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Earth's Hot Core May Have More Oxygen Than Once Thought

First Posted: Sep 23, 2015 08:47 AM EDT
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There may be more oxygen in Earth's core than once thought. Scientists have made some new findings about Earth's interior by considering the geophysical and geochemical signatures of the core and mantle together.

Earth formed about 4.56 billion years ago over a period of several tens of millions of years through the accretion of planetary embryos and planetesimals. The energy delivered by progressively larger impacts maintained Earth's outer layer and an extensively molten magma ocean. Gravitational separation of metal and silicate within the magma ocean results in the planet characterized by a metalliccore and a silicate mantle.

The formation of Earth's core left behind geophysical and geochemical signatures in the core and mantle that remain to this day. In the past, core formation models have only attempted to address the evolution of core and mantle compositional signature separately rather than looking for a joint solution.

The researchers examined data available and found that core formation occurred in a hot, moderately deep magma ocean exceeding 1,800-kilometer depth, under conditions that were more oxidized than present-day Earth.

"This new model is at odds with the current belief that core formation occurred under reduction conditions," said Rick Ryerson, one of the researchers, in a news release. "Instead we found that Earth's magma ocean started out oxidized and has become reduced through time by oxygen incorporation into the core."

In fact, based on the higher oxygen concentration of the core, the researchers believe that the Earth must have accreted material that is more oxidized than the present-day mantle, similar to that of planetesimals such as asteroidal bodies.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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