venus: global warming gone bad...global warming gone bad earth & venus: sister planets? venus...
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Venus: Global warming gone bad
Earth & Venus: Sister planets?
Venus Earth
Mass 5x1024 kg 6x1024 kg
a (semi-major axis)
0.7 AU 1 AU
T at surface ~750 K ~300 K
P at surface ~90 atm ~1 atm
atm composition
N2 and H2O clouds
CO2 and H2SO4 clouds
What is the boiling Temp of water?
How do we know Venus’s surface temperature?
How do we know Venus’s surface temperature?
high energy
short wavelength
“bluer”
hot
low energy
long wavelength
“redder”
cold
How do we know Venus’s surface temperature?
Earth emits light here. T=300 K the Sun emits light
here. T=6000 K Venus emits light here. T=750
How do we know what the clouds are made of?
Wavelength of light (in the infrared)
Am
ount
of l
ight
obs
erve
d ab
ove
the
atm
osph
ere
Spectrum of planet with no atmosphere
How do we know what the clouds are made of?
Wavelength of light (in the infrared)
Wavelength of light (in the infrared)
Am
ount
of l
ight
obs
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d ab
ove
the
atm
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Am
ount
of l
ight
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Wavelength at which a molecule in the atmosphere absorbs light
Spectrum of planet with no atmosphere
Spectrum of planet with atmosphere
How do we know what the clouds are made of?
(Infrared light)
How did Venus get so hot? Remember - all gases absorb light at specific wavelengths.
“Greenhouse” gases (like carbon dioxide, water and methane) like to absorb in the infrared wavelengths.
Planets emit light at infrared wavelengths (same as human bodies).
Conclusio n? “Greenhouse” gases don’t lett the heat from the planet escape.
How did Venus get so hot?
Planetary surface
A planet with no atmosphere
Solar radiation comes in
Planetary radiation goes out
How did Venus get so hot?
Planetary surface
A planet with an atmosphere
Solar radiation comes in
Planetary radiation goes out, but gets absorbed
The greenhouse gases reradiate. Some of the energy goes towards the surface.
Greenhouse gases
How do greenhouse gases get into the atmosphere?
Water: evaporation
CO2: vaporization of rocks, release from traps, vaporization of biotic material (like fossil fuels), respiration
Methane: release from traps, biology (bacteria, cows, rice)
Venus is an example of a “runaway greenhouse”.
rocks and water vaporize and release greenhouse gases
greenhouse gases heat the surface of the planet
Why was Venus hot in the first place?
Earth was also a “runaway greenhouse” at one point!
rocks and water vaporize and release greenhouse gases
greenhouse gases heat the surface of the planet
Why did the Earth cool, but Venus stay so hot?
Why did the Earth cool, but Venus stay so hot?
Ideas: Oceans?
Biology?
It probably has to do with water, but why the Earth has water and Venus doesn’t is not well
understood. It MAY be that water allowed plate tectonics to occur, and when the oceanic plates
subduct, they take CO2 with them.
The Surface of Venus
Venus’s surface can’t be viewed in visible light. The atmosphere absorbs most visible light.
Radio light reaches the surface.
Venus’s surface was mapped with RADAR.
surface
RADAR instrument
RADAR instruments can map topography.
Venus’s surface was mapped with RADAR.
smooth surface
RADAR instrument
RADAR instruments can determine roughness.
rough surface
Venus’s surface was mapped with RADAR.
Reflective surface
RADAR instrument
RADAR instruments can determine reflectivity.
Absorptive surface
Venus’s has few small craters. Why?
Venus’s has few large craters. Why?
Venus’s has few small craters. Why?
Venus’s has few large craters. Why?
Venus has a dense atmosphere.
Venus’s surface is ‘young’.
How are craters on Venus different from craters on other bodies?
Venus the moon
Venus’s surface is covered with volcanic features.
How can you tell impact craters from volcanic calderas?
What does the brightness mean in these images?
Venus’s surface is covered with volcanic features.
Few craters have been altered by lava.
What does this mean?
If lava lies over an existing crater, then the crater came first.
Venus: Take-away messages • Venus’s bulk properties (mass, size, distance from sun) are similar to Earth.
• However, Venus’s atmosphere has a lot of CO2 and therefore its surface is very hot.
• Exactly why Venus and Earth evolved in different ways is not well understood, but is probably related to water.
• Volcanism is an important process on its surface, but may not have been active recently.
• Venus’s entire surface is ‘young’, so some global resurfacing event occurred.