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To answer your question directly, it is quite unlikely that planets would be habitable without already having life. It would have to be in a near-perfect condition, which would be statistically unlikely. In case of planets already having life, the existence of life provides robustness to small changes and makes habitability possible in a larger range of ...


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A basic approach would be to estimate the air-pressure at the top of the mantle. Uranus' surface gravity is a bit less than Earths, but, somewhat counter-intuitively, it's atmosphere is light enough that it's gravity increases as you move inside the planet towards the top of the mantle. (the same is true for Earth). For ballpark estimate, lets say the ...


3

Often for molecules to form in interstellar space, dust is used as a catalyst. The reason is that in typical interstellar environments, densities are so immensely low that even for just two atoms to meet, the probability is so small that formation time scales are very long. For 3+ atoms, the chance decreases rapidly. Instead, an atom can stick to a dust ...


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Yes, but probably not by a huge amount. There are two obvious ways this could happen: Direct change in atmospheric composition. If our microbe does something like eat methane and excrete longer-chain hydrocarbons, that's going to eventually change the atmosphere enough to have some effect. (If the hydrocarbons weren't already forming, they probably aren't ...


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Maybe he was thinking about the Great Oxidation Event? It was produced by early life forms (such as cyanobacteria) and, even if it caused an extinction at the time, it is thought that it allowed subsequent, more complex life forms to emerge. Can a carbon cycle exist without life? (This question might get better answers at Earth Science SE maybe?) To answer ...


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