Researchers simulate processes prevailing in early magma oceans

phys.org | 11/27/2017 | Staff
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The reason why the Earth's atmosphere has contained so much oxygen since about two billion years ago compared to the atmospheres of other known planets has for a long time remained a mystery. Researchers at the Bavarian Research Institute of Experimental Geochemistry & Geophysics (BGI) at the University of Bayreuth recently used high-pressure experiments to substantiate a hitherto unproven suspicion: In early geological history, high pressure in magma oceans triggered processes that resulted in the Earth's upper mantle becoming highly oxidized. This subsequently led to oxygen-rich compounds such as carbon dioxide and water vapor escaping from the mantle into the atmosphere. The scientists have presented their findings in the journal Science.

It has been known for some time that during the formation of the Earth many smaller celestial bodies—so-called planetary embryos and planetoids—impacted on its surface. Enormous amounts of energy were released in the process, melting large quantities of rock. Hot magma oceans were formed in the Earth's mantle, extending to a depth of up to 2,500 kilometers and containing oxidized iron Fe2+ ("ferrous iron"). The Bayreuth scientists simulated the pressures that acted on Fe2+ in magma oceans in a series of high-pressure experiments. For this purpose, pressures of more than 20 gigapascals were generated in BGI's laboratories. "That's the equivalent of putting the entire mass of the Eiffel Tower on an object the size of a golf ball," says Katherine Armstrong, lead author of the study, who received her doctorate from the University of Bayreuth and now works at the University of California Davis.

Runs - Fe2+-containing - Rock

In numerous experimental runs, Fe2+-containing rock was exposed to extremely...
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