Morphological characteristics and digital generation of millimeter-scale particles in the lunar soil of Chang'e-5

The millimeter-scale lunar soil particles from the CE-5 mission exhibit a complex morphology, including pronounced angularity and particle agglomeration caused by high-temperature sintering during space weathering. This distinctive particle morphology has a significant impact on the physical and mechanical properties of its assemblages, serving as a critical factor influencing the engineering behavior and resource utilization of lunar soil. Accurately reproducing this complex shape remains challenging but is critical for particle-scale simulations and weathering layer mechanics studies. In this study, we quantitatively characterise the morphology of CE-5 particles via five shape descriptors, including a five-dimensional morphological framework of particle size, sphericity, convexity, aspect ratio, and Wadell roundness, to systematically quantify the shape of lunar soil particles. A digital particle generation procedure based on database matching and a complex Fourier descriptor (CFD), which is capable of creating nonsingular digital particles with target shape characteristics, was developed. The mean values of particle size, sphericity, convexity, aspect ratio and roundness for real particles were 0.84, 0.78, 0.92, 0.76 and 0.12, respectively, whereas the corresponding parameters for generated particles were 0.86, 0.82, 0.96, 0.80 and 0.15, respectively. In the normalised morphometric five-dimensional feature space, the overall Wasserstein distance is as low as 0.014, indicating that the generated particles are in good agreement with the real samples and that their morphological parameters are highly matched with the measured data. These findings demonstrate the effectiveness of CFD-based replication of lunar weathering layer morphology and provide a practical way to generate particles for lunar modelling and engineering applications.来自嫦娥五号（CE-5）任务的毫米级月球土壤颗粒展现出复杂的形貌特征，包括显著的棱角性，以及空间风化过程中高温烧结引发的颗粒团聚现象。这种独特的颗粒形貌对其颗粒集合体的物理力学性能具有显著影响，是影响月球土壤工程特性与资源利用的关键因素。精准复现这种复杂形貌仍存在挑战，但对于颗粒尺度模拟与风化层力学研究而言至关重要。本研究通过五类形状描述子定量表征CE-5颗粒的形貌特征，以粒径、球形度、凸度、长宽比以及瓦德尔圆度（Wadell roundness）构建五维形貌框架，以此系统量化月球土壤颗粒的形状特征。本研究开发了一种基于数据库匹配与复傅里叶描述子（Complex Fourier Descriptor，CFD）的数字颗粒生成方法，该方法能够生成具备目标形貌特征的非奇异数字颗粒。真实颗粒的粒径、球形度、凸度、长宽比与圆度的平均值分别为0.84、0.78、0.92、0.76与0.12，而生成颗粒的对应参数分别为0.86、0.82、0.96、0.80与0.15。在归一化后的五维形貌特征空间中，整体瓦瑟斯坦距离（Wasserstein distance）低至0.014，表明生成颗粒与真实样本匹配度良好，其形貌参数与实测数据高度吻合。上述研究结果证明了基于复傅里叶描述子的月球风化层形貌复现方法的有效性，同时为月球建模与工程应用中的颗粒生成提供了切实可行的途径。