Chapter 9: Atmospheres of the Terrestrial Planets

1. Chapter 9:Atmospheres of the Terrestrial Planets

2. Terrestrial Atmospheres Only Earth, Venus and Mars have a substantial atmosphere. The Moon and Mercury only have traces of gases around them.

3. The primary atmosphere was mostly H and He H and He were captured during formation. Since all the terrestrial worlds have small masses, their gravity wasn’t strong enough to hold on to these gases and they escaped to space. Only massive planets like Jupiter can hold on to a primary atmosphere.

4. Venus, Earth and Mars are on their 2nd atmosphere after having lost their first one Play with Gas Retention Simulator on ClassAction website in Resources Menu

5. Most secondary atmospheres come from volcanoes and comets The gases are mostly carbon dioxide, carbon monoxide, sulfur dioxide, water vapor and nitrogen

6. The Greenhouse Effect is important on Venus, Earth and Mars A balance is established between the incoming energy and the outgoing energy. Since blackbody radiation depends on temperature, the balance point depends on the temperature of the planet

7. On Venus a runaway greenhouse effect baked the planet. The balance point is almost 750 K The clouds of Venus give it a very high albedo (0.65). It’s temperature would be below freezing if not for the greenhouse effect. The thick atmosphere of CO2causes an extreme greenhouse effect.

8. The atmosphere of Mars is too thin to have much of a greenhouse effect Like Venus, it’s mostly CO2 but it’s so thin there just isn’t much gas to absorb infrared radiation from the ground

9. Earth’s atmosphere managed to lock away almost all the CO2 If all the CO2 locked up in Earths’ rocks were released, Earths’ atmosphere would be 98% CO2. As it is, CO2 Earths’ atmosphere makes up less than 0.04% of

10. How did our atmosphere get this way? Most of the CO2, CO and SO2 got locked up by the oceans as rocks like limestone. That left mostly nitrogen and smaller amounts of CO2. Life created the oxygen.

11. Earth’s Atmosphere is layered like an onion The layers are due to how the temperature changes with altitude. Mars and Venus don’t show the same kind of layering.

12. The way temperature changes is due to energy transport In the stratosphere and thermosphere energy is absorbed directly from the Sun so the temperature increases with altitude In the troposphere convection is driven by heat from the ground so the temperature decreases with altitude

13. Beyond the atmosphere, Earth has a Magnetosphere The magnetosphere shields the Earth’s atmosphere from the solar wind.

14. When particles trapped in the magnetic field collide with the upper atmosphere we get auroras

15. The weak or non-existent magnetic fields of Venus and Mars lead to strong erosion by the solar winds The stronger gravity of Venus has been able to hold on to its atmosphere but Mars lost most of its atmosphere to erosion by the solar wind.

16. Just as in the interior of the planets, convection is important to atmospheres Rotation and the Coriolis effect are also important

17. Convection in the upper atmosphere is influenced by the Coriolis Effect

18. Winds in the upper atmosphere of Venus also show strong convection

19. Despite its thin atmosphere, convection on Mars is important to its global winds

20. Convection is also important on a smaller scale

21. Thunderstorms are driven by convection Static electricity developed by the convection creates lightning

22. Mars also shows convection in its clouds and storms

23. Martian Global Dust Storm

24. Dust Storm Erupting out of North Pole of Mars

25. Dust Devils are small scale convection Dust devils on Mars can be several kilometers tall

26. Dust devils are found in dry places on Earth

27. Weather on Venus?

28. The ESA’s Venus Express is now taking a close look at the atmosphere of Venus

29. Is mankind changing Earth’s atmosphere? Man?

30. Each spring in Antarctica a hole develops in the ozone layer

31. The Ozone Hole changes from year to year

32. Ozone depletion is caused by CFC’s CFC’s are Chlorofluorocarbon molecules which are man made compounds. They do not occur naturally

33. The solution: stop using CFC’s The 1987 Montreal Treaty gradually reduces the production and consumption of CFC’s worldwide

34. Is the Ozone Hole getting worse or better?

35. Our actions have led to an increase in the level of a number of greenhouse gases Unfortunately, we can’t stop producing these gases as easily as we stopped producing CFC’s

36. Deforestation removes the trees that remove CO2 The cut trees are usually burned which adds more CO2 to the atmosphere

37. There is a direct relationship between the level of CO2 and the global average temperature

38. Our actions may be keeping us from another ice age

39. All climate models predict that it will get warmer

40. We are performing an experiment on our atmosphere. What the outcome will be we don’t yet know