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Ring World

Ring World. 1. Mass. Earth Saturn 1 95.2 (x 10 24 kg) 5.97 568. 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. 3. 4. 5. Density. Earth Saturn

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Ring World

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  1. Ring World 1

  2. Mass EarthSaturn 1 95.2 (x 1024 kg) 5.97 568 2

  3. Size EarthSaturn 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. 3

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  6. 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! 6

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  8. 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! 8

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  10. 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. 10

  11. Evidence for Saturn’s Magnetic Field! 11

  12. 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. 12

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  14. 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 14

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  16. 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) 16

  17. Orbit (2) • Orbital Period: 29.5 years • Orbital Velocity: 9.7 km/s • Inclination of orbit to ecliptic: 2.5o 17

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  19. 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. 19

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  21. Notice the rotational storm. 21

  22. A red oval similar to Jupiter’s GRS. 22

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  24. apod.nasa.gov/apod/ap090111.html

  25. 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! 24

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  27. Pan orbits within the Encke Division 26

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  30. Movie Dusty ring “spokes” 29

  31. 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. 30

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  33. BraidedF ring The ring isn’t really braided, but has spirals around it. 32

  34. 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. 33

  35. The gravity of the shepherd moons focuses the rings. 34

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  37. Here’s a site with more info about the spiral around the F ring. http://www.aim.ufr-physique.univ-paris7.fr/CHARNOZ/homepage/SPIRAL/spiral_uk.htm 36

  38. Barely discernible new ring (with 2 new tiny moons) 37

  39. 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) 38

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  41. Mimas with HerschelCrater Mimas is about the size of Ohio 1150 kg/m3 40

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  44. Geysers of water & water vapor erupt fromEnceladus’ south pole region. Hot spots have been discovered here by Cassini. 43

  45. 44 Tethys has a gigantic canyon which nearly circles the moon. Ithaca Chasma

  46. Dione, leading hemisphereat left, trailing at right. 45

  47. Dione Direction of movement through space. 46

  48. Rhea 47

  49. Rhea also has those strange lighter stripes on its trailing hemisphere. 48

  50. Atmosphere of N2heavily laden with hydrocarbons: methane ethane Very smoggy Titan 5150 km diameter 1880 kg/m3Ganymede 5262 km dia. 1940 kg/m3How can Titan have a thick atmosphere, when Ganymede doesn’t? 49

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