SATURN

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SATURN
Pontus Cson Brandt The Johns Hopkins University
Applied Physics Laboratory
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OUTLINE

• The visible Saturn
• Satellites
• Rings
• Planet
• The invisible Saturn
• The magnetosphere
• Cassini
• ENA imaging
• Jupiter results
• Earth results

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Science Targets
Cassinis 5 groups of science objectives at
Saturn are
Saturn - the planet and its atmosphere
Magnetosphere
Saturns extensive Rings
Icy Satellites
Titan
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SATELLITES

• Saturn has 18 named satellites plus 13 recently
  discovered and as yet unnamed ones
• Of those moons for which rotation rates are
  known, all but Phoebe and Hyperion rotate
  synchronously.
• The three pairs Mimas-Tethys, Enceladus-Dione and
  Titan-Hyperion interact gravitationally in such a
  way as to maintain stable relationships between
  their orbits the period of Mimas' orbit is
  exactly half that of Tethys, they are thus said
  to be in a 12 resonance Enceladus-Dione are
  also 12 Titan-Hyperion are in a 34 resonance.
• In addition to the 18 named satellites, a dozen
  more have been reported and given provisional
  designations but not yet named.

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SATURN

• Composed primarily of hydrogen and helium the
  upper atmosphere of Saturn exhibits banding
  similar to that of Jupiter. Unlike Jupiter,
  however, the individual bands and clouds have
  little color variations.
• From Pioneer investigations, scientists
  discovered that the magnetic field of Saturn is
  aligned with the planet's axis of rotation,
  unlike the fields of Jupiter and Earth. This
  discovery has led to revisions in the theories on
  the origin of magnetic fields, which had
  previously relied on an offset between the
  field's axis and the planet's rotation axis to
  produce large planetary magnetic fields.
• Because of its fast rotation period of 10 h, the
  magnetic field can be pictured as stretched out
  by centrifugal forces. (more extreme at Jupiter).

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RINGS

• The slight color variation (false color. Part is
  in UV) reflects compositional differences.

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SPOKES

• Fine light and dark radial markings discovered in
  Voyager images revolve around the planet along
  with the rings. Informally termed "spokes", these
  structures are seen as dark markings in reflected
  light, yet turn to bright streaks when lit from
  the rear.  The spokes are probably formed by
  extremely small dust particles held in place by
  electrostatic forces.

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TITANWhy all the fuss?

• Near-infrared image of Titan's surface obtained
  from speckle images taken with the Keck
  telescope. The brightest regions reflect about
  15 of incoming light the dark region in the
  lower left reflects essentially no light,
  indicating that it is probably dark organic
  material, either liquid methane and ethane or a
  more complex solid.

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METHANE LAKES?

• Titan is the only moon in the solar system with a
  thick atmosphere surrounding it.
• The atmospheric pressure near Titan's surface is
  60 greater than Earth at sea level.
• The atmospheric temperature near Titan's surface
  is 95K (-178 C or -288 F).
• The thickness (extent) of Titan's atmosphere is
  about 10 times that of Earth.
• A thick haze at 200 km (120 mi) altitude hides
  Titan's surface at visible wavelengths.
• Titan's diameter is 5150 km (3200 mi), about 40
  as large as Earth.
• As on Earth, the most abundant gas in Titan's
  atmosphere is nitrogen.
• Methane is the second most abundant gas more
  than a dozen other gases are present.
• Sunlight could be converting the methane in
  Titan's atmosphere into large organic molecules.
  Titan's gravity would force any resulting
  molecules down to the surface. This raises the
  question of life forming in all this possible
  organic soup. 
• Titan is waterless, BUT adding water to this
  highly organic environment might just be what
  happened to Earth and created amino acids.
• Its a pre-historic real-time laboratory.
• The Huygens probe will be released during a Titan
  fly-by and land on the surface/lake sampling
  atmosphere and surface.

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Charge Exchange
A magnetically trapped ion captures an electron
from a neutral hydrogen atom...
creating an energetic neutral atom (ENA) that is
no longer trapped.
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MAGNETOSPHERE - INSTRUMENTATION
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SEEING THE MAGNETOSPHERE-EARTH
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SEEING THE MAGNETOSPHERE-JUPITER (Cassini
Flyby)
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SEEING THE MAGNETOSPHERE-SATURN
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SIMULATION OF SATURNS MAGNETOSPHERE DURING A
FLYBY
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MAGNETOSPHERIC DYNAMO

• A conducting fluid (plasma) moving in a magnetic
  field will induce an electric current.
• Faraday even postulated that it was the motion of
  Earths oceans that induced currents that were
  responsible for the Aurora.
• Jupiters aurora is probably caused by a dynamo
  effect.
• Any satellites (moons) will be electrically
  connected to Jupiter and feed currents that will
  produce a footprint on the surface of Jupiter.
• Earths aurora is caused by currents set up by
  plasma distributions and reconfiguration of the
  magnetic field.

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