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Nickel "Famine" Led to Oxygen-Breathing Life?

  • 13-04-2009 12:12pm
    Registered Users Posts: 30,747 ✭✭✭✭ Galvasean
    Life as we know it may have evolved because Earth's early oceans ran low on nickel, a new study suggests.

    The metal is an important nutrient for a class of bacteria known as methanogens, which produce methane, a gas that reacts easily with oxygen.

    Methanogens flourished on early Earth, presumably filling the atmosphere with methane gas, said study leader Kurt Konhauser, a geomicrobiologist at the University of Alberta.

    "The methanogenic bacteria were very happy until 2.5 billion years ago," he said.

    At that point, rocks from the era show that atmospheric oxygen started to rise, which would suggest that methane levels dropped. But the exact reason for the oxygen spike has been a long-standing puzzle.

    Konhauser's team looked for an answer in rocks found in Ontario, Canada, that formed on the ancient sea floor.

    "Studying them gives a history of seawater," he said.

    What they found is that older rocks had metal concentrations high in nickel, while the rocks that formed after them had less of the nutrient.

    The scientists suggest that cooling of the Earth's mantle decreased eruptions of nickel-rich volcanic rock, which meant that less nickel was being weathered from the rocks and dissolved in the oceans.

    This nickel "famine" starved the methanogens, spurring a gradual decline in atmospheric methane, the researchers think.

    Meanwhile, a class of photosynthetic bacteria known as cyanobacteria, which had been on the scene since 2.7 to 2.8 billion years ago, was continuing to produce oxygen.

    With less methane around to tie it up, oxygen accumulated in the atmosphere, eventually creating conditions for oxygen-breathing life to dominate.

    The finding, Konhauser added, would help explain why there was a 300- to 400-million-year delay between when cyanobacteria appeared and oxygen began building up in the atmosphere.

    Findings appear in this week's issue of the journal Nature.

    It's weird to think that there was once life without the need for oxygen.


  • Moderators, Science, Health & Environment Moderators Posts: 10,073 marco_polo

    Galvasean wrote: »

    It's weird to think that there was once life without the need for oxygen.

    It seems most likely that these hardy fellows have reevolved the capacity to survive without oxygen.

    Chemical analysis of effluent from the inaccessible subglacial pool suggests that its inhabitants have eked out a living by breathing iron leached from bedrock with the help of a sulfur catalyst. Lacking any light to support photosynthesis, the microbes have presumably survived by feeding on the organic matter trapped with them when the massive Taylor Glacier sealed off their habitat an estimated 1.5 to 2 million years ago

  • Moderators, Science, Health & Environment Moderators Posts: 10,073 marco_polo

    Or was the earth really so oxygen poor 2.4 billion years ago?

    Hardly positive evidence in favour of an earlier date for an oxygen rich atmosphere of the earth, but casts a little doubt on whether or not abnormal isotope fractionation (of sulfur) in rock can be definatively be linked to low levels of oxygen in the atmosphere.