1. © 2010 Pearson Education, Inc. Our Moon and other moons of the Solar System

2. © 2010 Pearson Education, Inc. Starter 1/25/13 What do you already know about our Moon?

3. © 2010 Pearson Education, Inc. What is a moon? A moon is a natural satellite of a planet or dwarf planet There are over 170 moons around the planets and dwarf planets in our solar system

4. © 2010 Pearson Education, Inc. Planets and numbers of moons PlanetNumber of known moons Mercury0 Venus0 Earth1 Mars2 Jupiter63 Saturn63 Uranus 27 Neptune13 Dwarf planet Pluto3 (maybe 4) Eris1

5. © 2010 Pearson Education, Inc. How do we explain the existence of our Moon?

6. © 2010 Pearson Education, Inc. Giant Impact Theory Between 4.4 and 5 billion years ago an object about the size of Mars struck a very young Earth and blasted material into orbit around Earth –The “youngest” Moon rocks are 4.4 billion years old The material from the collision came together by gravity (called accretion) and became our Moon. The Moon was much closer to the Earth when it first formed –It was between12,000-18,000 miles away –Now it is 240,000 miles away and moving away from us by 1.5 inches/year

7. © 2010 Pearson Education, Inc. Giant Impact

8. © 2010 Pearson Education, Inc. Why does the Moon look the way it does?

9. © 2010 Pearson Education, Inc. Impact Cratering Most cratering happened soon after the solar system formed – “the Late Heavy Bombardment” Craters are about 10 times wider than object that made them. Small craters greatly outnumber large ones.

10. © 2010 Pearson Education, Inc. Impact Craters Meteor Crater (Arizona) Tycho Crater (Moon)

11. © 2010 Pearson Education, Inc. Impact Craters on Mars “Standard” crater Impact into icy ground Eroded crater

12. © 2010 Pearson Education, Inc. Thought question Shouldn’t the Earth be covered in craters too? Why isn’t it?

13. © 2010 Pearson Education, Inc. Volcanism Volcanism happens when molten rock (magma) finds a path through the Earth’s crust (lithosphere) to the surface. Molten rock is called lava after it reaches the surface.

14. © 2010 Pearson Education, Inc. Lava and Volcanoes Runny lava makes flat lava plains. Slightly thicker lava makes broad shield volcanoes. Thickest lava makes steep stratovolcanoes.

15. © 2010 Pearson Education, Inc. The Lunar Maria were formed by volcanism Smooth, dark lunar maria are less heavily cratered than lunar highlands. Maria were made by floods of runny lava.

16. © 2010 Pearson Education, Inc. Formation of Lunar Maria Large impact crater weakens crust. Heat build- up allows lava to well up to surface. Early surface is covered with craters. Cooled lava is smoother and darker than surroundings.

17. © 2010 Pearson Education, Inc. The Moon is geologically dead Moon is considered geologically “dead” because geological processes have virtually stopped.

18. © 2010 Pearson Education, Inc. Do the Moon and Mercury have any atmosphere?

19. © 2010 Pearson Education, Inc. Exospheres of the Moon and Mercury Sensitive measurements show that the Moon and Mercury have virtually no atmosphere. The little gas there comes from impacts and the solar wind that eject surface atoms. Earth’s Moon Mercury

20. © 2010 Pearson Education, Inc. The Moon’s surface conditions No atmosphere No liquid water – frozen water at the poles Because of the lack of an atmosphere the moon experiences extreme temperatures –Daytime = 130  C (265°F) –Nighttime = -190  C (-310  F) The moon has 1/6 th of Earth’s gravity

21. © 2010 Pearson Education, Inc. Starter 2/7 Identify one similarity and one difference between our Moon and the other moons of the solar system?

22. © 2010 Pearson Education, Inc. What kinds of moons orbit the other planets of the solar system?

23. © 2010 Pearson Education, Inc. Sizes of Moons Small moons (< 300 km) “irregular” –No geological activity Medium-sized moons (300–1500 km) “regular” –Geological activity in the past (mostly) Large moons (> 1500 km) “regular” –Ongoing geological activity (mostly)

24. © 2010 Pearson Education, Inc. Small (or irregular) Moons These are far more numerous than the medium and large moons. They do not have enough gravity to be spherical: Most are “potato-shaped.”

25. © 2010 Pearson Education, Inc. They are captured asteroids or comets, so their orbits do not follow usual patterns – *retrograde and tilted orbits Small (or irregular) Moons

26. © 2010 Pearson Education, Inc. Captured Moons Mars has two moons (Phobos and Deimos) that are thought to be captured asteroids from the asteroid belt

27. © 2010 Pearson Education, Inc. Medium and Large (regular) Moons Enough self-gravity to be spherical Often have substantial amounts of ice Except for our Moon they formed in orbit around jovian planets (gas giants) *by accretion Circular orbits in same direction as planet rotation *around equator

28. © 2010 Pearson Education, Inc. Jupiter’s Galilean moons

29. © 2010 Pearson Education, Inc. Io Io is the most volcanically active body in the solar system

30. © 2010 Pearson Education, Inc. Io’s Volcanoes Volcanic eruptions continue to change Io’s surface.

31. © 2010 Pearson Education, Inc. Europa

32. © 2010 Pearson Education, Inc. Europa’s interior also warmed by tidal heating producing a possible ocean under the ice.

33. © 2010 Pearson Education, Inc. Ganymede Largest moon in the solar system Clear evidence of geological activity

34. © 2010 Pearson Education, Inc. Callisto “Classic” cratered iceball No evidence of geologic activity

35. © 2010 Pearson Education, Inc. Other interesting moons in the solar system

36. © 2010 Pearson Education, Inc. Titan Saturn’s largest moon Titan is the only moon in the solar system to have a thick atmosphere. It consists mostly of nitrogen with some argon, methane, and ethane.

37. © 2010 Pearson Education, Inc. Titan’s Surface Huygens probe provided first look at Titan’s surface in early 2005. It found liquid methane and “rocks” made of ice.

38. © 2010 Pearson Education, Inc. Enceladus Enceladus is a medium sized moon of Saturn Ice fountains of Enceladus suggest it may have a subsurface ocean.

39. © 2010 Pearson Education, Inc. Charon The largest moon of Pluto is also the largest moon relative to the size of its planet Charon is ½ the size of Pluto, and is thought to be ice-covered like Pluto as well

40. © 2010 Pearson Education, Inc. Top 12 largest moons in the solar system 1.Ganymede 2.Titan 3.Calisto 4.Io 5.The Moon 6.Europa 7. Titania 8. Rhea 9.Oberon 10.Iapetus 11.Charon 12.Umbriel

41. © 2010 Pearson Education, Inc. Top 10ish moons in the solar system (with other terrestrial bodies for comparison)