>Thanks for posting this art. I had thought that the last nail had been
>driven into the reducing atomosphere's coffin years ago. In any event,
>I wanted to make sure I understood the notation Ga. I presume
>the authors are saying the Earths atmosphere may have been
>oxidizing as long as 3.0 billion years ago?
Yes, that's correct.
>
>My understanding is that present wisdom indicates that
>the Earth's atmosphere never was reducing, even at the
>time of the origin of life (somewhere between 3.5 and 4.0
>billion years ago). IMHO, this is a major nail in the coffin
>of classical soup theory since Miller-Urey experiments
>have at least 2 orders of magnitude smaller yields of amino
>acids in neutral and mildly reducing atmospheres.
And this is not neutral or mildly reducing. The author emphasizes
repeatedly that his percentage is a minimum, and likely there was more O2
than that.
Art
http://chadwicka.swau.edu