mars Exploration
– Multiple missions
– Found evidence of water
38
The Outer Solar System
• Jupiter, Saturn, Uranus,
Neptune
– Layered structure
– No solid surface
• Jupiter
– Comet Shoemaker-Levy 9
– Galileo spacecraft
• Saturn
– Cassini spacecraft
39
The Outer Solar System II
40
• Jupiter’s Moons
– Io, Europa, Ganymede, Callisto and 63 others known
• Saturn’s Moons
– Titan, Mimas, Hyperion and about 59 (61?) others
• Rings
Moons
and
Rings
– Ice and rock - more ice in Saturn’s rings
41
Dwarf
Planet
Pluto
Surprises
• It has moons
• Original moon discovered 1978
– Charon (KAIR’ en)
• Now more
– 2005 discovery of 2 additional
moons
– Named Nix and Hydra
– 2011 #4 is P4 (Kerberos)
– July 7, 2012 #5 is P5 (Styx)
42
Pluto’s Interior to Surface
Old -> New Model
• Model 1
– partially hydrated rock
core
– water ice layer II
– predominant water ice
layer I
• Model 2
– partially hydrated rock
core
– organics layer
– predominantly water ice
layer
43
The Launch of New Horizons Pluto Mission
17 Jan 2006
http://www.youtube.com/watch?v=KNJNaIoa5Hk
44
Io’s Volcanoes from New Horizons
45
46
Pluto
47
Pluto’s Methane (frozen)
48
Charon
49
Pluto
50
Pluto Atmosphere Detection
51
Pluto and Charon
52
Carbon Monoxide (Frozen)
53
Solar Wind at Pluto
54
Pluto “Heart” Region
55
Pluto
Mountain
Range
56
Nix and Hydra
57
Pluto, True Color
58
Asteroids, Comets,
and Meteors
• Asteroids
– Small rocky bodies
– Orbit sun
– Most in belt between Mars and Jupiter
• Comets
– Dirty snowballs
• Orbit outside Pluto
• Oort cloud
• Kuiper belt
– Halley’s Comet
– Stardust and Deep Impact missions
• Meteoroids, Meteors, and Meteorites
– Meteor showers
– Original solar system material
63
Planetary Summary
Mass
(Earth=1)
Density
(g/cm3)
Major
Constituents
Mercury
Venus
Earth
Mars
0.06
0.82
1.00
0.11
5.4
5.2
5.5
3.9
Rock, Iron
Rock, Iron
Rock, Iron
Rock, Iron
Jupiter
Saturn
318
95
1.3
0.7
H, He
H, He
Uranus
Neptune
14
17
1.3
1.7
Ices, H, He
Ices, H, He
Planet
64
iClicker Question
•
Mercury, Venus, Earth, and Mars are
called:
–
–
–
–
–
A
B
C
D
E
galaxial objects
standard planetoids
Jovian planets
terrestrial planets
dwarf planets
65
iClicker Question
•
Jupiter, Saturn, Uranus, and Neptune
are called:
–
–
–
–
–
A
B
C
D
E
galactic objects
standard planetoids
Jovian planets
terrestrial planets
dwarf planets
66
iClicker Question
•
The asteroid belt is located:
–
–
–
–
A
B
C
D
between the Sun and Mercury
between Mercury and Venus
between Mars and Jupiter
outside of our solar system
67
iClicker Question
•
Distinctive features of the solar system
such as the rotation of the Sun, orbits of
the planets, and the distribution of mass
into one large central object and lots of
much smaller orbiting bodies is explained by:
–
–
–
–
A
B
C
D
the Hubble theory
the nebular hypothesis
the Trefil and Hazen gambit
the relativity theory
68
iClicker Question
•
What are the Jovian planets primarily
composed of?
–
–
–
–
–
A
B
C
D
E
rocky substances
element 119 (Jo)
hydrogen and helium
iron (Fe)
silicon (Si)
69
iClicker Question
•
Outgassing and gravitational escape
are processes by which
–
–
–
–
A
B
C
D
planets form an atmosphere
space travel may become possible
solar systems form planets
string theory can be applied
70
iClicker Poll Question
•
Have you ever seen a meteor or
meteorite?
–
–
–
A
B
C
yes
no
don’t know what these are
71
iClicker Poll Question
•
Should future missions to the planets
carry people or robots?
–
–
–
–
A
People only
B
Robots only
C
People and robots
D
Neither, missions to planets are a
waste of money
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