Large moons of the solar system: Titan

1. Large moons of the solar system: Titan • This next slide compares the terrestrial planets with the Earth’s Moon, the four Galilean moons of Jupiter, and Titan, the largest moon of Saturn. • Titan is the only moon in the solar system which has an atmosphere. • The atmosphere is mostly nitrogen and thicker than even Earth’s atmosphere.

3. Titan, as seen by the Cassini spacecraftfalse color on the left, infrared on the right

4. Rivers are seen on the surface of Titan as the probe “Huygens” descended to the surface. It landed and took pictures (right).

5. Radar sweeps of the North pole of Titan, taken by the Cassini spacecraft, showing lakes of methane and ethane. Flat areas in radar images are probably liquid surfaces, and are colored blue to resemble features on Earth. The radar image has no color in reality. (late 2007)

6. A lake (or sea) near the North pole of Titan, taken by Cassini, compared to Lake Superior on Earth.

7. Titan’s Atmosphere.

8. Triton Triton, the large moon of Neptune, may be a captured Kuiper-belt Object (KBO).

9. Medium-sized moons of the solar system • There are 12 medium-sized moons of the solar system, mostly around Saturn and Uranus. • These have a variety of features, and some are truly strange because they are some kind of aggregate object.

10. The Cassini spacecraft has returned detailed pictures of many of these smaller moons of Saturn. • We will just look at some in alphabetical order. • Notice that most of these are icy objects but are large enough to be round and have lots of craters. • In addition, some of them show cracking like the moon Europa of Jupiter. • Enceladus seems to be producing ice and water vapor and this contributes to the “E” ring of Saturn.

11. Medium-sized Saturnian Moons, compared to the Earth’s Moon

12. Dione

13. Enceladus

14. Enceladus A series of holes can be seen in the cracks

15. Enceladus appears to be releasing jets of water vapor and ice crystals, in this false-color image, which may be adding to Saturn’s E ring.

16. Iapetus - the trailing side has regions which are losing water to the white areas.

17. Rhea another view of a bright crater – probably relatively recent.

18. Tethys

19. Phoebe, an example of a smaller moon. (which might be a captured KBO !)

20. Moons of Uranus and Neptune (except Triton)

21. Ariel, a moon of Uranus

22. Miranda (a moon of Uranus) appears fragmented and jumbled together from various pieces.

23. Ch. 7Dwarf Planets and Small Solar System Bodies There are several kinds of objects in our Solar System Terrestrial planets and Jovian planets, with satellites (moons) Dwarf planets (which can also have moons) and “small solar system bodies” – asteroids, comets and meteoroids Objects are still being classified: Kuiper Belt Objects, Plutoids, Plutinos, Trans-Neptunian Objects (TNOs), Oort cloud objects

24. The period of Pluto’s orbit is 248 years.

25. Pluto and Charon are almost like a double planet. Pluto has at least two smaller moons: Nix and Hydra.

26. The Pluto–Charon Orbit is so unusual that it probably means Charon is captured, and not co-evolved with Pluto

27. Eris is a dwarf planet even further than Pluto.

28. Asteroids: three major groupsThe Asteroid beltTrojan AsteroidsNear-Earth Objects (NEOs)

29. This is a plot of actual positions of known comets and asteroids (April 1, 2005). This shows the inner solar system, out to Jupiter. Notice most of these are in the asteroid belt between Mars and Jupiter.

30. Expanding the first plot, we get a plot of known comets and asteroids in the region around the Earth. Fortunately, there aren’t very many of these Near Earth Objects (NEOs).

31. This is the view from the side, i.e., in the ecliptic plane, of the plot of the objects in the inner solar system.

33. Ceres, the largest asteroid, is also a dwarf planet.

34. Asteroids and meteoroidsare small “rocky” objectsThe main difference between the two is size.

35. Some asteroids have been studied up close. Asteroid Eros

36. Asteroid Eros was imaged by a spacecraft which then landed on it and sent back data on its composition.

37. Close-up pictures of Eros crater and surface. Crater about 3 mi across Photo of area 12 m across

38. The DAWN spacecraft was in orbit around Vesta, the second-largest of the asteroids in the Asteroid Belt, for almost a year, and is now on its way to Ceres. http://www.nasa.gov/mission_pages/dawn/main/index.html http://dawn.jpl.nasa.gov/ http://en.wikipedia.org/wiki/4_Vesta http://dawn.jpl.nasa.gov/mission/dawn_fact_sheet.pdf

39. Lagrange points are places where asteroids will be trapped in the orbit of Jupiter.

40. This is another plot of actual positions of known comets and asteroids (April 1, 2005). This shows the outer solar system, with the orbit of Jupiter and its Trojan asteroids. Notice there is another belt of objects out past Neptune.

41. This shows the outer solar system, past the orbit of Jupiter. This is the view from the side, i.e., in the ecliptic plane. Notice that the comets are coming from all directions, but the other objects are in the ecliptic plane.

42. Dwarf Planets and Small Solar-System Bodies • In 2006 three objects—Pluto, Ceres, and Eris—were classified as dwarf planets. Later, we added Haumea and Makemake. • Pluto, a KBO and dwarf planet, is an icy world that may well resemble Triton. • Other objects orbit the Sun beyond Neptune. For example, at least 1277 KBO’s have been observed. A few potential Oort cloud objects have also been identified. • http://solarsystem.nasa.gov/planets/index.cfm

43. Halley’s Comet was last seen in 1986. The orbital period is 76 years, so it will be back in 2062.

44. Comet Tails: ion tail and dust tail Comet Hale-Bopp (1997) had two distinctive tails: http://antwrp.gsfc.nasa.gov/apod/ap050522.html

45. A Comet Trajectory is usually a very narrow ellipse, with eccentricity near 1.0Some comets appear to come from almost 100,000 A.U. from the Sun, in a region called the Oort cloud.

46. Comet Reservoirs: the Oort Cloud the Kuiper Belt (pronounced Kye-per)

47. Halley’s Comet close-up by a passing spacecraft

48. Short-period comets result when a comet is deviated from a highly-eccentric orbit by the influence of a Jovian planet. Fragmentation of a comet can occur as it passes Earth.

50. Meteor Trails in the night sky