Oxygen pollution began earlier than we ever thought

Climate change for the anaerobes

Earth's atmosphere had oxygen in it 50-100m years earlier than anyone ever thought, according to new research from NASA.

The scientists were studying kilometre long core samples from Western Australia, in a bid to understand conditions on our planet before the rise of oxygen in the atmosphere, known as the Great Oxidation Event.

The core sample contains a continuous record of the conditions on earth, almost as if someone had left a giant tape recorder running, keeping a tidy record of the state of the planet throughout the ages.

By analysing the abundance of various metals and sulphur isotopes, the team was able to confirm that the corrosive gas was floating around the atmosphere at times predating the GOE, something no one was expecting.

"We seem to have captured a piece of time during which the amount of oxygen was actually changing - caught in the act, as it were," said Ariel Anbar, an associate professor at Arizona State University, Tempe, and leader of one of the research teams.

Anbar and his team were tracking amounts of trace metals whose quantity in oceans and sediments is governed by the amount of oxygen in the atmosphere. The other research team, led by Alan Kaufman of the University of Maryland, analysed sulphur isotopes, also a function of the abundance of oxygen.

The notion that organisms started to produce oxygen a little earlier is not totally new. Some scientists support the idea that oxygen production began on a small scale, and that the quantities produced were quickly absorbed by volcanic gases and rocks.

"What we have now is new evidence for some oxygen in the environment 50 to 100 million years before the big rise of oxygen," Anbar said. "Our findings strengthen the notion that organisms learned to produce oxygen long before the Great Oxidation Event, and that the rise of oxygen in the atmosphere ultimately was controlled by geological processes." ®

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