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takyon writes:

Earth's Moon Could Have Been Habitable 3.5 Billion Years Ago

A new paper by Ian Crawford from the University of London and myself [Dirk Schulze-Makuch], just published in the journal Astrobiology [open, DOI: 10.1089/ast.2018.1844] [DX], claims that Earth's Moon might have been habitable about one billion years after its formation, when pools of liquid water may have existed on the lunar surface. Today, of course, the Moon has no atmosphere and no liquid water. It's uninhabitable and certainly lifeless. But 3.5 billion years ago, a billion years after it formed, the lunar environment was quite different.

During this period of extreme outgassing from lunar magma, the Moon is estimated to have had an atmospheric pressure of 10 millibar, or one percent of Earth's current atmosphere. This is thicker than the current atmosphere on Mars, and would have been substantial enough for liquid water to pool on the lunar surface, perhaps for many millions of years.

Combine this with recent findings that lunar rocks are more water-rich than previously thought [DOI: 10.1038/ngeo2845] [DX], and we can hypothesize that lakes, even an ocean, could have stably existed on the Moon for a substantial amount of time. There is also evidence that the early Moon had a magnetic field [DOI: 10.1016/j.icarus.2010.08.012] [DX], which might have partially protected its surface from solar and cosmic radiation. This would have resulted in a temporarily habitable world, at a time when life on Earth had already gained a foothold.

Also at Motherboard and Astronomy Magazine.

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