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Solar
energy incident on the Earth |
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= total amount of solar
energy can be absorbed by Earth |
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= (Solar constant) x (Shadow Area) |
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= S x p R2Earth |
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Distance
from the Sun |
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Albedo |
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Greenhouse effect |
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On Venus
è 510°K (very large!!) |
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On
Earth è 33°K |
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On
Mars è 6°K (very small) |
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Venus is
too close to the Sun |
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Venus
temperature is very high |
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Very
difficult for Venus’s atmosphere to get saturated in water vapor |
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Evaporation keep on bringing water vapor into Venus’s
atmosphere |
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Greenhouse effect is very large |
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A “run
away” greenhouse happened on Venus |
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Water
vapor is dissociated into hydrogen and oxygen |
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Hydrogen
then escaped to space and oxygen reacted with carbon to form carbon dioxide |
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No water
left on Venus (and no more chemical weathering) |
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Mars is
too small in size |
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Mars had no large internal heat |
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Mars lost all the internal heat quickly |
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No tectonic activity on Mars |
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Carbon can not be injected back to the
atmosphere |
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Little greenhouse effect |
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A very cold Mars!! |
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The larger the solar zenith angle, the weaker
the insolation, because the same amount of sunlight has to be spread over a
larger area. |
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Polarward heat flux is needed to transport
radiation energy from the tropics to higher latitudes. |
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