August 25, 2006 | David F. Coppedge

Early Oxygen Fuels Fire in OOL Camp

Live Science reported a new claim about oxygen on the early earth appearing far earlier than usually assumed.  A Penn State astrobiologist is claiming that uniformly high oxygen levels existed on earth 3.8 billion years ago, a billion years before previous estimates.
    Oxygen’s presence on Earth has been typically inferred from sulfur isotope levels in rocks due to the way ultraviolet light processes volcanic gases in the absence of ozone.  Hirosho Ohmoto, director of Penn State’s Astrobiology Research Center, found modern-like sulfur isotope signatures in Australian rocks dated at nearly 3 billion years old.  His team’s findings, publishing in Nature this week,2 suggest not only that oxygen was present far earlier, but casts doubt on the detection technique used to infer its presence: the sulfur isotope signature “was mostly created by non-photochemical reactions during sediment diagenesis, and thus is not linked to atmospheric chemistry.”
    This announcement is producing emotional as well as chemical reactions.  The LiveScience article states,

“There is going to be a howl, even outrage,” over these findings, geologist and isotope geochemist Paul Knauth at Arizona State University told LiveScience.  They will say hot springs could have swamped the rocks Ohmoto and his colleagues looked at with normal sulfur, or that the crystals they analyzed washed in from elsewhere, or that their measurements are inaccurate, he said.  However, Knauth noted Ohmoto and his colleagues did address these points “and make good arguments.”

The problem with oxygen is that it is highly reactive and destructive to prebiotic chemicals.  None of the amino acids or other “building blocks of life” famous from the Miller experiment and similar tests would have formed in the presence of oxygen.  Astrobiologists had assumed that no oxygen was present until the emergence of photosynthetic bacteria, some two billion years after the formation of the earth.
    This finding has implications for other planets, too.  Ohmoto believes that early oxygen could be a common characteristic on planets around other stars.  His paper did not address the impact this finding would have on research into the origin of life [OOL].  He only told LiveScience that the question of when oxygen first appeared on the early earth “is closely linked to those related to the biological evolution on Earth and other planets,” an ambiguous and indirect comment at best.  Reporter Charles Q. Choi seemed to think this was good news.  He titled his article, “Alien life might arise quickly, study suggests,” and began,

Scientists have found that oxygen and the life that generates it might have enriched the Earth far earlier than currently supposed.
    The discovery, sure to be controversial, suggests life could arise earlier than now thought on alien planets, too.


1Ohmoto et al., “Sulphur isotope evidence for an oxic Archaean atmosphere,” Nature 442, 908-911(24 August 2006) | doi:10.1038/nature05044; Received 21 June 2005; Accepted 10 July 2006.

For spinning a disastrous finding into a blessing, Choi wins Stupid Evolution Quote of the Week.  Bringing oxygen into the picture before photosynthesis is like bringing out the rugby team before the grass has sprouted.  The astrobiology gardeners will only get mud if Ohmoto is correct.  Early oxygen will destroy any chances of life starting by chemical evolution (as if that fairy tale had a chance to begin with).  If they respond like Choi and just assume this implies “alien life might arise quickly,” then they must believe a second miracle, that the complexities of photosynthesis also arose quickly.  Watch those miracle words emerged, appeared, and arose.  Words can’t short-circuit reality.  Arose by any other name would smell as cheat.

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Categories: Origin of Life

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