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Jovian Planets
Jupiter in the IR and visible
Cassini 2000
Cassini
Chevrons
Discussion
Why do you think weather patterns on Jupiter
can last for centuries, while those on Earth
rarely last for more than a few days?
Comet Shoemaker-Levy 9 1993
Discussion
What do you think caused all these
comets to line up in this neat little row?
Galileo pictures
Discussion
The clouds on Saturn are made of the same
material as those on Jupiter, methane,
ammonium and water.
Why are Saturn’s clouds much blander looking
than Jupiter’s if the composition of the clouds
is so similar?
Saturn’s atmosphere
Hydrogen
Helium
Water
Methane
Ammonia
97%
3%
0.1%
0.2%
0.03%
Saturn produces more internal Heat
than Jupiter
Even though Saturn is less massive and nearly as
big as Jupiter, it produces 25% more heat per kg
than Jupiter.
Also Saturn’s atmosphere has only 3.3% He to
Jupiter’s 13.6% although we think the overall
composition of the two planets is about the
same.
Discussion
Why do you think Saturn produces more
heat per kg than Jupiter and why don’t we
see the He in its atmosphere? Where
could it have gone?
Discussion
Saturn’s winds have been clocked at 1100 mi/hr,
much faster than Jupiter’s. How can you explain
this given that Saturn is twice as far from the
Sun as Jupiter.
Discussion
While weather patterns like Jupiter’s great red
spot do appear on Saturn they tend to be short
lived. Why do you think this is?
Saturn’s tilt
Galilean Moons
Discussion
From Earth the Galilean satellites appear only as
points of light, yet before the space age
astronomers were able to determine each of the
satellites rotation rates and found that they are
all in synchronous rotation. How could this be
accomplished?
Albedo
Io
Europa
Ganymede
Callisto
Moon
Mercury
Mars
0.63
0.64
0.43
0.17
0.11
0.12
0.15
Discussion
What would you expect the result would be
of exposing methane CH4 ice to ultraviolet
light? Why do things in the outer solar
system, composed largely of ices, often
appear very dark?
Discussion
How did astronomers determine the size of
the Galilean satellites before the Pioneer and
Voyager flybys and HST?
Sizes and mass
Io
Europa
Ganymede
Callisto
Moon
Mercury
Mars
km
3642
3120
5268
4800
3476
4880
6794
MMoon
1.22
0.63
2.02
1.47
1.00
4.49
8.73
Densities of the Galilean
Satellites
1.
2.
3.
4.
Io
Europa
Ganymede
Callisto
3.53 g/cm3
3.02 g/cm3
1.94 g/cm3
1.85 g/cm3
Discussion
Why do you think the Galilean Satellites get less
dense as the distance from Jupiter increases?
The orbits
The orbits of the inner three Galilean satellites
are coupled in a 1:2:4 resonance.
The orbital period of Europa is twice that of Io
while that of Ganymede is 4 times that of Io.
Discussion
What do you think the effect of this
resonance is on the orbit Io?
Discussion
Do you think Io had more or less impacts over
its history than the Earth’s Moon? Why?
Io & the Moon
Discussion
Io has no impact craters. What does this tell
you about the surface of Io?
Discussion
Io is about the same size as the Earth’s Moon.
Why is Earth’s Moon geologically dead while
Io is so active? Why didn’t Io cool at the
same rate as the Moon did?
Tidal Heating
Discussion
Normally, tidal friction will cause the orbit of
the satellite to become more circular with time.
Why didn’t this happen with Jupiter’s moon Io?