The Moon, known for its grey, pockmarked surface, also exhibits bright patches called lunar swirls, which have puzzled scientists since their discovery in the 1600s. One such swirl, Reiner Gamma, remains a mystery. A recent study from scientists at Stanford University and Washington University in St. Louis (WUSL) suggests a new explanation for these lunar swirls.
Unlike Earth, the Moon no longer generates a global magnetic field, leaving it vulnerable to solar winds that darken the lunar surface over time due to chemical reactions. However, some pockets on the Moon appear to be protected by mini magnetic fields. Interestingly, every light-shaded lunar swirl scientists have found coincides with one of these local magnetic fields.
However, not all rocks within these magnetic fields are reflective, nor do all magnetic fields on the Moon contain swirls. Some researchers have suggested that micrometeorite impacts could create local magnetic fields, but scientists at Stanford and WUSL argue that some other force has ‘magnetized’ the lunar swirls, deflecting solar wind particles.
Planetary scientist Michael Krawczynski at WUSL admits that impacts could cause magnetic anomalies, but he suggests that forces from beneath the crust could also be at work. He proposes that slowly cooling magma underground, rich in a mineral called ilmenite, could produce a powerful magnetic field.
Experiments conducted by Krawczynski and his colleagues show that under the right conditions, the slow cooling of ilmenite can stimulate grains of metallic iron and iron-nickel alloys within the Moon’s crust and upper mantle to produce a magnetic field. This effect, they conclude, “could explain the strong magnetic regions associated with lunar swirls.”
NASA is planning to send a rover to the Reiner Gamma swirl in 2025 as part of their Lunar Vertex mission, which could provide the evidence needed to solve this mystery. The study was published in the Journal of Geophysical Research: Planets.
