What best evidences there are that demonstrate what Earth was like in its early years? According to this video Earth started out with no oxygen in its atmosphere. And according to this link the Earth's atmosphere was dominated by carbon dioxide similar to Venus. But is there any evidence to support this?

EDIT: Just adding some links that claim to know or believe how Earth's atmosphere has evolved.

http://scijinks.jpl.nasa.gov/atmosphere-formation

http://www.ux1.eiu.edu/~cfjps/1400/atmos_origin.html

http://www.chem.duke.edu/~jds/cruise_chem/Exobiology/PBearth.html

  • I am far from being an expert on the topic, but I guess this could be a good starting paper to read: Earth's early atmosphere. - Kasting, Science 1993 – nico Sep 30 '12 at 14:33
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    Pedantic aside: "Earth started out with no oxygen" is simply wrong. The phrase you are looking for is something like "no free oxygen in the atmosphere": there was oxygen all over the place, it was just bound up in compounds. – dmckee Sep 30 '12 at 16:49

Dr. G. Arnold is one of the world's leading authorities in molybdenum redox, which is a cornerstone of the anoxic (oxygen deficient) early-atmosphere model.

You can read many paper by her-and-team that reinforce the anoxic atmosphere hypothesis.

A simple way to think of the evidence: Molybdenum is very sensitive to redox, an chemical process that involves oxygen. These charts on p1904 show that no redox occurred below a certain depth that is correlated with time... i.e. when that rock was exposed to the earth's surface or ocean floor. Since no redox occurred below a certain level, no oxygen was in the atmosphere.

Whether or not anoxic atmospheres are pre/non-biotic...... that is a whole separate discussion. (and why Science is so hard for many to care about, I think. People want simple narrative packages, without many loose ends)

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    Could you expand a little bit more, citing relevant parts of the papers and summarizing results/conclusions? – nico Sep 30 '12 at 19:31
  • @nico I have tried. The papers all deal with critically-important parts of the Mo redox cycle in the early earth – so they are all quite relevant. The question is inherently one that requires a grasp of geochemistry. I think if you can't read these papers, then you might as well take the word of whatever source you trust to interpret science for you. Skeptics are Researchers, yes? – New Alexandria Sep 30 '12 at 19:42
  • @NewAkexandria: well, yes and no. Surely I will tend to trust a peer-reviewed study more than a random blog post. However, I am a researcher but cannot completely judge how good those papers are. I guess if I gave you papers about neuroendocrinology (which I can judge pretty well), you might be in a similar situation: you would understand the general message, but possibly you would not be able to get certain subtle points the paper fails to make. I think the answer is OK, as it gives good sources but could be expanded even more. The fact that there are experts here does not mean everyone is. – nico Sep 30 '12 at 19:57
  • @nico I would just look at the impact factor of the journals that pub'd the articles you cited. As people that know to evaluate journals, we should share this kind of info. – New Alexandria Sep 30 '12 at 20:48
  • IF is surely a good indication (and Science is a good journal, nothing to say there), but it is far from perfect. The equation high IF = high quality / low IF = low quality is often not true. Anyway, my point is: it would be nice to have an answer that is self-sufficient and this is not (i.e.: you have to read those papers to understand the answer). The answer should stand by itself, and the references should be there to support what you write (just my 2¢ on how to improve this answer, nothing personal of course) – nico Sep 30 '12 at 21:18

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