I'm also interested in understanding the mechanisms that affect what happens to the various gases in the atmosphere over time. That is, do they get locked away in minerals, stay in the atmosphere, or get blown off into space by the solar wind? How are these mechanisms affected by the planet's mass, distance from the sun, rate of rotation, size and distance of the moon, etc. in the absence of life?

For example, according to Wikipedia's article on the Carbonate–silicate cycle, Venus lost its water by photodissociation and hydrogen escape, then Venus stopped removing carbon dioxide from its atmosphere, began instead to build it up, and experienced a runaway greenhouse effect. Is life the reason why this didn't also happen on Earth, or is there a different reason?


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On Earth, it was life that absorbed the CO2 from the atmosphere. But we cannot tell that without life there wouldn't be any other global chemical process that would do the same thing, or something absolutely different that we even cannot imagine. The global processes consist of many reactions and we cannot predict which of them would play the main roles, and in what sequence. Especially while we don't know the exact state of the ancient atmosphere. The explanation postfactum, as in the article mentioned by You, is NOT the real science, let's not forget it. It is merely pre-science. And you are trying to ask the question about the prediction of processes due to the start state - it is a serious question that only a real science can answer.

The conditions on Earth and Venus were very different from the times of the Gaian impact, our atmosphere was a thousand times weaker. There is no evidence that so much weaker atmosphere would have the same evolution. We could have an atmosphere evolution similar to Mars or something specific to our planet. Or we could be a snowball like Europe. Don't forget, that some atmospheres can have a negative greenhouse effect.


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