1. Plan for this week • The jovian planets • 5 major moons • Comets, asteroids, and Earth impacts

2. The jovian planets

3. The jovian planets • All very large • All rotate very fast • All made mostly of gaseous material

4. Jupiter

5. Jupiter

6. The Great Red Spot

7. Jupiter

8. Saturn

9. Saturn

11. Uranus

12. Neptune

13. Neptune

14. Data for the jovian planets

15. Jovian interiors • At the center, a dense core of rock, metal, and hydrogen compounds • Around the core is gaseous molecules • Jupiter and Saturn • Mostly hydrogen • Includes states of matter not found on Earth • Uranus and Neptune • Water, methane, hydrogen

18. The jovian moons • Some of the jovian moons are far more interesting than the planets themselves • There are more than 90 total • They come in all sizes

19. Small jovian moons

20. Medium sized jovian moons

21. Largejovianmoons

22. The jovian moons • The largest moons in the solar system are: • Ganymede (Jupiter) • Titan (Saturn) • Callisto (Jupiter) • Io (Jupiter) • ‘The Moon’ (Earth) • Europa (Jupiter) • Triton (Neptune)

23. The Galileanmoons

24. The Galilean moons • The four largest moons of Jupiter • Discovered by Galileo in the early 1600s • Very important historically • Proved that everything does not go around the Earth • Got Galileo in a lot of trouble!

25. The Galilean moons • Io • The closest one to Jupiter • Size: • Larger than Pluto • Smaller than Mercury • Experiences very strong tidal forces

26. Tidal forces Io (Other moons) Jupiter

27. The Galilean moons • Io is the most geologically active place in the solar system! • Volcanoes continuously erupting • Not a single impact crater on its surface

28. Io

29. The Galilean moons • Europa • The next moon out from Jupiter • Size: • Larger than Pluto • Smaller than the Moon or Mercury • Also experiences tidal forces • Surface is entirely covered with ice • May have a water ocean under the ice • A possible place for life?

30. Europa

31. Europa

32. The Galilean moons • Ganymede • The largest moon in the solar system • Larger than Pluto and Mercury! • (That’s all you need to know about it…)

33. Ganymede

34. The Galilean moons • Callisto • The fourth one (just for completeness)

35. Callisto

36. Saturn’s moons • Titan • Size: • The 2nd largest moon in the solar system • Larger than both Pluto and Mercury • The only moon in the solar system with a substantial atmosphere • Mostly nitrogen (like Earth!) • Atmospheric pressure = 1.5 x Earth’s • Wouldn’t need a space suit! (cold though…)

37. Titan

38. Pluto • The most distant planet - if it’s a planet! • Distance: 30 - 50 AU (40 average) • Orbit = 248 years • Rotation = 6.4 Earth-days • Has one moon: Charon • About half the size of Pluto

39. Pluto & Charon

40. Pluto & Charon

41. Planetary rings • All jovian planets have ring systems • All are made of small pieces of debris • Probably unformed moons, or moons that were broken apart by the planet’s gravity

42. Saturn’s rings • Small chunks of ice (mostly) • Incredibly thin • A single sheet of paper 3 football fields across! • Made of many ‘ringlets’

46. Asteroids • Chunks of rock and metal • Mostly in the asteroid belt - but not all of ‘em! • Earth crossing asteroids • Have orbits that bring them near Earth’s orbit

47. Comets • Chunks of ice, rock, & metal (‘dirty snowballs’) • Today in two locations: • The Kuiper belt • Beyond Neptune’s orbit • ~ 30 - 100 AU out • In the disk of the solar system • The Oort cloud • A sphere way, way beyond Neptune • ~ 50,000 AU out

48. A cometnucleus

50. Comets • If a comet ‘falls’ towards the Sun: • It begins to sublimate (solid --> gas) • Develops a tail • This tail always points away from the Sun