Discovery challenges timeline of oxygen on Earth

Analysis of selected bands of the late Archean Mt. McRae Shale found in the upper 200 meters of the ABDP-9 core provide evidence of oxygen in Earth's atmosphere 50-100 million years earlier than previously known. The project, financially supported by NASA and NSF, brought researchers together from five universities, including Arizona State University, where the core samples used for research are housed. Also pictured is a vial of processed -- pummeled -- rock powder used for geochemical analysis. Credit: Arizona State University photo by Tim Trumble