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By Stephen Luntz

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First Oxygen Dated
The first substantial oxygen appeared in the atmosphere 2.48–2.32 billion years ago, A/Prof Mark Barley of the University of WA has concluded in work published in Nature.

The timing of the Great Oxidation Event, in which enough oxygen entered the atmosphere to affect the planet’s chemistry, has been hotly contested. Ratios of molybdenum, rhenium and uranium in the Hamersley Range place it at 2.5 billion years ago according to one study (AS, Nov/Dec 2007, p.13). However, other estimates are as early as 2.7 billion years ago.

The presence of oxygen can be detected because “aerobic-respiring bacteria which oxidise pyrite released acid that dissolved rocks and soils on land, including chromium, that was then carried to the oceans by the flow of water,” Barley said. The presence of chromium in sedimentary rocks indicates the presence of these bacteria.

Barley claimed that older estimates are a result of alterations to the rocks. “The banded iron formations have good representation of the geochemistry in the earth’s early ocean, but also a lot of [formations] were later altered.”

Bodybuilding Supplement Saves Muscle
L-tyrosine, an amino acid popular with bodybuilders, improves muscle strength and mobility in mice with a wasting disease.

Prof Edna Hardeman of the University of NSW...

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