Researchers from NAI's Carnegie Institution of Washington Team have a paper in Nature describing evidence that Earth's Mesoarchean atmosphere (3.2 and 2.8 Gya) possessed very low amounts oxygen. These findings contrast with prior claims that Earth's atmosphere underwent its first rise in oxygen during the Mesoarchean, and indicate that oxygen first rose above parts per million levels sometime between 2.45 and 2.4 billion years ago. [Source: NAI Newsletter]