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What events could have to happen to Mars (which is thought to once look like Earth) that may have depleted the atmosphere and erase all proof of life ever existing at least on the surface?

I know an asteroid could melt the planet but could there have been an event that could wipe the surface while leaving deposits under the ground intact?

There is no proof that Mars melted but there is proof that there at least was oceans.

http://en.yibada.com/articles/18182/20150309/red-planet-once-held-large-shallow-ocean-mean-positive-signs.htm

Where did Mars water go?

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    $\begingroup$ "Tell me... would it be greatly improved by an oil pipeline?" - Dr Manhattan $\endgroup$ – antispinwards Mar 9 '19 at 19:12
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    $\begingroup$ This sounds more like hypothetical worldbuilding questions than astronomy questions. Still, a Theia-like impact would likely erase all evidence by re-melting the planet and carbonizing all organics (oil included). $\endgroup$ – Anders Sandberg Mar 9 '19 at 21:12
  • $\begingroup$ I'd be shocked if there weren't a molecule or two of oil around some of the methane vents. Vents which IIRC, have not been found, except as occasional mysterious plumes. $\endgroup$ – Wayfaring Stranger Mar 11 '19 at 16:01
  • $\begingroup$ @Muze - My comment made more sense with the original version of the question, since it was about Earth rather than Mars. $\endgroup$ – Anders Sandberg Mar 11 '19 at 20:47
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Planet solidifying.

No molten core iron -> no magnetosphere -> solar wind strips atmosphere.
Without atmosphere to cycle in exposed water also leaves.

Why did Mars freeze solid & Earth has not (yet).

  • is further from sun
  • smaller means less volume to hold heat
  • Earth may have the iron cores from two planets (moon forming impact)
  • Radioactive decay?

On oil, possibly.
If there was life there and it colonized the land and it found it needed to create a scaffolding structure to compete for photons such as ligand as happened here, and there were several hundred millions years until other life there figured out how to digest those ligands then there would be a layer there like our Carboniferous era in which a large amount of carbon is sequestered underground.

But chances are vanishingly slim.
If there was life there it most likely

  • recycled carbon just as we have here for all time except that little blip* after trees showed up and before bacteria figured out how to digest them.
  • did not survive long enough to need to compete for photons by growing very tall

(*) 300,000,000 / 4,300,000,000 is about 1/14th of life on earth's history.

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  • $\begingroup$ Very nice answer $\endgroup$ – Muze the good Troll. Apr 15 '19 at 2:48
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    $\begingroup$ "is further from the sun" -- this is actually irrelevant, because the Earth's core is not appreciably heated by the sun. (It's still molten because of residual heat from the Earth's formation and from radioactive decay.) $\endgroup$ – Peter Erwin Apr 16 '19 at 11:33
  • $\begingroup$ granted distance is of very low relevance. $\endgroup$ – tomc Apr 18 '19 at 18:43
  • $\begingroup$ Also note that Mars likely lost any ocean it may have had a couple of billion year before Earth made its way into our carboniferous (oil producing) interval. $\endgroup$ – tomc Apr 18 '19 at 18:47

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