Researchers have identified a previously unknown magnetic mineral phase in lunar samples returned by China’s Chang’e-6 mission. The study, conducted by Prof. Haifeng Du’s team at the High Magnetic Field Laboratory in Hefei and published in the Proceedings of the National Academy of Sciences on September 16, focused on analyzing impact glass from the lunar soil.
Using advanced microscopy and chemical analysis techniques, the research team discovered nanoscale particles of face-centered cubic γ-Fe embedded throughout the glass samples. This particular form of iron is typically stable only at high temperatures and normally transforms into a different iron structure called α-Fe as materials cool. The findings suggest that the extreme conditions generated during lunar impacts may allow this unstable iron phase to persist on the Moon’s surface. The researchers identified several factors that could stabilize the γ-Fe structure, including the presence of carbon and other elements, the rapid cooling of material ejected during impact events, and protection provided by the surrounding glassy material.
Through electron holography analysis, scientists determined that larger γ-Fe nanoparticles can maintain a stable single-vortex magnetic state and retain consistent magnetic responses when exposed to external magnetic fields. These properties suggest that γ-Fe particles could function as previously unrecognized recorders of magnetic information trapped within lunar materials, potentially preserving evidence of conditions that existed when the Moon maintained its ancient magnetic field.
The discovery expands the known inventory of magnetic minerals found in lunar samples. Since γ-Fe and α-Fe form under different conditions and display distinct magnetic behaviors, both phases could independently preserve information from different stages of lunar impacts. Researchers indicate that additional work will be required to determine the extent to which these minerals can illuminate details about the Moon’s historical magnetic field and how it changed over geological time.
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