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History
of Venus' Atmosphere
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Similar orbit and planet
size to Earth, probably started the same
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Sun may have been 70% cooler
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Venus may have had water
oceans
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Made water clouds, which
helped trap heat (greenhouse effect on Venus and Earth)
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On Earth, life started Early,
plants absorbed CO2, gave off Oxygen, Ozone layer formed
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Venus closer to sun, a little
warmer, not rotating as fast...
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On Venus, no life, or life
didn't make it, lots of CO2 in atmosphere, no Ozone
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As Sun warmed up, Venus got
hotter
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oceans started to evaporate
more
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more clouds
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more greenhouse effect
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...runaway greenhouse effect
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Evaporated all water on Venus
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At top of atmosphere, sunlight
breaks water up
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Hydrogen escapes (too little
gravity--same on Earth)
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High temperatures bake CO2
out of rocks
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CO2 contributes
to greenhouse effect, replaced water as reflecting blanket
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On Earth, CO2
absorbed by plants and chemical reactions with water and rocks that
form carbonate rocks like limestone
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Plate tectonics on Earth
can expose fresh rock
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Formation of Himalayas may
have caused last ice age
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Venus has no plate tectonics
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Earth has life, Venus does
not
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