China's Chang'e-6 mission has unearthed a lunar mystery, revealing a hidden truth beneath the Moon's surface. The mission's findings, published in Science Advances, have challenged long-held beliefs about the Moon's lack of atmospheric activity and low oxygen levels. The discovery of hematite and maghemite, two highly oxidized minerals, in samples from the South Pole-Aitken (SPA) Basin, one of the Moon's oldest and largest impact craters, has scientists rethinking their understanding of lunar geology.
The minerals, found in samples collected from the SPA Basin, were confirmed to be crystalline hematite and maghemite using advanced techniques by a team from the Institute of Geochemistry at the Chinese Academy of Sciences and Shandong University. This discovery suggests that, under specific conditions, even the Moon can host highly oxidized minerals, despite its lack of atmosphere and low oxygen levels.
The SPA Basin, a massive scar on the Moon's far side, was created by a colossal impact billions of years ago. The researchers employed electron microscopy, electron energy loss spectroscopy, and Raman spectroscopy to study the samples, revealing that the minerals were native to the Moon and not brought from Earth. This marks the first time that hematite and maghemite, in their crystalline form, have been directly identified in lunar material returned to Earth.
The team's findings suggest that large asteroid impacts generated intense heat, vaporizing surface materials and creating a high-oxygen vapor cloud. This cloud triggered the oxidation of iron from lunar minerals like troilite, resulting in the formation of hematite and maghemite. These minerals were found alongside magnetite, indicating a range of oxidation states linked to the same process.
The study also highlights a potential connection between these oxidized iron minerals and long-standing magnetic anomalies observed on the Moon. Regions like the northwestern SPA Basin exhibit unexplained magnetic signatures, and the presence of hematite and maghemite as magnetic carriers may help explain these anomalies. The research team noted that the findings provide key sample-based evidence to clarify the carriers and evolutionary history of these lunar magnetic anomalies.
By linking oxidation processes with ancient impact events, the study offers a new perspective on the Moon's geological evolution. The direct observation of hematite in returned samples bridges the gap between remote sensing data and ground truth, adding a layer of complexity to our understanding of the Moon's past and present.
