1. The most distant planet known to the ancients is NASA’s latest target for exploration.

2. Cassini image, October 6, 2002

3. Saturn Facts Average orbital distance9.54 A.U. Orbital period29.42 yr Diameter120,536 km(Earth =12,756) Rotation period0.44 days Mass568e24 kg Average Density0.687 g/cc(water = 1.0) Obliquity26.73 degrees SurfaceNone – we see cloud tops Composition89.7% H, 9.9% He, 0.8% H 2 O by volume With some methane and ammonia And traces of acetylene, ethylene, etc Satellites18 Inner, >33 total NASA ExplorationPioneer 11, launched 1973 Voyager 1, Voyager 2, launched 1977 Cassini/Huygens, launched 1997

4. Rhea Enceladus Dione Tethys Mimas Titan

5. Name Semimajor Axis (km) Period (days) Eccentricity Inclination (deg) Mean Radius (km)Mass (10^20 kg) Pan133,5830.5750~ 0 10 Atlas137,6400.6019~ 0 16 Prometheus139,3500.6129860.00240.0500.0014 Pandora141,7000.6288040.00420.0420.0013 Epimetheus151,4220.6945900.0090.34590.0055 Janus151,4720.6945900.0070.14890.0198 Mimas185,5200.94242180.02021.531990.385 Enceladus238,0201.3702180.00450.022490.73 Tethys294,6601.8878020.00001.095306.22 Telesto294,6601.887802~ 0 11 Calypso294,6601.887802~ 0 10 Dione377,4002.7369150.00220.0256010.52 Helene377,4002.7369150.0050.216 Rhea527,0404.5175000.00100.3576423.1 Titan1,221,85015.9454210.02920.3325751345.5 Hyperion1,481,10021.2766090.10420.43143 Iapetus3,561,30079.3301830.02837.5271815.9 Phoebe12,952,000550.480.163175.3110

7. Notes on satellite dynamics Moons are 1:1 spin-orbit coupled (and so have leading, trailing sides) Mimas:Tethys 2:1 resonance Enceladus:Dione 2:1 Titan:Hyperion 4:3 Dione has leading Trojan: Helene Tethys has Trojans Telesto and Calypso Janus and Epimethus 1:1 horseshoe resonance “Cassini division” is a Mimas resonance A-ring structures caused by Pandora, Prometheus, and Janus Pan causes Encke gap in A ring

8. Rings of Saturn FeatureBoundaries (km)Optical DepthNotes InnerOuter D Ring66,90074,65810^-5Contains narrow ringlets at 67,580 and 71,710 km. C Ring74,65891,9750.05 to 0.35Isolated "plateaus" among a surrounding, fainter ring. Titan Ringlet77,87177,896A narrow, eccentric ringlet inside a gap in the C Ring. Maxwell Ringlet87,49187,555A narrow, eccentric ringlet inside a gap in the C Ring. 1.470 Rs Ringlet88,71688,732A narrow, eccentric ringlet inside a gap in the C Ring. 1.495 Rs Ringlet90,17190,232A narrow, eccentric ringlet inside a gap in the C Ring. B Ring91,975117,5070.4 to 2.5 Contains fine structure on all scales. The most opaque of Saturn's rings. Cassini Division117,507122,3400 to 0.1 The prominent gap between the A and B Rings. It contains several features of low optical depth. Huygens Ringlet117,825118,185 A narrow, eccentric ringlet near the inner edge of the Cassini Division. A Ring122,340136,7800.4 to 1.0 A fairly uniform ring with many density and bending waves near its outer edge. Encke Gap133,410133,7400 A gap in the A Ring "shepherded" open by the embedded moon Pan. One or more faint ringlets are also present. Keeler Gap136,510136,5500An empty gap near the outer edge of the A Ring. F Ring (core)140,2190.1 to 1 An eccentric ringlet containing clumps and kinks. Based on its eccentricity, its radial limits are 140,194 to 140,244 km. G Ring166,000173,20010^-6A very faint, isolated dust ring. E Ring180,000480,00010^-6 A broad, faint dust ring encompassing the orbits of Mimas through Dione. Densest near the orbit of Enceladus. Up to ~ 30,000 km thick.

18. Inferred Ring Particle Size Distribution

19. F-ring, Pandora, Prometheus (Voyager 2)

20. Voyager 2: discovery image of satellite Pan

25. Cassini, Huygens probe, and Launch vehicle adapter

26. Cassini/Huygens key dates June 11, 2004 – Flyby of Phoebe July 1, 2004 – Crossing of ring plane during Saturn-orbit insertion sequence Dec 25, 2004 – Huygens probe separates Jan 14, 2005 – Huygens begins its descent into Titan’s atmosphere

27. Jean Dominique Cassini Saw “Cassini Division”, and satellites Iapetus, Rhea, Tethys, and Dione

28. Christiaan Huygens Discovered Titan Proposed flat ring system

34. Pandora, F-ring, Prometheus, Cassini orbiter

35. Enceladus: Ice geysers supply material for E ring?

36. Izanagi and Izanami craters on Rhea