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Let's say you have a planet pretty similar to Earth. It resembles Earth at around the time life is thought to have begun - except that it's a bit less hostile to life. The atmosphere is mainly carb...
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#1: Attribution notice removed
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System
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2020-06-01T14:13:38Z (over 4 years ago)
Source: https://worldbuilding.stackexchange.com/a/2758 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/