Lunar swirls are bright, curved regions on the Moon’s surface. Though lunar swirls are known to be associated with areas where the magnetic field suffusing the Moon’s crust is unusually strong, it’s not clear exactly what causes lunar swirls. Does the stronger magnetic field protect the lunar surface from bombardment by the incessant solar wind? Have fine-grained, reflective lunar soils accumulated in these regions? Or do the swirls perhaps reflect the aftermath of an encounter with a comet that swept certain areas of the Moon’s surface clean, then snowed fine particles across the surface? To uncover the origins of lunar swirls, a team led by Mallory Kinczyk (The Johns Hopkins University Applied Physics Laboratory) investigated the three swirl areas shown above. Each region represents a different type of surface material and geography, including lunar seas and highlands. The team carried out a detailed photometric analysis and modeling of data from the Lunar Reconnaissance Orbiter Camera Narrow Angle Camera to determine the properties of the lunar soils and investigate existing hypotheses for swirl formation. Overall, the team’s results support the hypothesis that the anomalously strong magnetic fields embedded within the Moon’s crust shield the surface from solar wind impacts, creating the sinuous swirls seen today.
Citation
“Photometry of Lunar Swirls in Comparison to Fresh Crater Ejecta,” Mallory J. Kinczyk et al 2025 Planet. Sci. J. 6 57. doi:10.3847/PSJ/adafa6