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Phobos
#7
Oct17-04, 11:08 AM
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Quote Quote by kirkmcloren
Not only must oxygen be in a range high enough to support life -- and that means pressure as well as percentage.
Life on Earth started before the high-oxygen atmosphere we have today. The oxygen content in our atmosphere is a result (byproduct) of life.

There must be adequate water and it must be liquid.
It's true that a lot of the current exploration is focused on places with liquid water.

We also see that chemical reactions are very thermally dependent thus fevers over 107 are lethal.
107 is lethal for humans (and presumably closely related animals). Other species we know of find that downright chilly (thermophiles).
http://www.nps.gov/yell/nature/thermophiles/biopro.html

and the necessary wavelengths and intensity must be there for photo based life (plants).
Presumably, if the other conditions are right, then photosynthetic species may be able to adapt to a variety of solar outputs.

I think the odds must be 1 in billions or trillions for a suitable environment.
Life on Earth has managed to survive in a wide variety of conditions...high/low pressure, high/low temperature, aerobic/anaerobic, acidic/alkaline, high in the atmosphere/deep in the earth, lots/little water, lots/no sunlight, etc.

I think there are many chances for suitable environments, particularly for microbial-type life. The trick would be in whether life could get started. That process is not well understood.