Using high-resolution electron microscope imaging and spectroscopy, the researchers were able to conduct a set of complex analyses of the Suizhou meteorite sample in nanometer scale.

Through these analyses, the research team discovered metallic iron nanoparticles coexisting with bridgmanite in the shocked meteorite sample, representing the first direct evidence in nature of the iron disproportionation reaction, which so far had only been observed in high-pressure experiments.

“This discovery demonstrates that charge disproportionation can occur in natural high-pressure environments and therefore in the deep interior of the Earth,” Shim said.

The implications of this study, however, go beyond just this discovery and may ultimately help us understand the greater question of how Earth itself was oxidized. 

Although we know that Earth’s upper mantle is more oxidizing than other planets and that the more oxidizing conditions of the upper mantle may be linked to the sudden rise of oxygen in the atmosphere 2.5 billion years ago, we don’t yet know how the upper mantle of the Earth became more oxidizing.

“It is possible that when materials of the lower mantle are transported to the upper mantle by convection, there would be a loss of metallic iron and the oxidized iron in bridgmanite would cause more oxidizing conditions in the upper mantle,” Shim said. 

“Our discovery provides a possible explanation for the more oxidizing conditions of the Earth’s upper mantle and supports the idea that deep interior processes may have contributed to the great oxygenation event on the surface.”

Karin Valentine

Media Relations & Marketing manager, School of Earth and Space Exploration

480-965-9345