Gravity Observations of the Aristarchus Plateau on the Moon: Implications for the Volcanic and Impact Histories of the Plateau

Introduction The Aristarchus Plateau (Figure 1) is a distinctive, geologically complex volcanic highland in northern Oceanus Procellarum. It is roughly diamond shaped, 170 by 220 km across, and up to 2 km higher than the surrounding mare [1, 2]. The roughly linear edges of the plateau suggest that it is fault bounded. The plateau edges are essentially radial and concentric to the center of the Imbrium basin [1, 3] and the northeastern margin of the plateau lies on or very close to an Imbrium basin ring [3, 4]. These observations suggest that uplift of the plateau is related to the Imbrium impact. Aristarchus contains a high density of diverse volcanic landforms. Much of the plateau is covered by a low albedo unit, interpreted as due to deposition of volcanic glass in a pyroclastic eruption [5-9]. These deposits cover 49,000 km, which is 5 times the area of the next largest lunar pyroclastic deposit [10]. 36 sinuous rilles occur in the region, demonstrating that effusive volcanism was also important [11]. Detection of the radioactive gas Rn indicates that some type of on-going out-gassing from the interior is occurring in this region [12, 13].