A fascinating new study from researchers at the Institute of Geochemistry, Chinese Academy of Sciences (IGCAS) and Shandong University has revealed the first concrete evidence of oxidized iron forms—specifically hematite (α-Fe₂O₃) and maghemite (γ-Fe₂O₃)—in lunar soil collected by China’s Chang’e-6 mission. This discovery was made at the vast South Pole-Aitken (SPA) Basin, one of the Moon’s oldest craters. The research, published on November 14 in Science Advances, marks a significant milestone in lunar exploration.
Traditionally, scientists believed that the Moon’s surface lacked sufficient oxygen for oxidation processes, typically existing in metallic (Fe⁰) or ferrous (Fe²⁺) states. However, earlier orbital data suggested signs of hematite in polar zones, and samples gathered from the earlier Chang’e-5 mission showed magnetite (Fe₃O₄) created by impacts alongside some signs of oxidized iron in glass formed from impacts. Until now, though, crystalline hematite had never been definitively confirmed. The SPA Basin provided an ideal study area to test these theories.
The research team detected tiny grains of hematite by looking at the lunar soil using high-tech electron microscopy, Raman spectroscopy, and energy-loss spectroscopy. Surprisingly, these hematite grains were not contaminants; they were genuine Moon materials. The scientists propose that massive asteroid impacts generated extreme heat, vaporizing surface materials, and creating a temporary atmosphere rich in oxygen, which then oxidized some minerals, leading to the formation of hematite alongside maghemite and magnetite, as detailed by Phys.org.
This significant discovery may explain the Moon’s various magnetic anomalies, like those found in the northwestern section of the SPA Basin. It underscores the role of collisions in influencing lunar magnetic properties, refuting the earlier belief that the lunar surface lacked oxidation. These findings pave the way for more in-depth investigation into lunar evolution and the connection between magnetic anomalies and significant impact events.
Since Chang’e-6 returned with samples in June 2024, researchers have been uncovering intriguing new information. The mission collected about 4.26 pounds of lunar dust from the SPA Basin, providing vital new details regarding the Moon’s complex geological history. Recent studies indicate that water-rich asteroids are more prevalent than previously thought.
While Earth’s atmosphere tends to break down such asteroids, the Moon’s vacuum-like environment preserves traces of ancient impacts, turning it into a valuable archive. The team successfully isolated seven fragments of carbonaceous chondrites (CI chondrites)—rare meteorites characterized by water and organic matter. By analyzing certain metal ratios, they concluded that these samples did not originate from the Moon, contradicting previous notions that indicated water-rich asteroids were few and far between. This finding suggests the inner solar system experienced regular influxes of such asteroids, as discussed in a PNAS article. Informed by this evidence, researchers hope to tackle enduring questions surrounding the massive impact that shaped the SPA Basin approximately 4.25 billion years ago.
