Saturn

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Saturns Moon SystemMost extensive, complex moon
system in the solar system.Over 40 known moons.
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Most moons are covered with snow and ice. Some
are probably made almost entirely of H2O ice.
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Three natural groups exist

• over 11 small moons,
• 6 medium-sized moons,
• 1 large moon

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The one large moon is Titan. 5150 km in
diameterTitan is the second largest moon in the
solar system, only Ganymede is larger.
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Titan has a reddish color caused by an
atmosphere!!Voyager I passed very close to
Titan. (This cost Voyager I any more
exploration).
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A hazy smog layer obscures the surface.
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Titan was explored by a lander as part of the
Cassini mission.
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The lander found lakes and rivers of hydrocarbons
and also hydrocarbon rain.
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Titans atmosphere is thicker and denser than
Earths. The composition is N2- 90, Ar-10,
CH4-1 to 2.
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Sunlight causes chemical reactions in the
atmosphere, which might produce some of the
colors seen.
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Titans atmosphere contains ten times as much gas
as Earths. It extends ten times as far out into
space as Earths (due to lower gravity). The
lower surface temperature (94K) favors the
retention of the atmosphere.
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The six medium-sized moons are all spherical, and
are between 400 and 1500 km in diameter.
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The inner five are all composed of largely rock
and water ice. These five have circular,
synchronous orbits inside Titans orbit. We
discuss these in order from innermost to
outermost.
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Mimas - gravitational resonance affects the ring
particles causing gaps. Mimas has an enormous
crater on its leading face. This crater is named
Herschel and has a diameter 1/3 of the moons
diameter.
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Enceladus - Similar to Mimas. There is evidence
of large-scale volcanic activity. Many
lava-covered impact craters (the lava is water).
Volcanism on Enceladus replaces the particles
in the E-ring of Saturn.
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Tiger stripes
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Tethys - heavily-cratered reflective surfaces.
Tethys has a huge impact crater called Odysseus
(2/5 the diameter of the moon).
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Dione - The trailing face of Dione has prominent
bright streaks.
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Rhea - Saturns second largest moon. Heavily
cratered with an albedo of 0.6. The water ice on
its surface is very hard, so its craters look
like the Moons.
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Rhea has the wispy terrain. Light colored
streaks on the trailing side of the moon.
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Dione and Tethys
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Iapetus - orbits far beyond Titan on an inclined,
elliptic path. It has a huge black spot called
the Cassini Regio.
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Iapetus has a dark leading face with an albedo of
0.03 and a light trailing face with an albedo of
0.5.
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Smaller Moons
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Smaller moons Some of the moons are sweepers
that sweep out gaps in the rings.
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Atlas (top) and Pan (bottom)
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Prometheus and Pandora are the shepherd moons for
the F-ring.
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Prometheus
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Pandora
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Prometheus
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Pandora
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Prometheus
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Prometheus
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Beyond the F-ring lie the Co-orbital Satellites,
Janus and Epimethius. These two moons share an
orbit.
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The inner moon takes approximately 4 years to
lap the outer moon, and they exchange orbits
when they meet.
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Janus
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Janus
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Epimethius
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Epimethius
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The small moons, Telesto and Calypso have orbits
that are synchronized with the moon Tethys. One
orbits 60 ahead and the other orbits 60 behind
Tethys. These locations are called Lagrange
Points.
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The moon Helene is similarly synchronized with
Dione.
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The two outermost moons are Hyperion and Phoebe.
Phoebe is the only moon of Saturn with a
retrograde orbit. It is possible that it is a
captured moon.
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Hyperions rotation is not synchronous with its
orbit. This is because Hyperions orbit is not
circular due to the gravitational pull of Titan
in addition to Saturn.
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The combination of these two gravitational pulls
causes Hyperion to change its rotation speed and
its rotation axis. This is called chaotic
rotation.
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Mimas Enceladus Tethys Dione
Rhea Titan Hyperion Iapetus
Phoebe
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