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Oxygen Surprise in Earth’s Ancient Atmosphere

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An analysis of fossilised space dust collected form the Pilbara has challenged the accepted view that the Earth’s atmosphere was oxygen-poor 2.7 billion years ago.

The study, published in Nature (http://tinyurl.com/hk6msxw), found that the ancient Earth’s upper atmosphere contained about the same amount of oxygen as today, and that a layer of methane haze separated this oxygen-rich upper layer from the oxygen-starved lower atmosphere.

The international team extracted micrometeorites from samples of ancient limestone collected in the Pilbara region in Western Australia, and examined them at the Monash Centre for Electron Microscopy and the Australian Synchrotron.

“We found that most of the micrometeorites had once been particles of metallic iron – common in meteorites – that had been turned into iron oxide minerals in the upper atmosphere, indicating higher concentrations of oxygen than expected,” said Dr Andrew Tomkins of Monash University. “This was an exciting result because it is the first time anyone has found a way to sample the chemistry of the ancient Earth’s upper atmosphere,” he said.

Imperial College researcher Dr Matthew Genge calculated that oxygen concentrations in the upper atmosphere would need to be close to modern-day levels to explain the observations...

The full text of this article can be purchased from Informit.