Oxygen is not definitive evidence of life on habitable extrasolar planets

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Discussion Overview

The discussion centers on the role of oxygen as a potential biomarker for life on habitable extrasolar planets. Participants explore the implications of recent research suggesting that abiotic processes could produce significant amounts of oxygen, challenging the assumption that its presence necessarily indicates biological activity. The scope includes theoretical implications for astrobiology and the search for extraterrestrial life.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants note that the traditional view held that oxygen in a planet's atmosphere must originate from biological processes, particularly photosynthesis.
  • Others argue that recent research proposes the possibility of abiotic sources of oxygen, suggesting that its presence does not definitively indicate life.
  • A participant highlights the distinction between necessary and sufficient conditions for life, suggesting that the presence of oxygen is necessary but not sufficient for confirming biological activity.
  • Another participant references geological processes, such as the stability of iron oxides in mantle rocks, as potential abiotic sources of free oxygen in planetary atmospheres.
  • One viewpoint suggests that while abiotic processes can produce oxygen, this does not diminish the plausibility of oxygen being a strong marker of photosynthetic life, especially in environments conducive to organic chemistry.

Areas of Agreement / Disagreement

Participants express disagreement regarding the implications of oxygen as a biomarker. While some acknowledge the potential for abiotic oxygen production, others maintain that it remains a strong indicator of biological processes. The discussion does not reach a consensus on the significance of these findings.

Contextual Notes

Limitations include the ongoing uncertainty about the mechanisms of abiotic oxygen production and the conditions under which oxygen may be present in planetary atmospheres. The discussion reflects a range of assumptions about the relationship between oxygen and life.

PF_SpaceNews
Oxygen is not definitive evidence of life on habitable extrasolar planets

The Earth's atmosphere contains oxygen because plants continuously produce it through photosynthesis. This abundant supply of oxygen allows life forms like animals to flourish. Therefore, oxygen had been thought to be an essential biomarker for life on extrasolar planets. But now, a research assistant professor Norio Narita of the Astrobiology Center of National Institutes of Natural Sciences (NINS), which was founded in April 2015, and an associate professor Shigeyuki Masaoka, of the Institute of Molecular Science of NINS, have presented a novel hypothesis that it could be possible for planets to have large quantities of abiotic (non-biologically produced) oxygen. This study is a good example of interdisciplinary studies that combine knowledge from different fields of science to promote astrobiology in the search for life on extrasolar planets. The study is published in Scientific Reports on Sep 10, 2015.

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Astronomy news on Phys.org
"Until now, it had been thought that if a planet has oxygen, that must mean that some form of plants are producing it through photosynthesis. Therefore, it had been assumed that when searching for signs of life on habitable extrasolar planets, the presence of oxygen in the atmosphere could be considered a definitive biomarker."

Read more at: http://phys.org/news/2015-09-oxygen-definitive-evidence-life-habitable.html#jCp

Bit of an overstatement to reach an obvious conclusion that "necessary" is not the same as "sufficient."
 
Bystander said:
Bit of an overstatement to reach an obvious conclusion that "necessary" is not the same as "sufficient."
Where do you see that?

Before: "We don't know abiotic sources of molecular oxygen, if we find oxygen in an atmosphere it should come from life"
Now: "We know an abiotic source of molecular oxygen, if we find oxygen in an atmosphere we don't know where it comes from"
 
mfb said:
Before: "We don't know abiotic sources of molecular oxygen
https://www.google.com/?gws_rd=ssl#q="iron+oxides"+"mantle+rocks"
See Lev Epplebaum (5th or 6th item in list) for clear statement of T, P stability of FeII over FeIII in mantle rock. Bottom line? Plenty of well-known sources of free oxygen in large quantities for atmospheres on rocky planets.
 
OK so a planet with a substantial surface layer of Titanium Oxide orbiting a star with strong UV emission might have an atmosphere with a lot of free oxygen.
That doesn't make it less plausible that free oxygen is a strong marker of photosynthetic life.
In fact I think that Titanium Oxide coated planets would be considerably more rare than planets having surface water and an abundance of Carbon/Nitrogen/Oxygen compounds, the prerequisites for organic chemistry.
 

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