Rare Iron Crystal Form Discovered in Lunar Samples Preserves Ancient Magnetic History

Scientists analyzing soil samples from China's Chang'e-6 lunar mission have identified a previously unknown form of metallic iron called gamma-iron embedded within impact glass particles on the Moon's surface. This nanoscale iron mineral preserves a stable magnetic signal and may serve as a record of the Moon's ancient magnetic field, which no longer exists today. The discovery, published in the Proceedings of the National Academy of Sciences, provides new insights into how the lunar magnetic environment changed over geological time.

Scientists have long recognized that the Moon once possessed a magnetic field that has since vanished. By examining magnetic minerals trapped within lunar rocks and soil, researchers can piece together the history of how this planetary magnetism diminished over time. The Chang'e-6 mission, which collected samples from the Moon's surface, provided material containing previously unidentified iron structures that may serve as especially sensitive records of these ancient magnetic conditions.

The gamma-iron particles discovered in impact glass formed under extreme conditions created by asteroid or meteorite collisions on the lunar surface. These nanoscale structures remained locked in a stable magnetic state, potentially preserving information about the magnetic environment that existed when the impacts occurred. This discovery expands the toolkit scientists have for reconstructing the Moon's geological and magnetic history across different time periods.