The Early Earth

The oceans of the Archean (3.8-2.5 billion years ago) and Proterozoic (2.5-0.8 billion years ago) eons had the water composition that was very different than today. They contained very little sulfate, their deep waters contained dissolved ferrous (+2) iron, and oxygen levels were several orders of magnitude lower than at present. Life in this nearly anoxic world consisted of microbes, which survived on metabolisms that today are found only in rather special environments. We use some special rare lakes that have these unique water chemistries to understand the ways life existed at those early stages of our planet. These are lakes Matano in Indonesia, Lake Kivu in Rwanda, and two recently discovered lakes in the US Midwest. We also perform numerical modeling of microbial geochemistry to understand how those early microbes fractionated sulfur isotopes, to compare the results with the rock record and infer their metabolic parameters.