GEOLOGIC MAPPING OF THE APOLLO LUNAR QUADRANGLE (LQ-24), EASTERN SOUTH POLE-AITKEN BASIN

The South Pole-Aitken (SPA) basin is the largest (~2,500 km across) and oldest (pre-Nectarian) confirmed impact basin on the Moon. This mapping effort integrates high-resolution images and topographic and spectroscopic remote sensing data from recent lunar missions to construct the first geologic map of eastern SPA since the 1970s.

The geologic map of LQ-24 (30° to 60°S latitude, 180° to 240°E longitude) covers the eastern half of SPA, and is being prepared in Lambert conformal conic projection. We are using ArcGIS (v. 10.8) to map at a scale of 1:250K, which will yield a printed map at 1:2.5M scale. The Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) mosaic (100 m/pixel) is our primary basemap, which is supplemented with derived Lunar Orbiter Laser Altimeter (LOLA) products (e.g., DEM, hillshade) and Kaguya morning and evening Terrain Camera (TC) mosaics to assist in our mapping. This mapping effort follows the standards set by the United States Geological Survey (USGS) and will produce a Scientific Investigations Map (SIM) that not only will complement geologic maps of neighboring quads but will also be key in support of future missions in identifying exploration targets for possible crewed or robotic missions.

Highland terrain covers the northeastern corner of the map area, which is formed in part by SPA’s rim and heavily cratered feldspathic highlands. The floor of SPA covers the remainder of the quad. The highland terrains are heavily cratered relative to the floor of SPA. The map area exhibits ~15 km of relief between the rim of SPA (~6.7 km) and its floor (~-8.7 km). The floor of SPA, and the floors of many of the craters that impacted the floor of SPA (e.g., Apollo, Leibnitz, Oppenheimer), display surfaces that range in albedo from dark to bright, and texture from smooth to rugged. The surface displays predominantly low albedo, or dark) and moderate albedo materials. Dark materials occur mostly on the floor of Apollo and in a few small areas on the floor of SPA, whereas moderate albedo materials are more abundant throughout SPA. At LROC WAC scales, the dark material and portions of the moderate albedo material appear relatively smooth; however, some areas of the moderate albedo material are rugged.