Mars had a Great Oxygenation Event, just like Earth did.

  • #1
jim mcnamara
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Mars underwent a biologically induced change (assumption -- via photosynthesis) to the atmosphere billions of years ago. Rock strata were identified that are evidence of an earlier atmosphere, that is different from what came later. The more recent atmosphere oxidized iron in most of the surface rocks to red.

So, if there are ancient mineral deposits that only form in reducing atmospheres under long term conditions, and now those conditions have changed to oxidative, then something changed it. The only example we have is Earth. Our Great Oxidation Event about 2+ billion years ago.

More research is going to be needed to verify this result. One result is good, lots of backup is really required for this kind of report.

“Anoxic chemical weathering under a reducing greenhouse on early Mars” by J. Liu, J. R. Michalski, W. Tan, H. He, B. Ye and L. Xiao, 11 February 2021, Nature Astronomy.
DOI: 10.1038/s41550-021-01303-5
 
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Mars underwent a biologically induced change (assumption -- via photosynthesis) to the atmosphere billions of years ago.

The abstract says something different:

"Although for different reasons than on Earth, Mars underwent an oxidation event of its own in the late Noachian that forever changed the geological path of the planet."


I didn't read the the full article because it's behind a paywall. Does it really refer to a biologically induced change?
 
  • #3
jim mcnamara
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@DrStupid
Good point. My assumption - not their assumption. The paper does not support proof of life on Mars.

However, massive amounts of oxygen are clearly tied up in surface rocks. It had to come from somewhere. Most likely candidate is ##CO_2##. Synthesizing and testing an alternate viable scenario is difficult. Even assuming biology by taking the simplest known choice (so-called Occam's Razor) is going to require lots of research. And I do not know if the paper itself will withstand futher investigations.
See: https://www.merriam-webster.com/dictionary/Occam's razor
Another hypothesis (model) for oxygen, before huge amounts of surface water was confirmed on Mars.:
https://www.nature.com/news/2004/040503/full/news040503-6.html
 
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  • #4
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Most likely candidate is ##CO_2##.
Why not ##H_2O##? Water vapour and water ice can be converted into oxidants like ##O_2## and ##H_2O_2## by photochemical reactions. That was not sufficient for a global change of redox state on Earth but Mars is different. The lack of a magnetic field exposes the atmosphere to the solar wind and cosmic radiation, the lower gravity makes it easier for ##H_2## to escape into space and due to lower temparatures there is a higher probability for snowball events which allow for accumulation of large amounts of ##H_2O_2##.
 
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The paper seems more about proving Mars was in a reduced state than proving there was the equivalent of great oxidation event. As they noted, the surface of Mars is quite oxidized now, probably by photo-oxidation over billion of years.
 
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  • #6
I believe Mars did have an oxygenated atmosphere like earth and that it's disappearance was not biological which would occur over time but suddenly and completely due to something like being in a bad position when a solar flare erupted.
 
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pinball1970
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