“Time is an illusion. Lunchtime doubly so.” Ford Prefect, the Hitchhiker’s Guide to the Galaxy

1. “Time is an illusion. Lunchtime doubly so.” Ford Prefect, the Hitchhiker’s Guide to the Galaxy

2. Mercury • Density: 5.4 gm/cc • Structure • Rocky crust • Rocky mantle Iron core- outer part molten Temperature: Daytime 441F, Night -279F No moons.

3. Mercury, Unusual Spin/Orbit 3:2 Spin/Orbit resonance. This is a form of tidal locking!

4. Venus Describe Venus based on the next 3 images.

5. Through the clouds!This is a reflectivity map:smoother parts are lighter

6. Relief Map: Low areas are dark blue while high areas are red (the highest being white).

7. 1) Venus has some craters (surface Age estimate 500-800 million years old) 2) Lots of volcanic activity!! The entire surface was essentially re-written 500-800 million years ago! 3) Tectonic activity, but not as plates.

9. Density = 5.2 g/cc No moons

10. Bizarre Venus • Sidereal Rotation period: 243 days (longer than the year!) • Rotation is retrograde! (clockwise as seen from above Earth's north pole) which produces about 2 solar days per Venusian year! • So a solar day (noon to noon) is 116.8 Earth days. • Greenhouse effect gone crazy! • Even though a night lasts 58.4 Earth days, it is not any colder than the day side. The entire surface of Venus is at roughly a constant temperature. ~800F! • Winds: At the cloud tops are 350 km/hr, but only 0.3 km/hr at the surface.

11. Venus' landscape! Soviets landed a series of probes on Venus in the 60s-80s.

12. Venus looks rocky! Venus is made of similar compounds as the Earth. Though the clouds are ~25km thick, the surface is as bright as a cloudy day on Earth. It is clear on the surface. You can easily see to the horizon!

13. Venus is rocky planet with a cloudy 95% CO2 atmosphere. It is a massive, round planet with many seemingly dormant volcanoes. It has a surface age of 300-500 million years when the planet was entirely resurfaced in a massive event. It spins retrograde (backwards) which causes 2 solar days per year, yet the greenhouse effect keeps the entire planet at about 800oF.

16. Venus probably had about as much water as the Earth, but mostly it has been lost to space. Uncertainty- liquid on the surface or just steam in the atmosphere?

17. Quiz 3: We’ve talked about 3 planets, Earth, Mercury, and Venus. How many moons, so far? A) 0 B) 1 C) 2 D) 3 E) >10

18. Mars

20. No plate tectonics The blue areas are around 1.2 billion years old and the red ones are about 4 billion years old. The green is between 3 and 4 billion years old. Now with radiometric dating!!!!

21. Mars interior: 1) Crust- much like Earth's 2) Mantle- again much like Earth's, but a little less dense 3) Core- probably smaller than Earth's or made out of lighter material Density is 3.9 g/cc. (Earth=5.5 Moon=3.3)

22. Mars' atmosphere is 95% CO2 and only has 0.7% the pressure of Earth's.

23. Storms can completely cover Mars with dust clouds. Wind and water erosion are evident on Mars.

24. Good evidence that there was once lots of water on Mars.

25. Water is currently (occasionally) flowing on Mars' surface!

28. Moons of Mars: Phobos and Deimos

29. The Curiosity rover watches the 2 moons pass each other.

30. How did these 2 moons form? They are both small (11 and 27 km across), both not round!!! (so not massive) orbit over Mars' equator (not in the ecliptic) both orbits are nearly circular Deimos' orbit is nearly geosynchronous. Phobos' orbit is decaying and eventually Phobos will fall onto Mars...in about 40-50 million years.

31. How did these 2 moons form? Two theories: 1) they are captured asteroids. 2) Another body (stray asteroid?) passed too close to Mars and broke into bits. Over time, all the other bits (and Phobos in a few million years) have fallen onto Mars.

33. Terrestrial planets.

34. Terrestrial Planet Atmospheres Mercury- very thin, tenuous atmosphere Venus- thick 95% CO2 atmosphere Earth- thick N, O, CO, CO2 atmosphere Mars- thin 95% CO2 atmosphere

35. Terrestrial Atmospheres The original atmospheres of terrestrial planets probably all started as H, which was quickly lost to space.

36. Terrestrial Atmospheres The second atmospheres of terrestrial planets probably all started the same- mostly CO2, H2O, SO2, NH3. Why do planetologists say this? Assumes the source of the atmosphere is volcanic.

37. Terrestrial Atmospheres The second atmospheres of terrestrial planets probably all started the same- mostly CO2, H2O, SO2, NH3. So what happened? Based on mass (escape velocity) of the body, mass and temperature of the gas.

38. Terrestrial Atmospheres Mercury does not have enough mass. Also, it's too hot, so particles move faster. Atmosphere escapes too readily.

39. Terrestrial Atmospheres Venus is too hot. Liquid could not form on the surface. H2O and NH3 are reactive, so left; CO2 remains. New theory: Water vapor (possibly oceans) escaped over time from UV lights.

40. Terrestrial Atmospheres The Earth is just right! Liquid (water) formed on the surface. CO2 dissolves in water (soda) and gets deposited in soil (shale). However, without plants our oxygen would disappear. Oxygen is highly reactive, so needs to be continually replenished.

41. The Terrestrial Planets 1) The 4 planets closest to the Sun. 2) They are all objects made of rock with solid sufaces. 3) They all have thin atmospheres. 4) They have few moons.

42. Terrestrial Atmospheres Mars: Had all the right ingredients at one time. Its atmosphere probably evolved similar to ours. But without liquid water and plants to replenish the oxygen, it left the atmosphere (rusted the rocks). The atmosphere has since devolved to CO2.

43. Common properties of Terrestrial planets.

44. The Terrestrial Planets 1) The 4 planets closest to the Sun. 2) They are all objects made of rock with solid surfaces. 3) They all have thin atmospheres. 4) They have few moons.