Buried Ice Deposits in Lunar Polar Cold Traps Were Disrupted by Ballistic Sedimentation

Abstract

The NASA Artemis program will send humans to the lunar south polar region, in part to investigate the availability of water ice and other in situ resources. While trace amounts of ice have been detected at the surface of polar permanently shadowed regions (PSRs), recent studies suggest that large ice deposits could be stable below cold traps in the PSRs over geologic time. A recent study modeling the rate of ice delivery, ejecta deposition and ice loss from cold traps predicted that gigatons of ice could be buried below 100s of meters of crater ejecta and regolith. However, crater ejecta vigorously mix the target on impact through ballistic sedimentation, which may disrupt buried ice deposits. Here, we developed a thermal model to predict ice stability during ballistic sedimentation events. We then modeled cold trap ice and ejecta stratigraphy over geologic time using Monte Carlo methods. We found that ballistic sedimentation disrupted large ice deposits in most cases, dispersing them into smaller layers. Ice retention decreased in most cases, but varied significantly with the sequence of ejecta delivery, particularly from basin‐forming events. Over many model runs, we found that south polar craters Amundsen, Cabeus, and Cabeus B were most likely to retain large deposits of ice at depths up to 100 m, shallow enough to be detectable with ground‐penetrating radar. We discuss these findings in the context of the imminent human exploration activities at the lunar south pole.

The Age and Evolution of Lunar Micro Cold Traps at the Scale of Surface Exploration

“…These processes destroy craters but can sequester ice from the hostile and active surface. Ballistic sedimentation of ejecta has been shown to destabilize rather than preserve ice at meters to many‐kilometers scales (Tai Udovicic et al., 2023); however, there is a need for a better understanding of the smaller scale and lower energy process of degrading decimeters‐scale micro cold traps.…”

Geologic History of the Amundsen Crater Region Near the Lunar South Pole: Basis for Future Exploration

“…The extent of areas with an ice stability depth of <1 m was significantly smaller under paleotemperature conditions (Siegler et al 2016), which may explain the absence of water-ice detections by M3 and Mini-RF CPR despite Amundsen PSR temperatures remaining below 110 K. This would imply that no ice has accumulated in newly formed cold traps, suggesting absent or slow accumulation of volatiles since the Moon's axis shifted (Siegler et al 2016). Furthermore, thermal modeling of ice stability during ballistic depositional events, i.e., impacts, over geologic timescales predicts that Amundsen crater is capable of retaining large ice deposits to depths of 100 m (Tai Udovicic et al 2023), which is shallow enough to be detectable with ground-penetrating radar.…”

YOLO-Crater Model for Small Crater Detection

“…As circular geomorphological features, craters are formed by the collision of small celestial bodies at high speed. They have great significance for geological age estimation of the Moon [1,2] and Mars [3], terrain and evolutionary history research [4], mineral resource assessment [5], safe landing [6,7], landing site selection and obstacle avoidance for rovers [8], evaluating the influence of the crater abundance on the ice occurrence [9] in the lunar polar Permanently Shadowed Regions (where ARTEMIS [10] will land), and even subsurface exploration [11]. Hence, crater detection has always been a hot topic.…”