Discovery Challenges Timeline of Oxygen on Earth

From PhysOrg.com - latest science and technology news:

Two multinational teams of scientists, including four researchers from Arizona State University, are reporting that traces of oxygen appeared in Earth`s atmosphere 50 to 100 million years before the Â"Great Oxidation Event.Â" This event happened between 2.3 and 2.4 billion years ago when most geoscientists think atmospheric oxygen rose sharply from very low levels. The amount of oxygen before that time is uncertain and controversial. Analyzing layers of sedimentary rock in a kilometer-long core sample from the Hamersley Basin in Western Australia, the researchers report finding evidence that a small but significant amount of oxygen - a whiff - was present in the oceans and possibly Earth's atmosphere 2.5 billion years ago. The data also suggest that oxygen was nearly undetectable just before that time. Their findings appear in a pair of papers in the Sept. 28 issue of the scientific journal Science.

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