 | In Response To: Re: Xenobiology question (Steve Levinson)
I should probably point out that oxygen-rich atmospheres are not entirely a natural phenomenon - at least not in the sense of inert matter. The early earth contained an atmosphere rich in nitrogen and carbon dioxide. Life as we know it would not have existed had it not been for the evolution of chlorophil in early bacteria. The ability of some bacteria to directly extract energy from sunlight and convert it to fuel resulted in an explosion of algae, pouring tons of oxygen into the atmosphere. The evolution of some of these to effectively reverse the process, using the now readily available oxygen to convert that fuel back into energy more efficiently than with anaerobic matabolism, led eventually to the mitochondria that made us possible. Now imagine a situation where the evolution of chlorophil never happened, perhaps where the seas were devoid of water, perhaps containing something like liquid methane or hydrocarbons. The entire metabolic paradigm would be different from ours. Very interesting possibilities . . .
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