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Atmospheres/ Greenhouse Effect/ Spectroscopy

Atmospheres/ Greenhouse Effect/ Spectroscopy. Logistics. Midterm grades will be posted by Monday ( faculty.fortlewis.edu/hakes_c ) Review Atmospheres Planet Temperatures Spectroscopy Green House Effect. Distance to Mercury. Look up distance from Sun (A.U.) in appendix…

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Atmospheres/ Greenhouse Effect/ Spectroscopy

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  1. 1

  2. Atmospheres/ Greenhouse Effect/ Spectroscopy 2

  3. Logistics • Midterm grades will be posted by Monday (faculty.fortlewis.edu/hakes_c) • Review • Atmospheres • Planet Temperatures • Spectroscopy • Green House Effect 3

  4. Distance to Mercury • Look up distance from Sun (A.U.) in appendix… • Need eccentricity of Mercury. (Then check page 32.) 4

  5. Seti@home Notes • Credit is available if you join! • link is on my home page • download the software • install and run - you will have to “connect” to the SETI project after you install • after completing a work unit, join the FLC group • email me for credit • (Keep running it if you want to keep the credit.) 5

  6. Review • What was the most important thing you learned? • Albedo is how much light gets reflected. • Earth has an albedo of 0.3 • Albedo is not related to libido. • For any given temperature, the lighter stuff moves faster. • Wien’s law: 6

  7. Blackbody Radiation (Review!) • Higher temperature bodies radiate energy in shorter wavelength radiation. • The Sun radiates at visible wavelengths • The Earth (and other planets) radiate at much longer wavelengths. 7

  8. Figure 2.10Blackbody Curves • Note the logarithmic temperature scale. • For linear scale, go look at the “blackbody” section of: http://solarsystem.colorado.edu/ 8

  9. Wien’s Law • The “peak” frequency of the radiation “curve” is directly proportional to the temperature of the radiator. 9

  10. You observe E-M radiation emitted from a warm dense object. The most radiation appears to be emitted at 5.8x10-4 cm. What temperature is the object? A) 400 K B) 500 K C) 600 K D) 700 K 10

  11. You observe E-M radiation emitted from a warm dense object. The most radiation appears to be emitted at 5.8x10-4 cm. What temperature is the object? A) 400 K B) 500 K C) 600 K D) 700 K 11

  12. Planet Temperature • Go to Solar System Collaboratory on EVM “physics” page. • A planet must balance absorbed light and radiated light to get a temperature. • Light intensity decreases with distance. (another 1/r2 law) • Farther from the sun, the absorbed light is less. 12

  13. Planet Temperature • Go to Solar System Collaboratory on EVM “physics” page. • A planet must balance absorbed light and radiated light to get a temperature. • Light intensity decreases with distance. (another 1/r2 law) • Farther from the sun, the absorbed light is less. • Go to Solar System Collaboratory on planet temperature page. 13

  14. Figure 5.7About 30% of the sunlight hitting the Earth is reflected 14

  15. To Atmosphere or Not • Once you know a planet’s temperature you can see if it will have an atmosphere, and how that atmosphere can affect a planet’s temperature. • Compare kinetic energy of molecules with “escape velocity” from the planet. • Light molecules (of a given temperature T) move faster than heavy molecules of the same temperature. • A small fraction will always escape. 15

  16. To Atmosphere or Not • Primary atmosphere • What a planet had after formation • Mostly H, He - almost all gone from the terrestrial planets (never really was here) • Secondary atmosphere • Heavier molecules N2, CO2 From rock outgassing • H2O from outgassing and comet impacts. • O2 from Life 16

  17. Earth’s Atmosphere • 78% nitrogen • 21% oxygen - this is from living organisms • Plus Ar, CO2, H2O. • Note layers 17

  18. Which will have the greatest effect on a planet’s temperature? A) doubling a planet’s distance to the sun B) doubling a planet’s albedo C) doubling a planet’s mass D) doubling a planet’s rotation rate 18

  19. Which will have the greatest effect on a planet’s temperature? A) doubling a planet’s distance to the sun B) doubling a planet’s albedo C) doubling a planet’s mass D) doubling a planet’s rotation rate 19

