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3.2 billion year old oxygen found on Earth

  1. Oct 7, 2015 #1

    wolram

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    http://www.sciencedaily.com/releases/2015/10/151006192107.htm

    A new study shows that iron-bearing rocks that formed at the ocean floor 3.2 billion years ago carry unmistakable evidence of oxygen. The only logical source for that oxygen is the earliest known example of photosynthesis by living organisms, say geoscientists.
     
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  3. Oct 7, 2015 #2

    wolram

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  4. Oct 22, 2015 #3
    I'd take that with a grain of salt. The earth was pretty hostile back then, and photosynthesis only can happen in the top few meters of water. That exposes them to radiation in the early earth and if they were in shallow water, the moon being so much closer back then caused tides from hell.

    There is another logical source of oxygen: electrolysis. The early earth was covered in clouds and probably had constant rains. It also would have had copious amounts of lightning tearing H2O apart.

    That said, I'm certain there was life on earth at the time and it probably did come from life. The first oxygen produced also certainly ended up on the ocean floor, the early ocean was full of iron and any free oxygen would have bonded to it easily. There would have to be a significant delay between the first O2 producing life and the buildup in the atmosphere, the ocean back then would have been a giant O2 sink.

    Photosynthesis is what I have a hard time with, are there any other biological functions that produce molecular oxygen?
     
  5. Oct 25, 2015 #4

    Chronos

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    A crude form of molecular photosynthesis was probably a factor 3.5 billion years ago.
     
  6. Oct 28, 2015 #5
    Hostile to macro-organic lifeforms that constitute our day-to-day environment, yes. Hostile for micro-organisms that had emerged in and evolved in that environment? Surely not so much.

    What is your evidence for this claim? 3.5 billion years ago is not the early Earth. The Earth had 1.0 billion years since its formation to "settle down". And any oxygen generated in the atmosphere would more likely combine with volcanic gases than be absorbed in the ocean.
     
  7. Oct 28, 2015 #6
    Are you claiming there were few clouds? I don't know either way, but we get plenty of lightning now, including the occasional dry lightning balls.

    If you walk down a beach after a storm, there's a good chance you'll find sand fused into rocks by lightning. And that's just on one afternoon. Given a million years, this seems like a fair source of trace oxygen. At least good enough not to be dismissed out of hand.

    I would think one of the steps in moving from speculation to solid, testable hypothesis would be to definitively rule out conundrums such as this lightning thing. It's not enough to assume lightning didn't exist without showing it somehow.

    Would the atmosphere have absorbed all the gas? Even the gas created under the water's surface? (Lightning behaves strangely when it reaches the water. It seems to continue for some distance depending on the resistivity of the water.)

    Perhaps an experiment or three is in order?
     
  8. Oct 31, 2015 #7
    newjerseyrunner stated that "the early Earth was covered with in clouds and probably had constant rains".
    1. It would not be standard usage to refer to the Earth 3 billion years ago as "the early Earth".
    2. It is true that the early Earth, say between 4 and 4.5 billion years ago was often covered with clouds and at times had incessant rain.
    3. I know of no evidence that the Earth 3 billion years ago was covered with clouds, or had constant rains. (Indeed there is probably good evidence that such was not the case.)
    4. If you simply wish to argue that the frequency and magnitude of lightning strikes then was comparable with what we experience today, then I agree this is quite plausible. It was the other member's claim of an early Earth, covered with clouds and experiencing constant rains that I objected to.

    The major sink for any oxygen that might be generated in this way would not be the ocean, as you suggest, but combination with volcanic gases. Volcanic activity was within an order of magnitude of what we see today and so there is little chance for the build up you suggest occurring over a million years.

    I agree with you that other sources of oxygen need to be considered.
     
  9. Nov 1, 2015 #8
    Using round figures,
    Mass of atmosphere = 5 x 1018 kg
    Mass of oxygen in atmosphere = 1 x 1018 kg ( 1 x 1015 tonnes )

    If all the atmospheric oxygen came from water at 1000kg/m3 ( water mostly oxygen )
    Thus, Volume of water = 1 x 1015 m3 ( times 2 for O2 )
    Or 1 x 1015 tonnes of water

    Or a cube of water 1 x 105 m per side.
    Or a cube of water 100 km per side.

    A few mountains of water, something like the size of Everest, would have to dissassociate into as oxygen to make and keep the atmosphere the way as we know it.

    Iron oxide mountains - there would have to a few more mountains.

    One would need that many bugs working away to make an atmosphere richer in oxygen, if that is the method and means, and where "that many bugs" would be a figure to be determined somehow.

    Present biomass in terms of carbon. ( all organisms , not just photsynthetic )
    1 x 1012 tonnes of carbon ( rough figure ) ( amount of bacteria unknown, but by some estimates more than that of all other biomass )

    https://en.wikipedia.org/wiki/Biomass_(ecology [Broken])

    In the early earth, that 20% figure would have to be 100%.

    We could use a ratio of carbon biomass/ atmospheric oxygen as a guide, and assume bacterial biomass is the total biomass.
    In which case 1012 / 1015 which gives each carbon unit is responsible for 1000 units of atmospheric oxygen.

    Actual corelation ?? in the early earth.
    Bacterial output of oxygen would have to be > reconversion back to locked in oxgen as a compound.

    That would be a lot of bacteria, even if the atmospheric oxygen was 1%.

    Very crude, and open to criticism.
     
    Last edited by a moderator: May 7, 2017
  10. Nov 4, 2015 #9
    An international team said that they detected “a lot” of molecular oxygen in the cloud of gas, or coma, surrounding the nucleus of comet 67P/Churyumov–Gerasimenko. The findings were reported in the journal Nature on 29 October 2015.
     
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