Privileged Planet: early toxic atmosphere removed (Introduction)

by David Turell , Wednesday, November 25, 2020, 23:05 (1460 days ago) @ David Turell

It required lots of water:

https://www.newscientist.com/article/2260767-earths-early-atmosphere-may-have-been-toxi...

"When Earth was young, its surface was probably covered in a magma ocean, and the gases rising from that seething sea may have provided it with an atmosphere nearly identical to the toxic one present on Venus today.

Earth’s early magma ocean was probably created by a collision with a Mars-sized object that melted much of the young planet and created the moon. As the magma ocean cooled, some compounds would have condensed out of the molten mix and formed an atmosphere.

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"They found that this was a dense atmosphere full of carbon dioxide and with relatively little nitrogen, similar to the atmosphere on Venus today. Mars’s atmosphere has nearly the same composition, although it is much thinner.

"The fact that Earth is larger than Mars – meaning it has enough gravity to hold onto its atmosphere – and cooler than Venus allowed liquid water to remain on its surface, extracting carbon dioxide from the atmosphere and preventing the planet from going through the runaway greenhouse effect that Venus experienced to become a sweltering hellscape."

Comment: The fact our Earth surface is two-thirds water is the key. We don't look like Venus or Mars.