Recently, Chinese researchers identified, for the first time, micrometer-scale crystalline Fe2O3 in the forms of hematite (α-Fe2O3) and maghemite (γ-Fe2O3) in lunar soils, formed by large-scale impact events, the China National Space Administration (CNSA), Shandong University, and the Chinese Academy of Sciences jointly announced on Sunday.

The discovery is based on analysis of lunar soil samples returned by the Chang'e-6 mission from the South Pole-Aitken (SPA) Basin, providing credible evidence for the presence of Fe2O3 on the lunar surface and challenging the traditional understanding of lunar surface redox states.

This finding, published in the journal Science Advances, will offer important scientific support for future lunar research and deepen understanding of the moon's evolutionary history.

According to the study, the formation of hematite is likely closely linked to past large-scale impact events on the moon. Such impacts can generate a heterogeneous vapor environment characterized by locally elevated oxygen fugacity, where Fe2+ ions are oxidized to higher valence states, leading to the desulfurization of troilite (FeS). Through subsequent vapor-phase deposition, this process forms micrometer-scale crystalline hematite particles.

Notably, the intermediate products of these reactions – magnetite and maghemite – are magnetic and may serve as mineral carriers of the magnetic anomalies surrounding the South Pole-Aitken (SPA) Basin on the lunar farside.

The research provides the first sample-based confirmation that highly oxidizing minerals such as hematite can exist on the lunar surface despite its reducing environment. It also sheds new light on the moon's redox state and the reason for the generation of its magnetic anomalies.

The SPA Basin, where Chang'e-6 landed, is the largest and oldest known impact basin on any rocky body in the solar system. The scale of the impact that formed it far exceeded that of other regions on the moon, providing a unique setting for studying exceptional geological processes. The successful return of samples from within the basin's interior by the 2024 Chang'e-6 mission laid the foundation for this breakthrough discovery.