Saturn

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Rotation period as fast as Jupiter, as well as
differential rotation rates at poles and equator
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Saturn

• Second largest planet with rings
• Atmosphere composition similar to Jupiter, but
  less metallic H2
• Density 0.69 g/cc (could float on water!)
• Twice as far from the Sun as Jupiter
• Surface Temp 95 K
• Deep clouds, strong winds (1700 Km/hr)
• Intrinsic magnetic field is 1000 x Earths (but
  because of its size it is only 70 of Earths
  just outside the atmosphere)

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Rings of SaturnHighly structured and stable
formations
Polar caps are illuminated due to electrical
activity at the two magnetic poles
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Orientation of rings and different views of Saturn
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Distances of Rings(How many?)
2.5 times radius of planet
The Ring systems lie within about 2.5 x Saturns
radius. i.e. within Roche limit
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Rings and Gaps Thousands of rings interspersed
with gaps
Voyager view Before that there were thought to
be only a few
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Main ring formations and divisions
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Rings and Moons

• What are the rings made up of ?
• What keeps the rings stable and in orbit ?
• Saturn has 62 moons, more than any other planet
  (Titan and Enceladus most interesting !)
• All Jovian planets are now known to have rings
• Saturns rings are most shiny made of icy
  rocks, in independent Keplerian orbits, above the
  equator

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Composition of Rings

• Dirty, icy, snowballs from about 1/1000 of an
  inch (dust particles) to 10 yards most about a
  foot
• Origin (i) breakup of satellite(s), (ii)
  incomplete formation (a la asteroid belt !)
• Orbits are stable and particles do not collide
• Rings are stable due to gravitational
  interaction with small Shepherding Moons that lie
  among the ring structures

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The Roche Limit

• Gravitational stability limit, out to about 2.5
  times the radius of the planet
• Any object without intrinsic gravity (such as a
  pile of gravel) will break up inside the Roche
  limit due to tidal effects a moon with
  sufficient mass and under its own gravity need
  not break up
• All rings, and small shepherding moons, lie
  within the Roche limit larger moons are outside

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Gaps in rings contain shepherding moons
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Moons and ringsShepherding moons within rings
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Shepherding moons and a ring
Ring particles in orbital resonance with the
moons are ejected due to periodic gravitational
interaction, i.e. only particles whose periods
are NOT multiples of moons orbital periods
survive in the rings
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Asteriod Ripped Apart By Star Into Ring-like
Structures

• http//www.ibtimes.com/november-astronomy-findings
  -unprecedented-image-asteroid-ripped-apart-dead-st
  ar-2179852

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TITAN

• Titan is one of several large moons beyond the
  Roche limit
• Titan is most interesting, about 1.5 times the
  size of Earths moon and a density of 1.9 g/cc
• Second largest moon in the solar system

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TITAN Moon with (heavy) Atmosphere
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Intensities of Lines in Absorption Spectra Atoms
absorb energy
Emission spectra are a set of bright lines atoms
emit energy
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Observing Planets and Moons
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Spectra of Titan (Moon of Saturn)Methane (CH4)
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Infrared (heat) map of Titan
Infrared reflectivity indicates composition of
atmosphere
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Atmosphere of Titan

• Mostly nitrogen (80), argon, methane (CH4)
• Pressure 1.6 x Earths atmosphere
• Surface Temperature -300 F (95 K)
• CH4 and C2H6 (ethane ethyl alcohol) oceans,
• (half-mile deep) clouds, rain, ice, snow
• Orangish color due to smog
• Oxygen locked in ice

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Titan and Origin of Life ?

• Many organic, hydrocarbon compounds HCN, C3H8,
  etc.
• Present conditions similar to primordial
  conditions on Earth in the first billion years
• Slow evolution because of cold
• NASA probe Cassini is now studying Titan
• Terraforming Titan!! ? Heat up to release
  Oxygen, which would covert methane to CO2 (like
  Mars) CH4 O2 ?? CO2 2H plant life to follow

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CASSINI
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Enceladus Water !
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Other moons heavily cratered
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Data on Some Saturn Moons