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Oxygen is not definitive evidence of life on habitable extrasolar planets

  1. Sep 15, 2015 #1
    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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  3. Sep 15, 2015 #2

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    "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."
     
  4. Sep 16, 2015 #3

    mfb

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    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"
     
  5. Sep 16, 2015 #4

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    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.
     
  6. Sep 16, 2015 #5
    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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