  20. Compared to Earth, the Moon undergoes temperature extremes because? A) It orbits the Earth, and therefore gets both closer and farther from the Sun than Earth B) It has no atmosphere C) It rotates very slowly D) Both B and C 20

  21. Compared to Earth, the Moon undergoes temperature extremes because? A) It orbits the Earth, and therefore gets both closer and farther from the Sun than Earth B) It has no atmosphere C) It rotates very slowly D) Both B and C 21

  22. Planet Temperatures • Go to Solar System Collaboratory to see planet temperatures page. • Look at fact sheet • Earth - (albedo 0.3) 288 K • Moon - (albedo 0.07) 280 K • Mars - (albedo 0.2) 218 K • Venus - (albedo 0.8) 730 K • Compare model to fact sheet. • Review model - distance and albedo. 22

  23. Planet Temperatures • Compare the model to the fact sheet. • Earth - (albedo 0.3) 288 K (model 255 K) • Moon - (albedo 0.07) 280 K (model 273 K) • Mars - (albedo 0.2) 218 K (model 214 K) • Venus - (albedo 0.8) 730 K (model 219 K) • Model with fast-rotating planet with variable albedo predicted temperatures that were too low. • Something is missing from the model… 23

  24. What is Missing from the model? A) Realistic rotation rates for the planets B) Geothermal Energy C) Distance from the Sun D) Something else important 24

  25. What is Missing from the model? A) Realistic rotation rates for the planets B) Geothermal Energy C) Distance from the Sun D) Something else important 25

  26. Greenhouse Effect • Exhale 26

  27. Removing all greenhouse gasses from the Earth’s atmosphere would be good A) True B) False 27

  28. Greenhouse Effect • Visible light comes in though the atmosphere and heats the ground. • Re-radiating infrared light can’t get out because the atmosphere is partially opaque. • Greenhouse gasses must have at least 3 atoms in each molecule to absorb effectively in the IR. • Note - “real” greenhouses merely stop convection from carrying away heat. 28

  29. Figure 2.8Electromagnetic Spectrum 29

  30. Figure 5.7About 30% of the sunlight hitting the Earth is reflected 30

  31. Greenhouse “Strength” Contributors • Total atmospheric pressure • Greenhouse gas percent • Greenhouse gas effectiveness 31

  32. Add Greenhouse “Strength” to Model • Earth - 0.65 • Mars - 0.077 • Venus - 121.0 32

  33. Planet Temperatures • Compare the model to the fact sheet. • Earth - (A 0.3, GH 0.65) 288 K (model 289 K) • Moon - (albedo 0.07) 280 K (model 274 K) • Mars - (albedo 0.2) 218 K (model 218 K) • Venus - (albedo 0.8) 730 K (model 730 K) 33

  34. Planet Temperatures • Compare the model to the fact sheet. • Earth - (A 0.3, GH 0.65) 288 K (model 289 K) • Moon - (albedo 0.07) 280 K (model 274 K) • Mars - (albedo 0.2) 218 K (model 218 K) • Venus - (albedo 0.8) 730 K (model 730 K) • Much better agreement! 34

  35. Greenhouse Runaway • On Venus, the temperature was just high enough to keep most of the water in the atmosphere. • CO2 could not be absorbed into the water, and eventually trapped in the surface rocks. • If all Earth’s CO2 were released into the atmosphere, it would be ~98% CO2, 2% N2 and the pressure would be ~70x current. 35

  36. Figure 6.8Venus, Up Close 36

  37. Figure 6.30Venus’s Atmosphere 37

  38. Discovery 5-2aThe Greenhouse Effect and Global Warming 38

  39. Discovery 5-2bThe Greenhouse Effect and Global Warming 39

  40. What gas is the most significant contributor to Earth’s greenhouse effect? A) Methane B) Water vapor C) Carbon monoxide D) Carbon dioxide 40

  41. What gas is the most significant contributor to Earth’s greenhouse effect? A) Methane B) Water vapor C) Carbon monoxide D) Carbon dioxide 41

  42. Three Minute Paper • Write 1-3 sentences. • What was the most important thing you learned today? • What questions do you still have about today’s topics? 42

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