Ironing Out Biosphere Oxidation

Various lines of evidence now indicate that the atmosphere became oxygen-rich about 2.3 billion years ago. In his perspective, [Kump][1] describes work by [Rouxel and colleagues][2] who used the stable isotopic composition of iron minerals to explore the environmental context of this monumental global change. [1]: http://www.sciencemag.org/cgi/content/full/307/5712/1058 [2]: http://www.sciencemag.org/cgi/content/short/307/5712/1088