1. Neptune Uranus Size comparison of the Outer Planets Earth

2. Early telescopic observations of Saturn a. Galileo, 1610; b. Huygens 1655; c. Cassini 1676

4. Spacecraft that have visited Saturn Pioneer 11 flew within 21,000 km of Saturn on 1 September 1979, discovered two new moons and an additional ring, charted Saturn's magnetosphere and magnetic field and found its planet-size moon Titan, to be too cold for life. The Voyager 1 and 2 Saturn encounters occurred nine months apart, in November 1980 and August 1981. Discovers larger of internal to external heat: 2-to-1 compared to 1-to-1 for Jupiter. Cassini orbital insertion on July 1, 2004. Took first image of a moon (Phoebe) on June 11, 2004. Still working in April 2006: http://photojournal.jpl.nasa.gov/mission/Cassini Cassini dropped the Huygens probe into atmosphere of Titan on January 14, 2005.

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7. Cassini spacecraft; launched on Oct. 15, 1997 from KSC 7 Year cruise on Venus-Venus-Earth-Jupiter Gravity Assist Trajectory

8. The Cassini Spacecraft

10. Interior Structure of Saturn

11. Like on Jupiter, there are latitudinal bands of clouds and storms

12. Ribbon clouds in atmosphere – high-speed turbulence

13. Wind speeds at top of Saturn’s Atmosphere 1700 km/hr Opposite direction

15. Multiple Rings!CC AA BB Encke Gap F Cassini Division E Ring extends to 7.5 Saturn radii from cloud top DD

16. Structure: Non-symmetric on each side of Saturn

17. Braided F-Ring of Saturn due to co-orbiting “shepherd” moons

18. Two shepherd satellites confine Saturn’s narrow F ring. The outer shepherd gravitationally deflects ring particles inward, and the inner shepherd deflects ring particles outward.

19. Prometheus = 47 km, Density = 0.42

20. = 41 km, Density = 0.54 Pandora

21. Ring Spokes – Dust above the ring plane

23. The Smaller Moons of Saturn Atlas Prometheus Pandora Janus Epimetheus Telesto Calypso Helene

24. = 90 km, Density = 0.61 Janus

25. Epimetheus = 58 km, Density = 0.64

26. Mimas, 392 km in diameter Herschel Crater is 130 km wide and 10 km deep!

27. Enceladus – 500 km in diameter Diverse surface, with some tectonics

28. Enceladus

30. Tethys – 1,060 km in diameter. Heavily cratered, with some lineaments

31. Dione – 1,120 km in diameter. Bright surface swirls, many craters

32. Rhea – 1,530 km in diameter. Very heavily cratered

33. Pioneer 11 Voyager 1 Cassini visible light image Various spacecraft views of Titan – 5,150 km in diameter Cassini near- IR image

34. What do we know about Titan? It is the biggest of Saturn’s moons. Titan’s diameter of 5,150 km makes it larger than the planet Mercury with a diameter of 4,880 km and Pluto (2,350 km). Only Jupiter's moon Ganymede is larger. Three-and-a-quarter Earth Moons could fit inside Titan. Titan is the only moon known to have a large atmosphere – maybe thicker than Earth’s (>1,000 mb)! Its atmosphere is mostly nitrogen, just like the atmosphere surrounding Earth, but thicker. Its atmosphere contains methane and tiny amounts of oxygen.

35. Comparison of Titan’s atmosphere with Earth’s Important gases in Titan’s atmosphere

36. 1.Ethane-methane lakes 2. Moist convection in methane clouds 3. Sedimentation of aerosols 4. Elevated terrain washed by rain 1. 2. 3. 4.

37. January 14, 2005 – Huygens Probe sent to Titan’s surface

38. Huygens scientific instruments Aerosol Collector and Pyrolyzer: collects Titan's aerosols for chemical composition analysis; Descent Imager/Spectral Radiometer: makes spectral measurements and takes pictures of Titan's surface and atmospheric hazes; Doppler Wind Experiment: uses radio signals to deduce wind speeds on Titan; Gas Chromatograph/Mass Spectrometer: identifies and quantifies various atmospheric constituents on Titan; Surface Science Package: determines the physical properties of Titan's surface.

39. Radar Image of Titan’s surface – valley systems

40. Few impact craters seen on Titan – implies young surface

41. Horizon at 66 m 15 cm diameter 30 cm diameter Range 85 cm Range 240 cm Surface image from Huygens probe

42. Iapetus – 1,460 km in diameter. Striking albedo differences

43. Cassini Views of Iapetus Iapetus is 1,460 km diameter Orbits 59.1 Saturn radii from planet 100 km

44. What’s Interesting about Phoebe? Phoebe is roughly spherical and is ~220 km in diameter. Phoebe rotates on its axis every 9 hours and orbits Saturn in ~18 months. Its irregular, elliptical orbit is inclined ~30 degrees toward Saturn’s equator. Phoebe’s orbit is retrograde. Phoebe’s average distance from Saturn is 13 million km, which is ~4 times farther away from Saturn than its nearest neighbor, the moon Iapetus. Phoebe and Iapetus are the only major moons in the Saturn region that do not orbit close to the plane of Saturn’s equator. Unlike most major moons orbiting Saturn, Phoebe is very dark and reflects only 6 percent of the sunlight it receives.

45. Saturn’s moon Phoebe

46. Identification of surface materials on Phoebe

47. Saturn Summary