Exploration of the Rubin Crater on the Amundsen Crater Rim: A Lunar Science Perspective

EXPLORATION OF RUBIN CRATER ON THE AMUNDSEN CRATER RIM: A LUNAR SCIENCE PERSPECTIVE. L. Wueller1, W. Iqbal1, X. Xu1,2, H. Brown3, C. H. van der Bogert1, T. Hu2, Z. Kang2, and H. Hiesinger1; 1Institut für Planetologie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany ([email protected]), 2China University of Geosciences, Beijing, China, 3School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA. Introduction: Various international space agencies aim to explore the Moon’s south polar region via crewed and uncrewed landing and exploration missions. Scientific interest in the region is related to its to-date unexplored terrain, its proximity to the ancient South Pole-Aitken (SPA) basin, potential resources in permanently shadowed regions (PSRs), and the presence of regions that receive sunlight for most of the lunar year. To support these future exploration efforts and maximize scientific return, a solid geologic understanding of the region is essential. In this context, we present a design reference mission (DRM) to Rubin crater (~4 km diameter), situated on a massif along the northwestern rim of Amundsen crater (Fig. 1), which is thought to be a remnant of the SPA basin rim [1,2]. The Rubin crater region offers favorable conditions for landing and exploration, making it an optimal site for testing operations at a south polar landing location before undertaking more challenging missions, such as a landing on the rim of Shackleton crater. Methodology: To produce a high-resolution geologic map and identify candidate landing sites, we utilized data from the Lunar Reconnaissance Orbiter Narrow Angle Camera (LRO-NAC) [3] to generate NAC mosaics with a resolution of 1 m/pixel [4], which were topographically controlled to LRO Lunar Orbiter Laser Altimeter (LOLA) digital elevation models (LDEM) [5]. Additionally, we used the LDEM to generate terrain slope and artificially illuminated hillshade maps to mitigate potential biases caused by challenging illumination conditions. Geologic Map: To support landing site selection, mission planning, and the definition of science objectives, we present the highest resolution geologic map to date of the Rubin crater region on the mountainous northwestern rim segment of Amundsen crater [7]. By integrating our newly developed local map with the existing regional map of Amundsen crater [2], we can extrapolate observations from the landing site to broader areas in the region and vice versa. The study area is dominated by material associated with the adjacent Amundsen crater, which formed ~4.04 Ga ago during the Nectarian period excavating material to a depth of ~8 km [2]. These materials, concentrated in the ejecta blanket covering the adjacent SPA massif, have since been modified by subsequent impacts, including the formation of the ~4 km diameter Rubin crater ~1.58 Ma ago in the Eratosthenian period [7]. Rubin crater is surrounded by boulders up to a few meters in size, which are mapped as potential sampling targets. Engineering Constraints for Exploration: Welldefined engineering constraints are prerequisites for a successful exploration program, as they determine the feasibility and safety of landing and mobility at a given site. To ensure mission safety, the landing site slope should not exceed 7°, while rover traverses should remain below 20° [8], although Apollo astronauts reported rover slippage at slopes of approximately 15° [9]. To guarantee adequate energy supply for the exploration equipment and maintain timely communication with the Mission Control Center on Earth, both the Sun and Earth should be visible for at least 35% of the lunar year [2]. However, illumination conditions vary throughout the lunar year and are highly dependent on mission timing. Based on these criteria, we have identified three candidate landing sites where landing and operational hazards are minimized (Fig. 2). Potential Science Targets: A rover could traverse distances of up to 10 km from the landing site [9], whereas an astronaut without additional roving equipment is limited to a ~2 km radius around the landing site [10]. Candidate landing sites A (76.128° E, 82.719° S) and B (76.688° E, 82.485° S) are both located on the Amundsen ejecta material covering the massif, while candidate landing site C (78.353° E, 82.679° S) is closest to the rim of Rubin crater and is the only candidate landing site located on Rubin crater’s ejecta blanket. For each candidate site, we present multiple traverse options for walking EVAs, robotic rover exploration, and EVAs utilizing the Lunar Roving Vehicle (LRV), addressing a diverse range of scientific objectives (Fig. 2) [7]. Several targets of scientific interest, such as boulders, PSRs, and small fresh craters, are located along the traverses. Traverses for walking EVAs follow shallow slopes (<7° for most of the distance) and never exceed 15° to minimize metabolic stress, while rover traverses may include short sections with slopes up to 20°. Detailed descriptions of the candidate landing sites and their traverse options are provided in [7]. Conclusions: We produced a high-resolution geologic map of the Rubin crater region on the northwestern rim of Amundsen crater, previously identified as a promising exploration site for future missions [e.g., 2]. Additionally, we conceptualized a design reference mission to emphasize the region’s potential to address several key science goals outlined by the National Research Council [11], which could elucidate our understanding of the Moon’s history and evolution. If the Rubin impact penetrated the local Amundsen ejecta and reached the underlying SPA massif, the resulting ejecta materials – both from Rubin crater and the Amundsen ejecta covering the massif – would be prime sampling targets for SPA-derived materials. These samples could provide insights into early Solar System dynamics, lunar differentiation, and serve as anchor points for the lunar chronology function [11,12]. Furthermore, the Rubin region contains PSRs of varying sizes and temperatures, offering opportunities to study the distribution, composition, and thermal stability of lunar volatiles. Given its ability to address a broad range of scientific objectives while providing favorable conditions for landing and exploration, the Rubin crater region can serve as an ideal test site for operations at a south polar location before attempting more challenging missions, such as a Shackleton crater rim landing. References: [1] Krasilnikov et al. (2023) Icarus, 394. [2] Wueller et al. (2024) PSJ, 5(6), 147. [3] Robinson et al. (2010) SSR, 32(1). [4] Collins et al. (2024) LPSC, 1774. [5] Barker et al. (2023) PSJ, 4(9), 183. [7] Wueller et al. (2025) submitted to Adv. in Space Res. [8] Kring and Durda (2012) LPI. [9] Iqbal et al. (2024) Acta Astronautica, 223. [10] NASA (2019) HLS Requirements Document, HLSRQMT-001. [11] National Research Council (2007) The Scientific Context for Exploration of the Moon, National Academic Press. [12] Neukum et al. (1983) LMU München, Germany.