Ring World 1. Mass EarthSaturn 195.2 (x 10 24 kg) 5.97568 2.
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Transcript of Ring World 1. Mass EarthSaturn 195.2 (x 10 24 kg) 5.97568 2.
Size
Earth Saturn
Radius 1 9.45
Equatorial 6378 60,268
Polar 6357 54,364
Oblateness 0.3% 9.8%
Look for the flattening in the next photo.
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Density
Earth Saturn
100% 12.5
kg/m3 5515 687
Saturn has the lowest density of all the planets and moons.
Saturn would float in water!
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Large Magnetosphere
• Saturn’s magnetosphere is about 1/5th as large as Jupiter’s.– This is expected because Saturn has a
thinner conducting mantle of metallic H than Jupiter has.
• It’s 20x weaker than Jupiter’s field.– It’s actually only 68% as strong as Earth’s!
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Magnetosphere
• Jupiter’s magnetosphere is tipped slightly to its rotation, and is complex in structure
• Saturn’s magnetosphere is aligned almost perfectly with its rotation (axisymmetric), and its structure is very simple.
• Interesting feature: a ring current.
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Equatorial Ring Current
• Saturn’s moons Enceladus, Dione, and Tethys are enclosed in a torus of ions (like Jupiter’s Io).
• This torus is outside the major rings (but inside the thin, tenuous E ring).
• A current of about 10 million amps flows through this outer ring.
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Chemical Composition
• 96.3% H 3.25% He (by volume)
• Traces of methane (CH4), ammonia (NH3), water, ammonium hydrosulfide (NH4SH)
• Like Jupiter, there is a mantle of metallic H under a gaseous H envelope.
• Rocky / metallic core
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Saturn’s Orbit
• Average distance from the sun:
1.43 billion km (9.6 A.U.)
• Perihelion: 1.35 billion km
• Aphelion: 1.51 billion km
• Orbit Eccentricity: 0.056 (slightly more eccentric than Jupiter’s orbit)
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Orbit (2)
• Orbital Period: 29.5 years– Orbital Velocity: 9.7 km/s
• Inclination of orbit to ecliptic: 2.5o
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Saturn’s Rotation
• Rotational Period: 10.66 hours (10h 40m)
• Saturn has zonal winds, like Jupiter, but the colors are more muted.
• The rotational axis is tilted 26.7o to the ecliptic. This makes for a periodic tilt in the rings as viewed from the earth.
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The Rings !
• 2 (3) rings visible to the naked eye.
– separated by visible gaps.
• 3 more rings visible telescopically
• A new ring appears to be forming!
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Movie
Dustyring“spokes”
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Rings are Dynamic, not Static
• Dusty spokes indicate that the rings may be able to change on a short time frame.
• There are also periodic “ripples” in part of the rings…evidence of a collision between the rings & a comet or asteroid.
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Here’s a site with more info about the spiralaround the F ring.
http://www.aim.ufr-physique.univ-paris7.fr/CHARNOZ/homepage/SPIRAL/spiral_uk.htm
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Shepherd Moons
• Collisions between ring particles should remove kinetic energy from some particles, transfer kinetic energy to others.
– Slower particles should fall into Saturn.– Faster particles should leave the ring.
– Net: the rings should spread out and dissipate.
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The Larger Moons
• They’re all ice balls, but they’re not all the same.
• Mimas Enceladus Tethys• Dione Rhea Titan• Iapetus
• All of these moons are in synchronous rotation (leading vs. trailing hemisphere differences)
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Geysers of water & water vapor erupt fromEnceladus’ south pole region.
Hot spots have been discovered here by Cassini.44
Titan 5150 km diameter 1880 kg/m3
Ganymede 5262 km dia. 1940 kg/m3
How can Titan have a thick atmosphere, when Ganymede doesn’t?
Atmosphere of N2
heavily laden withhydrocarbons:methane ethane
Very smoggy
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Iapetussooty leading hemispherebright trailing hemisphere
equatorial ridge
What’s thesource ofthe soot?
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Missions to Saturn
• Pioneer 11– Launched 1973, flyby 1979.– Transmitted low-resolution photos of Saturn,
rings, moons.
• Voyager 1– Launched 1977, flyby 1980– Transmitted 900+ photos of the moons.– Discovered complexity of rings & nature of
Titan’s atmosphere.62
Missions to Saturn (2)
• Voyager 2– Launched 1977, flyby 1981– 1150 photographs of the moons
• Cassini Orbiter with Huygens probe to Titan’s surface.– Launched 1997, arrived in orbit July 1, 2004.
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Cassini’s Mission• Cassini is designed to photograph and
map Saturn & its moons in visible, infrared, and ultraviolet wavelengths.
• It has a magnetometer, magnetic imager, and plasma imager to closely study Saturn’s magnetic field.
• Huygens probe landed on Titan on January 14, 2005.
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