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Research suggests magma of the early Earth was highly oxidizing

Highly oxidizing magma of the early Earth
The bright area at the center of the image shows quenched metallic melt and the surrounding grey area indicates quenched silicate melt. The sample was encapsulated into a graphite capsule, which is transformed into diamond during heating experiments. Credit: Geodynamics Research Center, Ehime University

Understanding the atmosphere and surface environment of the early Earth, especially before the origin of life, is a key to understanding the habitability of the Earth.

The atmosphere of terrestrial planets has been thought to be formed by degassing volatiles from the interior and its composition is mainly controlled by the of the . To understand the mantle oxidation state, the abundance of ferrous (Fe2+) and ferric (Fe3+) iron in the mantle are key because the mantle oxidation state varies with the relative abundance of these two .

Ehime University has led an experimental study showing that the formation efficiency of Fe3+ via redox disproportionation of Fe2+ in metal-saturated magma under high pressures corresponding to the depth of the lower mantle is higher than previously thought. The findings are published in the journal Nature Geoscience.

In this reaction, Fe3+ and metallic iron (Fe0) are formed from 2Fe2+, and the segregation of Fe0 into the core increases the content of Fe3+ in the residual magma and its oxidation state. The experimental results indicate that the Fe3+ content of the Earth's magma ocean during core formation was about one order of magnitude higher than the present upper mantle.

This suggests that the magma ocean was much more oxidizing than the present Earth's mantle after the , and the atmosphere formed by the degassing of volatiles from such a highly oxidizing magma would have been rich in CO2 and SO2. In addition, the authors found that the estimated oxidation state of the Earth's can explain that of Hadean magmas of more than 4 billion years ago by inference from geological records.

Because the formation efficiency of biomolecules in a CO2-rich is quite low, the authors speculated that the late accretion of reducing materials after the formation of the Earth played an important role in supplying biologically available organic molecules and the formation of a habitable environment.

More information: Hideharu Kuwahara et al, Hadean mantle oxidation inferred from melting of peridotite under lower-mantle conditions, Nature Geoscience (2023). DOI: 10.1038/s41561-023-01169-4

Journal information: Nature Geoscience

Provided by Ehime University

Citation: Research suggests magma of the early Earth was highly oxidizing (2023, July 6) retrieved 17 June 2024 from
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