Download - Atmospheres/ Greenhouse Effect/ Spectroscopy
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Charles HakesFort Lewis College 1
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Charles HakesFort Lewis College 2
Atmospheres/
Greenhouse Effect/
Spectroscopy
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Charles HakesFort Lewis College 3
Logistics
• Midterm grades will be posted by Monday (faculty.fortlewis.edu/hakes_c)
• Review• Atmospheres• Planet Temperatures• Spectroscopy• Green House Effect
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Charles HakesFort Lewis College 4
Distance to Mercury
• Look up distance from Sun (A.U.) in appendix…
• Need eccentricity of Mercury. (Then check page 32.)
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Charles HakesFort Lewis College 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.)
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Charles HakesFort Lewis College 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:
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Charles HakesFort Lewis College 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.
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Charles HakesFort Lewis College 8
Figure 2.10Blackbody Curves
• Note the logarithmic temperature scale.• For linear scale, go look at the “blackbody” section of: http://solarsystem.colorado.edu/
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Charles HakesFort Lewis College 9
Wien’s Law
• The “peak” frequency of the radiation “curve” is directly proportional to the temperature of the radiator.
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Charles HakesFort Lewis College 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
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Charles HakesFort Lewis College 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
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Charles HakesFort Lewis College 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.
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Charles HakesFort Lewis College 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.
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Charles HakesFort Lewis College 14
Figure 5.7About 30% of the sunlight hitting the Earth is reflected
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Charles HakesFort Lewis College 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.
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Charles HakesFort Lewis College 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
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Charles HakesFort Lewis College 17
Earth’s Atmosphere
• 78% nitrogen• 21% oxygen - this is from living organisms• Plus Ar, CO2, H2O.• Note layers
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Charles HakesFort Lewis College 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
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Charles HakesFort Lewis College 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
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Charles HakesFort Lewis College 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
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Charles HakesFort Lewis College 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
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Charles HakesFort Lewis College 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.
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Charles HakesFort Lewis College 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…
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Charles HakesFort Lewis College 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
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Charles HakesFort Lewis College 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
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Charles HakesFort Lewis College 26
Greenhouse Effect
• Exhale
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Charles HakesFort Lewis College 27
Removing all greenhouse gasses from the Earth’s atmosphere would be good
A) True
B) False
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Charles HakesFort Lewis College 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.
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Charles HakesFort Lewis College 29
Figure 2.8Electromagnetic Spectrum
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Charles HakesFort Lewis College 30
Figure 5.7About 30% of the sunlight hitting the Earth is reflected
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Charles HakesFort Lewis College 31
Greenhouse “Strength” Contributors
• Total atmospheric pressure• Greenhouse gas percent• Greenhouse gas effectiveness
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Charles HakesFort Lewis College 32
Add Greenhouse “Strength” to Model
• Earth - 0.65• Mars - 0.077• Venus - 121.0
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Charles HakesFort Lewis College 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)
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Charles HakesFort Lewis College 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!
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Charles HakesFort Lewis College 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.
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Charles HakesFort Lewis College 36
Figure 6.8Venus, Up Close
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Charles HakesFort Lewis College 37
Figure 6.30Venus’s Atmosphere
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Charles HakesFort Lewis College 38
Discovery 5-2aThe Greenhouse Effect and Global Warming
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Charles HakesFort Lewis College 39
Discovery 5-2bThe Greenhouse Effect and Global Warming
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Charles HakesFort Lewis College 40
What gas is the most significant contributor to Earth’s greenhouse effect?
A) Methane
B) Water vapor
C) Carbon monoxide
D) Carbon dioxide
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Charles HakesFort Lewis College 41
What gas is the most significant contributor to Earth’s greenhouse effect?
A) Methane
B) Water vapor
C) Carbon monoxide
D) Carbon dioxide
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Charles HakesFort Lewis College 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?