Chinese Scientists Discover First Evidence of Impact-Formed Hematite in Chang'e-6 Lunar Samples
- MM24 News Desk
- 7 days ago
- 3 min read
A joint team from the Chinese Academy of Sciences and Shandong University has identified crystalline hematite and maghemite in moon samples from the Chang'e-6 mission, providing the first direct mineralogical evidence of a highly oxidized environment created by a massive impact on the lunar surface.
This discovery, published in Science Advances, challenges the long-standing view of the Moon as a purely reduced body and offers new clues to explain its mysterious magnetic anomalies.
The Moon has traditionally been considered a chemically "reduced" body, with iron existing in low-oxidation states. Finding highly oxidized iron minerals like hematite (α-Fe2O3) and maghemite (γ-Fe2O3) was thought to be unlikely. However, in a breakthrough study published on November 14 in Science Advances, researchers analyzing soil from the South Pole–Aitken (SPA) Basin have done just that.
The discovery was made by a collaborative team from the Institute of Geochemistry of the Chinese Academy of Sciences (IGCAS) and Shandong University. They examined the precious samples returned by China's Chang'e-6 mission, which successfully retrieved material from the SPA Basin—one of the largest and oldest impact craters in our solar system. This location, shaped by an extremely violent collision, provided the perfect setting to investigate whether giant impacts could create unique chemical environments.
"For a long time, the prevailing view was that the lunar surface was too reducing to form minerals like hematite," explained a researcher involved in the study. "Our findings show that major impacts can completely alter local conditions, creating a transient but powerful oxidizing environment."
The team identified micron-sized grains of hematite and confirmed their structure using a powerful suite of techniques, including micro-area electron microscopy and Raman spectroscopy. A critical part of their work was proving these grains were native to the Moon and not contaminants from Earth.
So, how did these oxidized minerals form in such an oxygen-poor global environment? The study proposes a compelling scenario directly tied to a massive impact event. The immense energy from such a collision would have vaporized surface materials, creating a temporary, high-temperature vapor cloud with a high oxygen fugacity. Within this cloud, a key reaction occurred: the desulfurization of the iron-sulfide mineral troilite.
This process released iron ions, which were then oxidized and deposited from the vapor phase to form the crystalline hematite and maghemite found in the samples.
This discovery has significant implications for solving one of the Moon's lingering puzzles: the origin of its widespread magnetic anomalies.
These magnetic patches have been difficult to explain, as the Moon lacks a global magnetic field. The formation of magnetic minerals like maghemite and magnetite through impact-driven oxidation provides a direct and plausible mechanism for creating these localized magnetic sources.
The findings build on earlier work on Chang'e-5 samples, which first hinted at impact-generated oxidized iron. However, the identification of well-crystalline hematite in the Chang'e-6 samples is a much more definitive piece of evidence, reported Science Advances. It confirms that large impacts are not just destructive forces but also powerful, localized chemical engines that can fundamentally alter the composition of a planetary surface.
This research, led by Chinese Academy of Sciences scientists, fundamentally rewrites a chapter of lunar geology. It demonstrates that the Moon's chemical history is more dynamic and complex than previously believed, influenced by catastrophic events that can temporarily create conditions thought to be impossible on a global scale.
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