Physical and Mechanical Characteristics of Lunar Soil at the Chang'E‐4 Landing Site.

Chang'E‐4, with the Yutu‐2 rover, is the first lunar probe to successfully land and conduct a tour on the far side of the Moon from early 2019. We analyze the physical and mechanical characteristics of lunar soil through the in situ terrain data collected by the panoramic camera onboard the Yutu‐2 rover. With the slip ratio and wheel sinkage obtained by the derived Digital Orthophoto Map (DOM) and Digital Elevation Model (DEM), the mechanical parameters of lunar soil are derived from the slip‐sinkage model. These mechanical parameters and wheel size of the rover are used to obtain the pressure‐sinkage curves, which can estimate the lunar soil strength. The experimental results indicate that the soil strength at the Chang'E‐4 landing site is much higher than that at the Chang'E‐3 landing site. The discrepancies in lunar soil strength between the two landing sites may be related to the local surface topography and degree of space weathering. Plain Language Summary: The knowledge of the physical and mechanical characteristics of lunar soil is of fundamental importance because it is the basis for mineral resource exploration and engineering activity aimed at the construction of lunar bases. The Chang'E‐4 landing site is within the mare floor of the Von Kármán crater inside the South Pole‐Aitken (SPA) basin. The ejecta from the nearby impact craters has covered the Chang'E‐4 landing area. Besides, the lunar soil of the Chang'E‐4 landing area has been relatively mature. Here, a method of analyzing the characteristics of lunar soil is introduced to provide an opportunity to understand the physical and mechanical properties of the mature lunar soil at the Chang'E‐4 landing site. With the terrain data collected by the panoramic camera onboard the Yutu‐2 rover, we can get the relationship curve of the interaction between the rover wheels and lunar soil, such as the pressure‐sinkage curve. The pressure‐sinkage curves can intuitively reflect the discrepancies of lunar soil strength at the Chang'E‐4 and Chang'E‐3 landing sites, which may bear a big relationship to the local surface morphology and degree of space weathering. Key Points: The slip ratio can be estimated by Digital Orthophoto Map and the wheel sinkage can be derived from Digital Elevation ModelThe pressure‐sinkage curves can intuitively reflect the discrepancies of lunar soil strength at different landing sitesThe lunar soil strength at the Chang'E‐4 landing site nearby is higher than that at the Chang'E‐3 landing site [ABSTRACT FROM AUTHOR]