¹Chuansheng Xu, ^1,2Yifei Cui, ¹Ao Luo, ¹Guodong Wang, ^1,3Lu Jing, ⁴Jiayan Nie
Journal of Geophysical Research: Planets, 131, e2025JE009536 Link to Article [DOI: 10.1029/2025JE009536]
¹State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing, China
²Key Laboratory of Hydrosphere Sciences of the Ministry of Water Resources, Tsinghua University, Beijing, China
³Shenzhen International Graduate School, Institute for Ocean Engineering, Tsinghua University, Shenzhen, China
⁴School of Civil Engineering, Wuhan University, Wuhan, P. R. China
Published by arrangement with John Wiley & Sons

Lunar lithic fragments (micrometer–millimeter scale) mainly consist of basalt, breccia, agglutinates, leucocratic fragments, and glass. Their morphology, surface properties, and frictional behavior fundamentally control the mechanical characteristics of lunar regolith, which can be effectively characterized by the angle of repose (AoR)—a simple and intuitive parameter obtained through rapid experiments that reflects the frictional, flow, and stability features of granular materials. This study analyzes five representative lithic fragment types from Chang’e−6 samples (30 particles) to investigate how morphology, surface energy, and friction jointly influence the AoR and develops a predictive model coupling multi-scale particle parameters. Results show that for particles larger than 200 μm, complex shapes (Overall regularity 0.6) and high friction coefficients (0.55) increase AoR by 10°–20° through enhanced interlocking. For smaller particles, surface energy dominates interparticle forces but is constrained by surface roughness, reducing its effective range. Under lunar gravity, the effects of morphology and friction are weakened, and the threshold size separating friction-shape-dominated and adhesion-dominated regimes shifts from ∼100 μm on Earth to ∼200 μm on the Moon. In coarse-grained assemblages, agglutinates dominate the variation in AoR, while glass content is weakly negatively correlated with it. The model reveals intrinsic mechanisms of lunar soil behavior and provides a theoretical basis for regolith handling and construction in future lunar missions.