Ariel is a coauthor on four papers in the journal Science that have emerged out of study of sediments in Western Australia deposited during the Late Archean, 2.5 billion years ago These papers all provide evidence of trace amounts of O2 in the environment before the transition to a generally oxidizing atmosphere. The latest paper is in the October 30th issue. You can read about some of the results here. This latest work is in conjunction with collaborator Tim Lyons at University of California, Riverside and is first-authored by UCR grad student Chris Reinhard. The paper studies iron speciation in black shales, and demonstrates that the early oxygenation of the Earth system was more nuanced and variable than previously thought.