Density Structure of the Rumker Region in the Northern Oceanus Procellarum: Implications for Lunar Volcanism and Landing Site Selection for the Chang'E-5 Mission

The Rumker region, located in the northern Oceanus Procellarum, is the candidate landing region for China's Chang'E-5 lunar sample-return mission. The area is geologically complex and known for its volcanic activity. To understand the volcanism of the Rumker region, we investigate the 3D crustal density structure of this region using Bouguer gravity data from the Gravity Recovery and Interior Laboratory mission. We applied derivative filters and a 3D density inversion to resolve both the shallow and deep structures in the subsurface. Results indicate that the Rumker region exhibits different modes of emplacement. The Mons Rumker volcanic complex is fed by an intrusion-like structure at a depth of similar to 6-18 km and contains high-density basaltic materials of >3,000 kg/m(3). A quasi-circular mass anomaly that was identified in a previous study with high gravity amplitude (similar to 130 mGal) and high density (> 3,000 kg/m(3)) was also documented in the study region. The quasi-circular mass anomaly feature represents deeper and thicker buried mare basalts with a bowl-shaped geometry formed by an impact event. Based on our geophysical analysis, we propose four landing site candidates for the Chang'E-5 mission that satisfy the geological and geophysical criteria for maximum scientific return. Plain language Summary The Mons Rumker region on the Moon features evidence for multiple volcanic episodes, including some of the youngest lunar mare basalts known to date. To better understand the volcanic activity, we analyzed gravity data from the Gravity Recovery and Interior Laboratory mission with a high resolution of 4.5 km. We used geophysical tools to study both shallow and deep subsurface structures. Our results suggest that the Mons Rumker region features multiple small and large high-density underground bodies, some of which breach the surface. In particular, there could be a large magmatic body at a depth of similar to 6-18 km that fed the surface volcanoes. Our analyses also revealed another circular feature at similar to 7- to 17-km depth with high-density values. As China prepares to send the Chang'E-5 mission to collect drill-hole samples, we combine the results from this study with remote sensing and geological analyses to propose four candidate landing sites that would possibly maximize the scientific return of the mission.