> planets are big, atmospheres are big, and life is small; And time is long. The consensus is still that the oxygenation of Earth's atmosphere took "at least

> planets are big, atmospheres are big, and life is small; And time is long. The consensus is still that the oxygenation of Earth's atmosphere took "at least 400 million years". A lot of that is due to the "great rust", i.e. minerals that would take oxygen out of the air had to first exhaust their capacity to oxidise. This took "nearly a billion years". Iron ore deposits are from the seabed of this period. See: https://en.wikipedia.org/wiki/Great_Oxidation_Event https://en.wikipedia.org/wiki/Great_Oxidation_Event https://en.wikipedia.org/wiki/Banded_iron_formation https://en.wikipedia.org/wiki/Banded_iron_formation