Rexamining the "whiff of oxygen" (IMAGE) Dartmouth College Caption Electron microscopy revealed that the Mount McRae Shale is made of volcanic glass shards (light grey, left), which could be a source of the molybdenum concentrated in the “whiff” interval during later fluid flow events that have previously been taken to indicate early atmospheric oxygen. These events are recorded in the iron-sulfur mineral pyrite within the dark grey shale of the “whiff” interval; here a scanned image (right) shows both early-formed round nodules with diffuse halos and parallel lines of tiny crystals that formed during later fluid flow. Credit From Science Advances, Slotznick et al., “Re-examination of 2.5 Ga ‘Whiff’ of Oxygen Interval Points to Anoxic Ocean Before GOE,” January 5, 2022. This work is licensed under CC BY-NC (http://creativecommons.org/licenses/by-nc/4.0/). Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. License CC BY-NC Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.