Magnetic Anomalies Near the Lunar South Pole and Their Consequences

We report improved mapping of crustal magnetic anomalies near the lunar poles using a combination of Lunar Prospector and Kaguya orbital magnetometer data.  In agreement with previous results, a concentration of moderately strong magnetic anomalies is centered approximately on the south polar region.  In contrast, only a single verified anomaly is present in the north polar region.  Published analyses of Kaguya spectral profiler and LOLA albedo data have shown that an area of relatively low optical maturity and high surface albedo is present in the south polar region whereas the north polar region is mostly optically mature. Comparing our magnetic field maps to published albedo maps (D. Moriarty and N. Petro, JGR, 2024), possible curvilinear albedo markings (“swirls”) of the Reiner Gamma class are present where the strongest anomalies near the south pole are found. In the north polar region, a single albedo anomaly is present just poleward of the single magnetic anomaly. In view of previous work showing that solar wind ion deflection associated with crustal magnetic fields can lead to surface optical immaturity, higher surface albedo, and swirl formation, the empirical evidence reported here supports the hypothesis that the magnetic anomalies near the south pole are capable of significant solar wind ion flux reductions. 

Previous analyses of Moon Mineralogy Mapper (M³) data have also found that more inferred water ice exposures are present near the south pole than near the north pole (S. Li et al., PNAS, 2018).  We have previously reported particle-in-cell simulations of the surface plasma flux and water ice lifetimes against solar wind ion sputtering in this region, taking into account crustal magnetic fields as well as topography (J. Deca et al., 2025 LPSC; 2026 LPSC).  These simulations demonstrate a correlation between areas of long sputtering lifetimes and areas with more numerous water ice exposures.  Further simulations using the improved crustal field maps are in progress and will be presented at the meeting.