Quote:
Originally Posted by OICURMT
Why would we have to concentrate on Oxygen? Are we, as a humans, stating that all intelligent life *MUST* breath oxygen? What about Groot? "He" takes in CO2 and exhales oxygen! Maybe we should concentrate on CO2, albeit difficult as it's a by-product of volcanism.
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The reasoning is that planetary atmospheres form with a reducing atm because that's what you get when you condense a proto-planetary disc. On Earth the oxygen is wholly a product of photosynthesis and so proves that the Earth is inhabited (at least by blue-green algae). I understand that there may be planets where chemical energy is obtained by other means but if you see oxygen there is life.
Could we detect the oxygen in Earth's atm from the distance of an exoplanet? I suspect not. So if we couldn't detect life on Earth from several light years distance why would we think we can detect it on an exoplanet?
Quote:
Originally Posted by deanm
As a molecular geneticist, the fundamental basis of life on earth was the evolution of self-replicating molecules which contain & propagate information.
That's the hard part, but a lot of chemistry can happen over a few billion years.
Once you have self-replicating molecules, the subsequent development of cellular structures, then multicellularity, is pretty straightforward.
So *life* can readily evolve. However, intelligent life is a different proposition.
Dean
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My understanding is that the development of life might be pretty 'easy' but developing photosynthesis may be the big stumbling block. I recall hearing that the evolution of photosynthesis is very unlikely. Something about it requiring the appearance of two unlikely chemical pathways at the same time. This explains why things like vision, hearing and all forms of locomotion have evolved multiple time but photosynthesis only evolved once. It could well be that there are many planets where rudimentary life has developed but hasn't progressed much because there is no mechanism to capture solar energy. So they may have a few 'worms' hanging around deep sea vents but no phyto-plankton in the oceans, no land plants and no higher organisms harvesting the trapped solar energy.
Of course people will argue that alien life may use a different chemistry and I accept that. However the chemical pathways should at least be viable. Mythical beings who are powered by endothermic reactions are just that - mythical. In the meanwhile we should consider what we can predict based on the biochemistry we know.
BTW were you bored today Alex?? Thought the pot needed some stirring?