Of Ancient Iron and Oxygen

摘要

Finding clues to understand the early evolution of ocean and atmospheric chemistry and its links to the evolution of life remains a daunting task. Often just a few rock samples provide our only evidence of what conditions on Earth were like long ago. Reinhard et al. (p. 713) combined iron speciation data from a 2.5-billion-year-old shale from Australia with sulfur isotope data from this and nearby formations to conclude that oxygen chemistry predominanty consisted of an anoxic sulfide-rich water column, instead of iron-rich oceans, as previously speculated.