MAGNETIC AND GRAVITY SURVEYS FOR IMAGING THE GEOLOGY OF THE SOUTH POLE-AITKEN BASIN ON THE MOON

Magnetic and gravity anomalies on the Earth are often the consequence of igneous activity, and provide insight into the processes active during that igneous activity. An abundance of dikes should exist in the crust of the Moon, just as on the Earth. It is expected that most dikes were probably emplaced early in the Moon’s history, before compressive stress reached present levels, and that most of those dikes reside in the lower crust. Dike swarms are common in the Earth’s crust and they often have magnetic signatures acquired as their magnetic minerals cool below their Curie temperature. We report and interpret observations over the South Pole-Aitken (SPA) basin from three satellite missions to map the magnetic and gravity fields of the Moon. This far-side basin is one of the largest and oldest in the solar system, and it’s impact origin set the stage for many of the Moon’s first-order characteristics. A set of WNW-trending linear to arcuate magnetic features, evident in both the radial and scalar magnetic field observations, covers much of a 1000 km wide region centered on the NW portion of SPA. We infer that the magnetic features represent dike swarms that served as feeders for mare basalts on the surface. Gravity observations also reveal the presence of dikes in the SPA region, but those dikes have a variety of trends, and are not identical with the magnetically identified dikes. We discuss possible scenarios to explain these observations.