Reading updated: Chapter 9 Assigned seating on Thursday for a group activity

1. “Friendship is like peeing yourself; everyone can see it, but only you get the warm feeling it brings.” Funnyquotes.com http://sdbv.missouristate.edu/mreed/CLASS/A113Fa19 HW1 is on the course web page now and due Thursday in class. Reading updated: Chapter 9 Assigned seating on Thursday for a group activity

2. Homework • This will be done both on paper and using clickers. • HW will be assigned (often out of the book), and you will do it on paper. On the due date, I will have converted the questions to multiple choice, which you will answer using your clickers. You will also turn in your paper copy.

3. Quizzes Quiz questions cover current lecture material. You may use your notes and consult (quietly) with your neighbors. You are allowed to take 2 quizzes on paper. (I keep track.)

4. Atmospheres

5. What determines an atmosphere?

6. If the particles of atmosphere move fast enough, they escape into space. This is determined by: 1) mass of planet (more massive planets have more gravity) 2) mass of gas particles (larger particles travel slower) 3) temperature (determines how fast particles move)

7. For a hot object (planet/moon) to have an atmosphere, the atmosphere must be a heavy gas or the planet must be massive (high gravity). For a small object to have an atmosphere, the atmosphere must be a heavy gas, or the planet must be cold. For an object to have an atmosphere made of light gases, the planet must be massive, or very cold. It is easier to make large molecules when temperatures are cold.

8. The amazing planet EPIC 228813918b orbits its star every 4.3 hours. It is an Earth-massed planet and likely 52% iron with a silicate mantle. If this planet has an atmosphere, it must be: A) very cold to keep an atmosphere. B) extremely massive gas particles. C) extremely light gas particles. D) very hot to keep an atmosphere.

9. The amazing planet EPIC 228813918b orbits its star every 4.3 hours. It is an Earth-massed planet and likely 52% iron with a silicate mantle. If this planet has an atmosphere, it must be: A) very cold to keep an atmosphere. B) extremely massive gas particles. C) extremely light gas particles. D) very hot to keep an atmosphere.

10. The Earth-Moon system is dynamic.It seems like it is constant, but it is always changing. Similarly, our solar system seems like the same ol' thing. But in fact it is in the process of changing all the time!!!!

11. Water on the Moon? There are areas on the Moon that never receive direct sunlight. IF ice can get in there, it will not evaporate.

12. Eureka! Experiments on several satellites detected the signature of water on both the North and South Poles of the Moon. Each pole possibly contains at least a small-ish lake's worth of water-ice.

14. Where did all that water come from? Possibly from comets in the early solar system

15. Quiz 2: Which of the following statements is true? A) The Earth and Moon are the same as they have always been. Nothing changes with time on their surfaces or between them. B) The Earth and Moon are always changing, especially the Earth’s surface and orbit/spin between the Earth and Moon. C) The Earth and Moon orbit/spin is changing, but the surfaces of both objects has never changed. D) Only the Earth’s surface is changing with time, nothing else.

16. Review of what we’ve learned from the Earth-Moon system.

17. Surface age based on cratering 1) Smothered with craters; the surface is 4+ billion years old. (e.g. Lunar Highlands) 2) medium (-heavy?) cratered; 3.5 billion years old. (e.g. Lunar maria) 3) lightly cratered; ~200-500 million years old. (e.g. Earth's surface) 4) no craters; <few million years old.

18. How old is this surface? A) <few Myrs B) ~300 Myrs C) 2 Gyrs D) 4 Gyrs

19. How old is this surface? D) 4 Gyrs

20. How old is this surface? A) <few Myrs B) ~300 Myrs C) 2 Gyrs D) 4 Gyrs

21. How old is this surface? C) 2 Gyrs

22. Surface age based on cratering If a surface is NOT 4+ Gyrs, there must be a reason for that. Some form of erosion/resurfacing.

23. Color Variation 1) Composition (different colors made of different stuff) 2) Temperature (solid, liquid, or gas can change color) 3) Altitude (shading) Well-defined features usually mean solid. Hazy features usually mean gas. Smooth (featureless) usually means liquid.

24. A) Solid B) Liquid C) Gas

25. C) Gas

26. Quiz 2: A) Solid B) Liquid C) Gas

27. A) Solid

28. We assume that all objects in our solar system were made at the same time. So any younger surfaces indicate geologic processes. Solar system Age: 4.6 billion years.

29. Tides: Objects want to be tidally locked. It is the lowest energy state.Smaller things will tidally lock to larger things. Water: is very common in space. Surface processes include: plate tectonics, volcanoes, wind/water erosion

30. How does a planet get a moon? • It forms along with the planet: • Captured: • Split from planet: • Formed from a ring of material that was made by a giant collision. What are the consequences of each of these? Composition and Orbit

31. If the particles of atmosphere move fast enough, they escape into space. This is determined by: 1) mass of planet (more massive planets have more gravity) 2) mass of gas particles (larger particles travel slower) 3) temperature (determines how fast particles move)

32. Now that we have our baseline. It's time to exploreour solar system!!

33. Aside:Kepler's 3 laws of planetary motion 1) Planets travel in elliptical orbits (not circles) with the Sun at one focus. 2) Planets travel faster when they are closer to the Sun, such that a line, connecting the Sun and the planet, sweeps out equal area in equal time. 3) The square of the planet's orbital period is proportional to the cube of the semimajor axis (roughly its orbital distance).

34. Rule 1: Elliptical Orbits.

35. Equal area over equal time- means planets travel faster when closer to the Sun and slower when farther away.

36. Another example

38. Square of orbital period = cube of average orbital distance. P2=a3

39. Astronomical Unit (AU): The average distance between the Earth and the Sun. 1.5x1011m = 1.5 x 108km. (1 km= 0.6 miles) UNITS: In this class we mostly use the MKS system: meters, kilograms, and seconds

40. Starting with the Terrestrial planets.

41. MercuryWhat do you see and what does it mean?

43. Mercury • Old, heavily cratered surface. Probably of similar age as the highlands on the Moon: about 4 billions years old. • Some smooth areas which may be evidence of later volcanism (lava flows, like the mare on the Moon). • Globally cracked surface indicates that Mercury's surface solidified first (as expected) and as the mantle solidified, Mercury shrank slightly (by only 1 km in radius!), cracking the crust.

44. Mercury • Density: 5.4 gm/cc • Structure • Thin cracked rocky crust • Rocky mantle Iron core- 75% the size of the planet. Some of the core is probably molten (liquid). Temperature: Daytime 441F, Night -279F Atmosphere (yes, it has one!): Thin atmosphere created by solar wind blasting the surface (made of sodium mostly). It evaporates into space. 1 trillionth of Earth's pressure No moons.

45. Mercury, Unusual Spin/Orbit 3:2 Spin/Orbit resonance. • One sidereal day is 59 Earth days. • One solar day is 176 Earth days. • One orbital period is 88 Earth days. This is a form of tidal locking!

46. Messenger results: Ice in craters (0.1-1 trillion tons of water ice). • Larger Fe core and partially liquid • Magnetic field is uneven (South pole is weaker) • Atmosphere changes with distance. • Surface is sulfur-rich. 10X Earth’s