Announcements Friday Nov 10

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AnnouncementsFriday Nov 10

• Star party Wednesday results
• 50 pts Adam, Jordan, Justin, Josh
• 25 pts EC Dana, Jed, Amanda, Brandon, Jamie,
• See me if your name isnt on list
• Homework 12
• Last homework! (I will drop 2 lowest homework
  scores, top 10 count)
• Posted on web
• Exam 3 November 29 (Wed after Thanksgiving
  break)
• Todays lecture
• Terrestrial global climate change - update
• CO2 history update
• Milankovich effect, solar forcing, snowball
  Earth
• Saturn
• Titan, Cassini
• Uranus
• NASA film on discovery of Uranus

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• Long-term terrestrial climate change an update
  (separate PPT file)

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Saturns Satellites

• One planet sized satellite, Titan
• Intermediate in size between Mercury and Mars.
• Six moderate-sized satellites
• Very low densities (probably mostly ice).
• All synchronously orbit in the Saturns
  equatorial plane.
• Twenty-eight tiny satellites
• Might be captured asteroids.
• Might be jagged remnants of collisions.

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Titan has a thick, opaque atmosphere rich in
methane, nitrogen and hydrocarbons.
The surface of Titan, the second largest moon in
the solar system, is obscured by thick clouds.
Originally in the form of NH3, the Suns
radiation likely liberated the hydrogen which
escaped. Methane probably condenses into
droplets and falls as rain.
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Saturns largest satellite Titan2nd largest
satellite in solar system radius 5150 km vs.
Jupiters Ganymede 5260 km, but larger than
Mercury, 4878 km)
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Surface features on Titan

• Cassini IR image (right)
• Bright region Xanadu
• Dark areas (volcanic?)
• streaky features from winds?

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Dark areas Tarry hydrocarbon deposits (lakes?)
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Image from Huygens probe during descent

• Image taken from 8 km altitude
• Shoreline with hills and drainage channels?
• Note much too cold for liquid water!!
• Previously conjecture Methane oceans probably
  not.

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Titan Sand Dunes
Sand dunes on Earth
Sand dunes on Titan
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Image of Titans surface

• Pebbles are mostly water ice
• Dark areas though to be rain from hydrocarbon
  haze (e.g. methane) in atmosphere
• Surface temperature is 94 K (-290 F) not
  exactly a tropical paradise!
• Rock sizes are 5-20 cm (a few inchs)

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The icy surfaces of Saturns six moderate-sized
moons provide clues to their histories.
The smallest of the six has an enormous impact
crater among many other craters.
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The icy surfaces of Saturns six moderate-sized
moons provide clues to their histories.
Few craters and many ice flows on its young
surface suggests internal tidal heating from
Dione and Saturn
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The icy surfaces of Saturns six moderate-sized
moons provide clues to their histories.
Mostly heavily cratered with a curious, smooth
plains region of solidified water and ammonia
lava.
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The icy surfaces of Saturns six moderate-sized
moons provide clues to their histories.
Dione has a heavily cratered leading side and a
smooth trailing side.
e
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The icy surfaces of Saturns six moderate-sized
moons provide clues to their histories.
Also has a heavily cratered leading side and a
smoother trailing side.
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The icy surfaces of Saturns six moderate-sized
moons provide clues to their histories.
Also has a heavily cratered leading side which is
abnormally dark and a smoother and brighter
trailing side.
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The icy surfaces of Saturns six moderate-sized
moons provide clues to their histories.
The six seem to come in pairs of sizes.
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A Saturn-orbiting spacecraft, CASSINI, and a
Titan lander, HUYGENS, are providing a wealth of
new information.

• The enormous Cassini spacecraft arrived at Saturn
  in 2004. It will spend four years orbiting Saturn
  and studying the planet, rings, and moons.
• The Huygens Probe and parachuted into Titans
  atmosphere in January 2005, sending back detailed
  information before it landed.
• The orbits have been significantly reconfigured
  to account for any Doppler shifts in Huygens
  radio transmissions.

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Cassini Spacecraft
RPWS (University of Iowa)
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University of Iowa RPWS Instrument

• The objective of the RPWS investigation is to
  study radio and plasma waves in the vicinity of
  Saturn and during the flight to Saturn. This
  objective includes studies of
• Radio emissions
• Plasma waves
• Lightning
• Dust impacts
• Plasma densities and temperatures
• Plasma density fluctuations
• Regions investigated include
• Saturn's magnetosphere
• Titan's ionosphere
• Solar wind
• Jupiter's magnetosphere
• Earth, Venus, and Asteroids

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Where is Cassini right now? Image from Cassini
Nov 9 2006
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Cassini Orbit at Saturn
Saturn
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Huygens Probe Descent into Titans
atmosphere(November 27, 2004)
The Huygens probe survived, it transmitted data
for about 30 min.
Probe weighs 350 kg (770 lbs), diameter 2.7m (8ft)
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Cassini Orbits after Huygens probe(4 year
mission planned)
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Saturn Review Questions

• Who discovered that Saturn has rings?
• Galileo (1610), although he didnt see rings
  clearly. Huygens (1655) was the first astronomer
  to clearly see and report the rings
• Are Saturns rings actually solid bands that
  encircle the planet?
• No, they are small particles independently
  orbiting Saturn
• What is the composition and size of the ring
  particles?
• Ring particles are ice and ice-covered rocks,
  size from microns to 10m
• How do Saturns satellites affect the shape of
  its rings?
• There are several gaps in the rings which are
  tidally resonant with satellites, e.g. Cassini
  division and satellite Mimas (12 period, 11.3 h
  vs 22.6 h)
• Why are the color variations in Saturns
  atmosphere less dramatic than those on Jupiter?
• Saturn is less massive (1/3 Jupiter), so surface
  gravity is less, and three layers of the
  atmosphere (NH3, NH4SH, H2O) are more extended
  (300km vs. 75km) so we mostly see the top layer
  only.
• Why is Saturn more oblate than Jupiter?
• Saturn has similar rotation period but less
  gravity, so its more oblate (10 vs. 6)
• How does Saturns atmospheric helium compare with
  Jupiter?
• Saturns atmosphere has much less helium (3 vs.
  13 by number),
• Why does Saturn, emit even more radiation than it
  receives from the Sun than Jupiter?
• Helium rain droplets may have fallen deep into
  interior, releasing heat from gravitational energy

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Saturn Review questions cont

• How is it possible for Saturns moon Titan to
  have an atmosphere? (It is the only solar system
  satellite with an atmosphere)
• Titan is both massive enough and cool enough to
  retain heavy hydrocarbons in its atmosphere.
• What is Titans atmospheric composition?
• Mostly hydrocarbons e.g. methane, ethane,
  acetylene.
• What kinds of geologic activity are seen on
  Saturns other satellites?
• Enceladus has a geologically young surface
  (very icy, high albedo, few craters), probably
  caused by tidal heating from Saturn and the
  satellite Dione
• What plans are there for future exploration of
  the Saturnian system?
• Cassini (launched 1997) will arrive at Saturn in
  July 2004, launch Huygens probe into Titans
  atmosphere (Nov 2004)