The most certain thing we know about early Earth is that we don’t know much about it. From ScienceDaily:
For at least a billion years of the distant past, planet Earth should have been frozen over but wasn’t. Scientists thought they knew why, but a new modeling study has fired the lead actor in that long-accepted scenario.
It’s been assumed that Earth depended on methane to stay warm for billions of years. Oxygen was building up and was thought to destroy the methane. The new study argues that sulfate was a much bigger menace to methane.
Sulfate wasn’t a factor until oxygen appeared in the atmosphere and triggered oxidative weathering of rocks on land. The breakdown of minerals such as pyrite produces sulfate, which then flows down rivers to the oceans. Less oxygen means less sulfate, but even 1 percent of the modern abundance is sufficient to kill methane, Olson said.
Olson and her Alternative Earths coauthors, Chris Reinhard, an assistant professor of earth and atmospheric sciences at Georgia Tech University, and Timothy Lyons, a distinguished professor of biogeochemistry at UC Riverside, assert that during the billion years they assessed, sulfate in the ocean limited atmospheric methane to only 1 to 10 parts per million — a tiny fraction of the copious 300 parts per million touted by some previous models.
The fatal flaw of those past climate models and their predictions for atmospheric composition, Olson said, is that they ignore what happens in the oceans, where most methane originates as specialized bacteria decompose organic matter.
Paper. (paywall) – Stephanie L. Olson, Christopher T. Reinhard, Timothy W. Lyons. Limited role for methane in the mid-Proterozoic greenhouse. Proceedings of the National Academy of Sciences, 2016; 201608549 DOI: 10.1073/pnas.1608549113 More.
The wonderful thing about these controversies is that they go on and on and no one loses their job. That’s what happens when one deals with actual history, as opposed to, say, an ideology like Darwinism.
See also: What we know and don’t know about the origin of life
and
What the fossils told us in their own words
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