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Planetary Atmospheres. Greenhouse Effect. 90 atmospheres!. Planetary Atmospheres. Greenhouse Effect. 240 watts/m 2 in. 240 watts/m 2 out. Small fraction escapes into space. 50% reflected by clouds and surface. CO 2 H 2 0. Planetary Atmospheres. Greenhouse Effect.

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planetary atmospheres
Planetary Atmospheres
  • Greenhouse Effect

90 atmospheres!

planetary atmospheres4
Planetary Atmospheres
  • Greenhouse Effect
  • 240
  • watts/m2
  • in
  • 240
  • watts/m2
  • out

Small fraction

escapes into

space

  • 50% reflected by
  • clouds and surface
  • CO2
  • H20
planetary atmospheres5
Planetary Atmospheres
  • Greenhouse Effect

Energy Out

Energy In

200 energy units

stored

in equilibrium

100 energy units

100 energy units

100% gate

50% gate

planetary atmospheres6
Planetary Atmospheres
  • Greenhouse Effect

Energy Out

Energy In

10, 000 energy units

stored

in equilibrium

100 energy units

100 energy units

100% gate

1% gate

planetary atmospheres7
Planetary Atmospheres
  • Greenhouse Effect
slide8

ConcepTest!

Frosts are most likely to happen on clear nights rather than cloudy nights. This is because

A) Cloudy nights lead to falling snow

B) Clouds are not transparent to optical light

C) More infrared light can be radiated through clear skies

D) Snow and frost reflect rather than absorb visible light

planetary evolution
Planetary Evolution
  • Essential Idea
      • Evolution of both geology and atmospheres
      • driven by energy flow from planetary cores
planetary evolution10
Planetary Evolution
  • Essential Idea
      • Recall
        • Amount of residual thermal energy stored in planet
        • depends on planet volume (amount of material)
        • Rate of energy loss depends on planet surface area
        • Small planets go dormant sooner
planetary evolution11
Planetary Evolution
  • Comparative Planetology - Earth and Mars
      • MarsEarth
      • Dormant volcanos Active volcanos
planetary evolution12
Planetary Evolution
  • Comparative Planetology - Earth and Mars
      • MarsEarth
      • Dormant volcanos Active volcanos
      • Water in past Water at present
planetary evolution13
Planetary Evolution
  • Comparative Planetology - Earth and Mars
      • MarsEarth
      • Dormant volcanos Active volcanos
      • Water in past Water at present
      • Thin CO2 atmosphere N2/O2 atmosphere
      • (0.01 atmos) (1 atmos)
    • Note: Liquid water would not survive on Mars today -
    • it would boil due to low atmospheric pressure.
    • So if liquid water in past, must also have been
    • substantial atmosphere and greenhouse effect in past
    • Active volcanoes could have provided such an atmosphere
planetary evolution14

Plate tectonics is critical to Earth atmosphere

Planetary Evolution
  • Comparative Planetology - Earth

Ozone O3

washed out with H20 rain

planetary evolution15
Planetary Evolution
  • Comparative Planetology - Earth

Ozone O3

washed out with H20 rain

Life is critical to oxygen in Earth atmosphere

slide16

ConcepTest!

If plate tectonics on the Earth were to end, you would expect the temperature of the Earth’s surface to

A) Increase

B) Change little or not at all

C) Decrease

planetary evolution17
Planetary Evolution
  • Comparative Planetology - Mars at 1 billion yr
  • (end of geologic activity)

UV

O,C

H2O rain washes CO2 into surface - permanently

Greenhouse effect reduced

Colder temperatures lead to enhanced rain, less gaseous CO2, less greenhouse

(“Runaway Icehouse Effect”)

Most CO2 in carbonate rocks, most H2O in permafrost

UV sunlight breaks up molecules and provides energy of escape

planetary evolution18
Planetary Evolution
  • Comparative Planetology - Mars at 4.5 billion yr

Recent liquid water?

planetary evolution19
Planetary Evolution
  • Comparative Planetology - Earth and Venus
      • VenusEarth
      • Active volcanos Active volcanos
planetary evolution20
Planetary Evolution
  • Comparative Planetology - Earth and Venus
      • VenusEarth
      • Active volcanos Active volcanos
      • Vesc = 10.3 km/sec Vesc = 11.2 km/sec
planetary evolution21
Planetary Evolution
  • Comparative Planetology - Earth and Venus
      • VenusEarth
      • Active volcanos Active volcanos
      • Vesc = 10.3 km/sec Vesc = 11.2 km/sec
      • CO2 atmosphere N2/O2 atmosphere
      • (90 atmos) (1 atmos)
planetary evolution22
Planetary Evolution
  • Comparative Planetology - Earth and Venus
      • VenusEarth
      • Active volcanos Active volcanos
      • Vesc = 10.3 km/sec Vesc = 11.2 km/sec
      • CO2 atmosphere N2/O2 atmosphere
      • (90 atmos) (1 atmos)
      • Dry (10-4 Earth H20) Water at present
    • Note: Based on measurements of deuterium (“heavy water”)
    • Venus had substantially more water in the past
    • Consistent with outgassing from volcanos and large
    • escape velocity
planetary atmospheres23

Temperature

Light from Sun

or CO2, H2O

CO2, H2O

from rocks

from oceans

Planetary Atmospheres
  • Comparative Planetology - Venus
      • Suppose Venus were “Earth-like” (liquid water) and …

“Runaway Greenhouse Effect”

planetary atmospheres24
Planetary Atmospheres
  • Runaway Greenhouse Effect
      • once RGE begins …

Escape

H2

UV

from

Sun

H20 in

atmos

RGE

+

O2

Surface

Compounds

Irreversible!!

planetary atmospheres25
Planetary Atmospheres
  • Comparative Planetology - Venus at 4.5 billion yr
planetary evolution summary
Planetary Evolution - Summary

Earth

77% N2, 21% O2

15 oC

1 atmosphere

Mars

95% CO2

-50 oC

0.01 atmospheres

Venus

96% CO2

470 oC

90 atmospheres

Mercury

Trace of

He, Na, O

Moon Trace of He, Na, Ar

planetary evolution summary27

Atmospheric Evolution

    • Moon, Mercury - low escape velocity, hot, atmos escapes
    • Venus RGE, massive CO2 atmos
    • Earth CO2, H2O , N2 N2, O2
    • Mars Runaway Icehouse,
    • thin CO2 atmos
Planetary Evolution - Summary
  • Geological Evolution
    • Mercury, Moon - smallest radii => dormant, cratered
    • Mars - active for 109 yr, now dormant (shield volcanoes)
    • Venus - current volcanos (shield volcanoes)
    • Earth - convection => plate tectonics