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400 million years to build a planet?
I'm stuck writing up a planet for another science fiction setting that is easily inhabitable by humans (Earth-like ecosystem) and has native life has reached mammalian-ish levels of sophistication.

Problem: the planet is only 400 million years old. I can't change that, nor can I invoke artificial intervention. The planet is not terraformed, nor are there any ancient aliens I can invoke.

So, never mind the probabilities, is 400 million years enough time for a terrestrial planet to solidify and produce an oxygen atmosphere, assuming life started early?

If I'm reading the history of Earth article on wiki correctly, it takes some 10 to 20 million years to form a crust and oceans. However, Earth's environment got more stable around the beginning of the Archean 500 million years after formation. The biggest spike in oxygenation happened in a 300 million year period. Most multi-cellular life developed in a 500 million year period...actually, it was pretty sophisticated within 250 million years of the Cambrian explosion. So, it LOOKS like a planet could get habitable in a 400 million year period, but I'd like the story to make sense.

I'm also constrained by canon to a 0.92G surface gravity, 16% land area, and Earth-like atmospheric pressure and composition, but I can vary density, diameter, and planetary composition within those limits if it helps.
Mike Miller, Materials Engineer

"Everbody's always in favor of saving Hitler's brain, but when you put it in the body of a great white shark, oh, suddenly you've gone too far." -- Professor Farnsworth, Futurama

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400 million years to build a planet? - by Cray - 09-21-2015, 10:40 AM

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