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A comment on The Earth-Twin Planet That Nobody Talks About. Parent comment

Re:The Earth-Twin Planet That Nobody Talks About by twic on Sunday October 18, 2015 @06:32PM (#10410107)
Close! Earth's atmosphere was much the same as Venus's up to four billion years ago. But it seems that what made the difference was the carbonate cycle:

https://en.wikipedia.org/wiki/Carbonate%E2%80%93silicate_cyc...

That article blames the difference on the temperature. Elsewhere, i've seen the presence of water oceans being implicated. Either way, i don't think life was the mechanism at that point. Life didn't really have much of an impact for another billion years or two:

https://en.wikipedia.org/wiki/Great_Oxygenation_Event

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Re:The Earth-Twin Planet That Nobody Talks About by jerf on Sunday October 18, 2015 @07:12PM (#10410259)
Partially in response to your other post as well, I've also seen it hypothesized that the collision that produced Earth's moon stripped away most of Earth's atmosphere, the idea being that Venus' atmosphere may actually be the "normal" atmosphere for an Earth-sized planet.

As usual, the core problem is just that our data set is too darned small. Is our Solar System mostly normal? Is our Solar System a bizarre, billions-to-one odds freak case? We don't really know.

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