Earth’s oxygen is different from that found on the Moon

Hyperaxion Mar 11, 2020

According to experts, the discovery challenges the current theory about the formation of our natural satellite.

A new article published in the journal Nature Geoscience suggests that the composition of oxygen present on Earth is different from that found on the Moon, which may challenge our current understanding of how the satellite formed. To carry out the discovery, the researchers responsible for the study evaluated the isotopes of the substance present in lunar samples and compared them with terrestrial ones.

The most common theory of the formation of the Moon is the Giant Impact Hypothesis, which suggests that our satellite was formed from debris resulting from the collision between the primitive Earth and a protoplanet called Theia. That’s why, according to scientists, our planet and the Moon are geochemically similar – and the lunar samples collected during the Apollo missions, in fact, are almost identical in composition to the oxygen isotopes here.

The Giant Impact Hypothesis suggests that our satellite was formed from debris resulting from the collision between the primitive Earth and a protoplanet called Theia.
(Credit: ExtremeTech).

However, although the hypothesis explains the geochemical similarities between the Earth and the Moon, it remains unclear how it happened. For the experts, there are two alternatives: either the two bodies that collided had identical composition (which is very unlikely), or their oxygen isotopes were completely mixed after the impact.

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In the new study, the team evaluated oxygen isotopes present in several types of lunar rocks of different depths within its mantle. So, after the analyzes, the researchers found that the composition of the substance varied according to the part of the Moon from which it came.

“Our findings suggest that the deep lunar mantle may have experienced less mixing and is more representative of Theia’s impact,” said Erick Cano, one of the researchers, in a statement. “The data suggests that the distinctive oxygen isotope compositions of Theia and the Earth have not been completely homogenized by the impact that formed the Moon and provide quantitative evidence that Theia could have formed farther from the Sun than our planet.”

According to the researchers, the article is important because it eliminates the need for giant impact models that include a complete homogenization of oxygen isotopes between the Earth and the Moon. “Based on the results from our isotopic analysis, Theia would have an origin farther out from the Sun relative to Earth and shows that Theia’s distinct oxygen isotope composition was not completely lost through homogenization during the giant impact,” noted Zach Sharp, co-author of the study.

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