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Jupiter and Saturn
Chapter 24
Jupiter
• Jupiter is the most massive of the Jovian
(outer) planets
• It contains nearly ¾ of all the
planetary matter in our solar
system
• Jupiter has 64 objects that are
orbiting around it at different
times
http://www.gearthblog.com/blog/archives/2006/04/google_jupiter.html
– 49/50 are officially moons, while the other 14/15
are unofficially (provisional) considered moons
Surveying Jupiter
• Jupiter’s diameter is 11 times Earth’s and its
mass is 318 times that of Earth’s
• It is composed mostly of hydrogen and helium
with traces of methane, ammonia, and water
• Jupiter is slightly flattened – it is 6.37% larger
in diameter, through its equator, than it is
through its poles
• Jupiter emits twice as much energy as it
receives from the sun
Jupiter’s Atmosphere
• Jupiter’s atmosphere is not deep
– Information from the Galileo space probe and
computer models come up with an atmosphere
about 1,000 km in thickness
• That number seems high, but when we look at Jupiter’s
diameter of 72,000 km it makes up only about 1% of its
radius – in comparison Earth’s atmosphere is about
2.5% of its radius
Jupiter’s Atmosphere
• The clouds of Jupiter and organized into dark
belts and bright zones
– Zones appear to be high-pressure regions of rising
gas that cool as it rises and forms clouds higher in
the atmosphere where they receive more sunlight
and look brighter
– Belts are low-pressure regions with sinking gas
and lower clouds that are not as brightly lit
• These two work together to create the circulation in
the atmosphere
Jupiter’s Atmosphere
• Great Red Spot is a
large circulation
(similar to a hurricane
on Earth) in the
atmosphere of Jupiter
that has been
observed for over 330
years
– It is twice the size of
Earth
http://hubblesite.org/gallery/album/pr1999029a/
Jupiter’s Ring
• Jupiter’s ring was discovered in 1979 by the
Voyager 1 spacecraft
– Very faint (dark) in comparison to Saturn’s rings
because they are composed of mostly rock (silicate
particles) instead of rock and ice like Saturn’s
• Roche limit is the minimum distance between a
planet and a satellite that holds itself together
by its own gravity
– If a satellite’s orbit brings it within its planet’s Roche
limit, tidal forces will pull the satellite apart
Comet Impact on Jupiter
• Shoemaker-Levy 9 was a
comet that struck
Jupiter in 1994
• Hit Jupiter and released
energy equivalent to a
few million megatons of
TNT
– Bomb dropped on
Hiroshima in WW2 was
only about 0.15 megaton
http://www.aem.umn.edu/people/faculty/shield/comet/comet.html
The History of Jupiter
• Jupiter formed from the colder gases of the outer
solar nebula, where ices were able to condense
• It became massive enough to trap hydrogen and
helium gas directly from the solar nebula
• The hydrogen takes the form of liquid metallic
hydrogen, which is a very good electrical conductor
• The planet’s rapid rotation, coupled with the
outward flow of heat from its interior, drives a
dynamo effect that produces a powerful magnetic
field
Jupiter’s Family of Moons
• Callisto: The Ancient Face
– Outermost of Jupiter’s four large
moons
– Photographs from Voyager and
Galileo spacecraft show that it has
a dark and icy surface that is heavily cratered
– It is believed through computer models that
Callisto has a layer of liquid water roughly 10 km
in thickness somewhere below its icy crust
http://science.nasa.gov/science-news/science-at-nasa/1998/ast22oct98_2/
Jupiter’s Family of Moons
• Ganymede: A Hidden Past
– It is larger than the moon
and Mercury and over ¾
the diameter of Mars
– It is the largest satellite in our
solar system
– Its surface shows presence
of activity
http://solarsystem.nasa.gov/multimedia/display.cfm?Category=Planets&IM_ID=11684
• About a 1/3 of the surface is
old, dark, and cratered the rest is marked by lighter parallel
grooves
– Current theories for groove formation suggest that tension in the
crust stretched the landscape repeatedly to form the grooves
Jupiter’s Family of Moons
• Europa: A Hidden Ocean
– Is smaller than Callisto and
Ganymede, but has traces of
water on its surface but that
water seems to lie in an icy
crust less than 100 km thick
http://www.wired.co.uk/news/archive/2011-03/08/nasa-decadal-review
• The long lines crossing the surface suggest a renewal
process
– They look like cracks in the ice crust where water from below
has welled up and frozen
– Europa is geologically active
Jupiter’s Family of Moons
• Io: Bursting Energy
– Inner most of the Galilean
moons
– Volcanism is continuous on Io
• It is heated by Jupiter and the
volcanism is caused because of the
strong tidal forces from Jupiter
http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level2/io.html
The History of the Galilean Moons
• The minor moons of Jupiter are probably
captured asteroids, but the Galilean moons
more than likely formed in a disk-shaped
nebula around Jupiter – a mini-solar nebula
– We know that Jupiter was very hot when it
formed, so, just like the terrestrial and Jovian
planets formed in the solar nebula, the inner
moons, Io and Europa, formed from rocky
material, and the outer moons incorporated more
ices
Planet Saturn
• Saturn is only about a 1/3 the mass of Jupiter
and about 16% smaller in radius
• Saturn’s density is less than water – which
means if we could put into a big enough
container it would float in water
http://en.wikipedia.org/wiki/File:Saturn_during_Equinox.jpg
Planet Saturn
• It radiates almost twice as much energy as it
receives from the sun
– It is hotter than astronomers thought it would be and
they believe helium in the liquid hydrogen interior is
condensing into droplets and falling inward and
release energy as they pick up speed which heats the
planet
• Saturn’s atmosphere is rich in hydrogen and
contains the belt-zone circulation just like Jupiter
– In comparison to Jupiter Saturn’s atmosphere is
unremarkable (no visual storms or cloud formations)
Saturn’s Rings
• Saturn’s rings are made up of roughly 1000
ringlets no wider than 2 km
• The rings are composed of a combination of
small rock particles and ice
• The rings more than likely were formed
because a moon or icy planetesimal came too
close to Saturn
– Roche limit wouldn’t allow these objects to stay
together and would have pulverized them into
what we now see as rings
• Believed to have happened in last 100,000 years
The History of Saturn
• The planet formed in the outer solar nebula,
where ice particles were stable
• It grew rapidly and became massive enough to
capture hydrogen and helium
• Just like Jupiter many mysteries remain about
this planet
Saturn’s Moons
• Most sources say that Saturn has 62 moons, most
of them are small and dead
– Just like Jupiter a most of these are captured asteroids
or planetesimals
http://saturn.jpl.nasa.gov/science/moons/
Titan
• Saturn’s largest satellite is a giant ice moon with a
thick atmosphere and a mysterious surface
• The amazing thing about its atmosphere is that it
has been able to hold on to it with its small size
• Been able to hold on to atmosphere because of its cold
temperature
– 95% nitrogen and 5% methane
– Titan's brew of organic compounds is probably like the
early Earth's chemistry. Its very cold temperatures may
then have preserved a record of what the early Earth
was like before life formed.
Some info for Titan was copied from Nick Strobel's Astronomy Notes. Go to his site at www.astronomynotes.com for the updated and corrected version