Geological Maps of the Poincaré Basin and the Bose and Bhabha Craters within the South Pole-Aitken Basin: Input for SPARX

GEOLOGICAL MAPS OF POINCARÉ BASIN AND THE BOSE AND BHABHA CRATERS WITHIN THE SOUTH POLE-AITKEN BASIN: INPUT FOR SPARX. C. H. van der Bogert1, W. Iqbal1, L. Wueller1, T. Theiner1, J. Theiner1, H. Hiesinger1, and A. Oetting2. 1Institut für Planetologie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany ([email protected]). 2European Space Agency – European Space Research and Technology Centre, Noordwijk, Netherlands. Introduction: The exploration and sampling of the South Pole-Aitken (SPA) basin is one of the top lunar science and exploration priorities [e.g., 1-5]. Different mission concepts have been developed over the years for the collection and return of materials within the basin, e.g. MoonRise [6] and Endurance [7]. Indeed, the Chinese Space Agency successfully landed two missions on mare deposits within SPA and returned samples from the southern Apollo basin [e.g., 8,9]. Following on earlier work to provide geological context for SPA exploration [10,11], we generated two detailed geomorphological maps of the regions around the Poincaré basin [12] and the Bose and Bhabha craters [13] near the center of SPA. These maps, at a scale of 1:200,000 provide more details of the geospatial distribution of materials formed by different geological processes, which include ancient terra and plains and crater materials spanning much of lunar history. These areas contain provisional traverses investigated in the Endurance mission concept [7]. Geological units: We identified geomorphological units, including terra, plains, and crater units, across the two mapped regions (Figures 1,2). Terra units, often characterized by rugged, elevated terrain, represent a mixture of ancient heavily cratered materials [e.g., 14]. pNt (pre-Nectarian terra) are composed of undifferentiated, elevated materials of pre-Nectarian age, which may have originated from impact craters or could represent the floor of SPA itself. Terra southeast of Bhabha crater has been interpreted as a mafic mound [e.g., 15]. Its geomorphology does not, however, distinguish it from other exposures of the pNt. NpNt (Nectarian pre-Nectarian terra) are characterized by undifferentiated craters and ejecta material, exhibiting significant degradation due to subsequent impact cratering. Plains units are extensive, relatively flat regions often characterized by a smooth, subdued topography [e.g., 14]. These units may be formed by various processes, including volcanic activity or the emplacement of impact ejecta. NpNlp (Nectarian pre-Nectarian light plains), observed in low-lying areas, are less hummocky than the NpNt terra unit. Given their low iron abundance, they likely represent basin ejecta deposits. Ilp (Imbrian light plains) are predominantly located in low-relief regions and on crater floors. This material is presumed to comprise ejecta from multiple impact events. Figure 1. Geomorphological map of the Poincaré basin region [12]. Idp (Imbrian dark plains) are observed in areas of low relief and on crater floors. Due to their high iron content, they are interpreted as mare basalt deposits. Crater materials are clearly associated with impact basins or craters, due to their distinctive morphologies, including crater rims, ejecta deposits, and ray materials. pNPr (Pre-Nectarian Poincaré rim) marks the distinctive multi-ring structure of Poincaré basin. NpNc (Nectarian pre-Nectarian crater material) is characterized by highly degraded crater rims with indistinguishable ejecta from several craters. LIc (Lower Imbrian crater material) is characterized by identifiable crater rims and ejecta deposits. However, the crater rims are more degraded that those of UIc and Ec. Some of the smaller late Imbrian craters may be secondary craters from Orientale basin [e.g., 10,16]. UIc (Upper Imbrian crater material) shows sharper crater rims and ejecta than in LIc. Ec (Eratosthenian crater material) are crater materials that exhibit a fresher morphology compared with LIc and UIc, but do not exhibit crater rays. Sc (Secondary crater material) is an undifferentiated unit that shows the distribution of secondary crater chains and clusters across many units. Conclusions: Geomorphological maps are important higher level data products for the planning and operation of both science and exploration missions. These maps of regions of SPA support major goals defined in numerous strategies for the exploration of the Moon. For example, they can be used to inform the work of NASA’s South Pole-Aitken Basin Sample Return and eXploration (SPARX) Science Definition Team that has recently been selected [17]. References: [1] NRC (2007) Scientific Context for Exploration of the Moon. [2] LEAG (2017) Advancing the Science of the Moon. [3] Crawford et al. (2012) Planetary & Space Science 74, 3-14. [4] Pieters et al. (2018) Transformative Lunar Science, SSERVI, NASA. [5] ESA (2019a) ESA Strategy for Science at the Moon. [6] Jolliff et al. (2012) LEAG, 3047. [7] Keane et al. (2021) Endurance Mission Concept Study Report, NASA. [8] Liu et al. (2021) Space Science Reviews 217, 6. [9] Zeng et al. (2023) Nature Astronomy 7, 1188. [10] Ivanov et al. (2018) JGR 123, 2585. [11] Poehler et al. (2020) LPSC 51 #1951. [12] Hiesinger et al. (2025) LPSC 56, #1880. [13] Iqbal et al. (2025) LPSC 56, #1062. [14] Wilhelms et al. (1987) USGS Prof. Pap. 1348. [15] Moriarty and Pieters (2015) Geophysical Research Letters 42, 7907. [16] Hiesinger and Tanaka (2020) The Planetary Time Scale, Elsevier. [17] https://science.nasa.gov/lunar-science/sparx/. Figure 2. Geomorphological map of the Bose and Bhabha craters region [13].