A team of Chinese scientists has just debunked a long-accepted idea: they have found iron oxide, specifically hematite and maghemite, in samples of lunar soil brought back by the Chang’e-6 mission. The discovery challenges our traditional conception of the Moon’s chemistry.
The analysis, published in Science Advances, is surprising because the Moon lacks a stable atmosphere and water, conditions that on Earth facilitate the formation of iron oxides. In an environment as “reducing” as the lunar one, with very little free oxygen, it was believed that these compounds could not form naturally.
How did those oxides get there? The authors of the study, scientists from Shandong University, the Institute of Geoscience of the Chinese Academy of Sciences and Yunnan University, used advanced techniques: electron microscopy, Raman spectroscopy and energy loss spectroscopy, among others, to confirm that these minerals are authentically lunar, not terrestrial contamination.
The most plausible hypothesis, they point out in a statement, is that billions of years ago, gigantic meteorite impacts created extreme conditions. In those clashes, Gases with high oxygen content were generated, enough to oxidize certain iron minerals present on the Moon (such as troilite, an iron sulfide).
This process, which occurs at very high temperatures (between 700 and 1,000 °Caccording to the study), would allow hematite to form by vapor phase deposition. Furthermore, one of the intermediate products of this process are other magnetic minerals, such as magnetite, which could help explain some magnetic anomalies observed in certain lunar areas, especially in the Aitken basin region, precisely where Chang’e-6 collected part of its samples.
What does this finding mean? First, that contradicts an ancient view: that the Moon is a chemically “dead” worldwithout active oxidation processes. Instead, there could be mechanisms (albeit rare) that cause oxidation of the lunar regolith.
This type of impact-driven oxidation It gives us clues about what collisions were like on the early Moon, how the gases released in those collisions behaved, and how it evolved. its surface over time.
With this knowledge, future missions could analyze similar areas to see if there are more oxides, which would help map the distribution of these minerals and better understand the evolution of the satellite. This would allow answering questions related to the presence of hematite and maghemite in other lunar regions and know if it is a common or extraordinary phenomenon.