1. Charles Hakes
Fort Lewis College 1

2. Atmospheres/ Greenhouse Effect/ Spectroscopy
Charles Hakes
Fort Lewis College 2

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

4. Distance to Mercury Look up distance from Sun (A.U.) in appendix…
Need eccentricity of Mercury. (Then check page 32.)
Charles Hakes
Fort Lewis College 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
me for credit
(Keep running it if you want to keep the credit.)
Charles Hakes
Fort Lewis College 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:
Charles Hakes
Fort Lewis College 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.
Charles Hakes
Fort Lewis College 7

8. Figure 2.10 Blackbody Curves
Note the logarithmic temperature scale.
For linear scale, go look at the “blackbody” section of:
Charles Hakes
Fort Lewis College 8

9. Wien’s Law
The “peak” frequency of the radiation “curve” is directly proportional to the temperature of the radiator.
Charles Hakes
Fort Lewis College 9

10. You observe E-M radiation emitted from a warm dense object
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
Charles Hakes
Fort Lewis College 10

11. You observe E-M radiation emitted from a warm dense object
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
Charles Hakes
Fort Lewis College 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.
Charles Hakes
Fort Lewis College 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.
Charles Hakes
Fort Lewis College 13

14. Figure 5.7 About 30% of the sunlight hitting the Earth is reflected
Charles Hakes
Fort Lewis College 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.
Charles Hakes
Fort Lewis College 15

16. To Atmosphere or Not Primary atmosphere Secondary 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
Charles Hakes
Fort Lewis College 16

17. Earth’s Atmosphere 78% nitrogen
21% oxygen - this is from living organisms
Plus Ar, CO2, H2O.
Note layers
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Fort Lewis College 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
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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.
Charles Hakes
Fort Lewis College 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…
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 25

26. Greenhouse Effect
Exhale
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Fort Lewis College 26

27. Removing all greenhouse gasses from the Earth’s atmosphere would be good
A) True
B) False
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Fort Lewis College 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.
Charles Hakes
Fort Lewis College 28

29. Figure 2.8 Electromagnetic Spectrum
Charles Hakes
Fort Lewis College 29

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

31. Greenhouse “Strength” Contributors
Total atmospheric pressure
Greenhouse gas percent
Greenhouse gas effectiveness
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Fort Lewis College 31

32. Add Greenhouse “Strength” to Model
Earth
Mars
Venus
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Fort Lewis College 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)
Charles Hakes
Fort Lewis College 33

34. Planet Temperatures Much better agreement!
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!
Charles Hakes
Fort Lewis College 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.
Charles Hakes
Fort Lewis College 35

36. Figure 6.8 Venus, Up Close
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Fort Lewis College 36

37. Figure 6.30 Venus’s Atmosphere
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Fort Lewis College 37

38. Discovery 5-2a The Greenhouse Effect and Global Warming
Charles Hakes
Fort Lewis College 38

39. Discovery 5-2b The Greenhouse Effect and Global Warming
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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?
Charles Hakes
Fort Lewis College 42