¹A. C. Zhang, ¹T. R. Du, ¹L. Zhang, ¹Z. G. Zhang, ²Q. Zhou, ¹R. C. Wang
Journal of Geophysical Research: Planets, 131, e2026JE009945 Link to Article [DOI: https://doi.org/10.1029/2026JE009945]
¹State Key Laboratory of Critical Earth Material Cycling and Mineral Deposits, School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
²Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

Lunar mantle material could have been excavated during the formation of South Pole-Aitken (SPA) basin and is potentially present in the Chang’e-6 lunar soil retrieved from the basin. Here, we report the petrography and mineral composition of highly magnesian olivine and enstatite in Chang’e-6 lunar soil. Most of the highly magnesian olivine grains have compositions consistent with source rocks from impact-related norites and Mg-suite rocks, while some lithic clasts containing highly magnesian olivine grains can be attributed to impact-induced melting and recrystallization with material contribution from chondrite meteorite. Some highly magnesian olivine grains display a high-Ni feature with high Al₂O₃, Cr₂O₃, and CaO contents, which could be attributed to impact origin rather than lunar mantle origin. Most of the highly magnesian enstatite grains have compositions comparable to those from impact-related SPA noritic clasts, indicating that they probably share similar source rocks; whereas, some highly magnesian enstatite grains in Chang’e-6 lunar soil are probably derived from Mg-suite rocks. The observations suggest that there are no unambiguous mantle minerals in Chang’e-6 lunar soil, which are instead potentially found in the regions surrounding the SPA basin in the future. We find that Chang’e-6 highly magnesian enstatite grains show systematically lower TiO₂ contents than those from the Moon’s near side and suggest that the relative Ti-depletion in highly magnesian enstatite from Chang’e-6 lunar soil could be due to high modal abundance of enstatite in their parent rocks, consistent with the orthopyroxene dominance in the far-side lunar mantle.

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.