Evaluation of lunar soil sampling disturbance based on penetration resistance method

Introduction To investigate the impact of surface sampling operations on the physical and mechanical properties of lunar soil—defined as the granular, sub-centimeter-sized fraction of the lunar regolith—and to mitigate design errors in sampling missions that arise from neglecting such disturbance, we conducted sampling disturbance experiments using the CUG-1A lunar soil simulant. Methods The degree of lunar soil disturbance was evaluated based on the change in penetration resistance of a standard probe inserted into the soil before and after sampling. Results The experimental results indicate that the bucket width, sampling depth, sampling speed, and (for shovelling) the entry angle all significantly affect the disturbance degree. Discussion The shovelling action, a linear penetration-and-lift operation, predominantly induces a compaction effect on the lunar soil simulant. In contrast, the digging action, an arcuate scooping operation, causes compaction during the initial phase but generates a distinct loosening effect at the motion endpoint. The parameter combination that minimizes disturbance for the shovelling experiment is a bucket width of 4 cm, sampling depth of 2 cm, speed of 50 mm/s, and entry angle of 45°. For the digging experiment, the optimal combination is a bucket width of 4 cm, sampling depth of 3.5 cm, and speed of 50 mm/s.