月壤是大部分月球遥感探测的对象。半个多世纪前的月球探测发现月壤岩芯中普遍存在大量的纹层结构，但由于纹层结构在粒径和组分上没有标型特征，其成因机理未知。该问题一直是制约月壤成因机制研究的一个关键短板。近年来，在嫦娥三号获取的月壤雷达数据中也发现了大量的纹层结构，但其介电性质和物质属性未知。申请人前期的研究表明这些纹层结构是研究月壤形成和演化的全新窗口。本项目拟以嫦娥三号和四号的高频探月雷达数据为基础，通过约束背景月壤的介电参数、识别提取纹层结构、开展大样本的月壤模型正演计算、对比研究高分辨率区域地形地貌，参考撞击挖掘和弹道沉积过程，约束月壤中纹层结构的物理性质和探讨其可能的成因机制。该工作将为完善月壤形成和演化的认识提供新视角，也将直接服务于我国嫦娥五号采样返回任务的物源追踪任务。

Most remote sensing for the Moon was restricted within the depth of lunar regolith. More than half a century ago, the Apollo and Luna missions have revealed the common occurrence of laminar structures in the lunar regolith. However, the laminas have no typomorphic characteristics in terms of average grain sizes, petrology, and geochemistry compared to normal regolith, the origin of the laminas has been unclear. This problem strongly affects our understanding on the formation and evolution of lunar regolith. Recently, similar multi-layered structures were observed in the radargram obtained by the high-frequency lunar penetrating radar carried by the Chinese Chang'e-3 mission. However, the cause and possible physical characteristics of materials in the laminar were not investigated. Our previous studies have suggested that these features in the radargram are important to complete our understanding of the formation and evolution of lunar regolith. In this proposal, data returned by the high-frequency lunar penetrating radar onboard both the Chang'e-3 and Chang'e-4 missions will be used to investigate the identity of the laminars in the regolith. We will calculate the dialectic properties of the background regolith. Dedicated regolith models containing the laminar structures will be constructed, and large samples of modeling will be performed to estimate the dialectic properties, and thus density and porosity of the laminars. The results will be compared to high-resolution surface morphology, and impact excavation and ballistic sedimentation models will be used to deduce the origin of the laminars. The results will not only be helpful to reveal the formation mechanism of lunar regolith, but will be directly helpful for tracking sources of regolith materials returned by the Chinese Chang'e-5 sample return mission.