Scientists discover impact magnetite in lunar soil delivered by Chang’e 5

(ORDO NEWS) — A research team from the Chinese Academy of Sciences conducted an electron microanalysis of spherical grains of iron sulfide in lunar soil returned by the Chang’e-5 mission and confirmed the presence of submicroscopic magnetite of impact origin.

Magnetite plays an important role in planetary science in dealing with ancient magnetic fields and indicators of life.

During the Apollo era, some studies revealed the widespread presence of submicroscopic magnetite-like phases in lunar soil, but there was no further mineralogical evidence for the presence of widespread magnetite crystals.

In the lunar soil mined by Chang’e-5, magnetite-bearing spherical grains of iron sulfide (<2 µm in diameter) were observed.

Transmission electron microscopy observations showed that spherical iron sulfide grains were characterized by rings of equidistant pure iron tentacles at the grain edges and ubiquitous submicroscopic particles of magnetite and metallic iron, which were deposited in an internal troilite-pyrrhotite structure.

Combining these observations with thermodynamic calculations, the researchers found that during major collisions on the Moon, a reaction occurred that allowed FeO dissolved in iron sulfides to form submicroscopic magnetite and metallic iron through a eutectic reaction (4FeO = Fe3O4 + Fe).

This first discovery of submicroscopic magnetite of impact origin is direct evidence that magnetite can be widely distributed in the thinnest lunar soil.

Lunar magnetic anomalies have been a mystery since the days of Apollo, and their origins are still debated. Previous studies have only established the relationship between large impact spikes and magnetic anomalies, but have not focused on material transformation during impact.

“In our study, another important ferromagnetic mineral (magnetite) was discovered, formed as a result of a eutectic reaction during impact processes on the Moon,” said Professor Li Yang, author of the study.

“Due to the high magnetic susceptibility of magnetite and metallic iron, impact processes would greatly reduce the thickness requirements for lunar soil for lunar magnetic anomalies.”


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