Saturn

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Saturn
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Bulk Properties

• Radius 9.5 Earth radii
• Mass 95 Earth masses
• Density 0.687 g/cm3
• Semi-major Axis 9.5 A.U. (9.0-10.0)
• Orbital Period 29.5 years
• Rotational Period 10.5 hours
• Differential rotation
• Oblate spheroid (even more than Jupiter)

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Saturns Atmosphere

• Composition
• 92 Hydrogen, 7 Helium
• Trace amounts of methane and ammonia
• Layers
• Ammonia clouds
• NH4HS clouds
• water clouds
• All three layers are thicker than on Jupiter

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Atmospheric Coloration

• Longitudinal Bands
• Not as prominent as on Jupiter
• Due to thickness of the outer layer of clouds
• Weather
• Zonal flow Eastward in the zones and Westward in
  the belts
• Very fast winds (1500km/hr)
• Helium precipitation
• A light shower of liquid helium constantly
  falling from the lower atmosphere toward the
  interior

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Saturns Interior

• Very similar to Jupiter
• Large rocky core
• Liquid metallic hydrogen
• Liquid molecular hydrogen
• Hydrogen/Helium atmosphere
• Magnetic field strength intermediate between
  Earth and Jupiter
• Large enough to contain the ring system and the
  innermost 16 moons (about the orbit of Titan)

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Saturns Rings

• First observed by Galileo in 1610
• Thought Saturn was a triple planet as it
  appeared to have bumps or ears
• Realized in 1659 (Christian Huygens) to be a flat
  ring system
• First ring feature (a dark band in the rings)
  found in 1675 by Giovanni Cassini

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Composition

• Small rocky and icy bodies
• Most about the size of a softball
• The ring system is only a few tens of meters
  thick
• Not one big ring, but several rings
• Original designations from outside in.
• A-ring (Contains the Encke gap)
• Cassini division
• B-ring
• C-ring
• Other rings discovered by Pioneer and Voyager
  probes
• Inside C-ring is the D-ring
• Outside A-ring is the F-ring and the E-ring
  (faint and very far)

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How did the rings form?

• Tidal forces increase nearer the planet
• If a body gets close enough that the tidal forces
  exceed the gravitational forces holding the
  object together, it breaks apart
• The distance at which this happens is called the
  Roche Limit
• It is believed that a moon was torn apart by
  tidal forces and formed the rings

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Ring Maintenance

• Orbital Resonance
• A particle orbiting in the Cassini Division has
  an orbital period exactly half that of Saturns
  innermost major moon (Mimas)
• The extra gravitational forces present at this
  distance stretches the original circular orbit
  into an elliptical one
• This eventually clears the area of particles,
  resulting in a low density gap

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Ring Maintenance

• Shepherd Satellites
• Small moons that orbit on either side of a
  ringlet
• The F-ring is surrounded by the orbits of
  Prometheus and Pandora
• Keeps the ring tightly confined in a narrow orbit
• Moonlets
• Small moons that sweep up ring debris and create
  small gaps
• Pan creates the Encke gap

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