Fig. 3: Distribution of Apollo and Chang’E Missions Landing Sites and Physical Property Inversion of Lunar Regolith Parameters.

a Distribution of Apollo and Chang’E mission landing sites on the Moon. The base map is a global lunar DEM observed by CE-1 (Image ID: CE1_GRAS_DEM_500m_001_GLOBAL_A). The landing sites of CE-3 to CE-6 missions are marked with stars, while the landing sites of Apollo missions are labelled with triangles. b The relationship between the loss tangent derived from radar inversions and Apollo 12 to Apollo 17 sample tests versus the geological age of the lunar surface. This plot shows the normalized loss tangent, FeO+TiO₂ mass fraction, and the corresponding geological ages. The loss tangent has been normalized using Eq. (1) to remove the effect of different bulk densities. The stars represent regolith parameters obtained from in-situ radar observations during the Chang’E missions, the cross is the Apollo 17 mission in-situ radar measurements, and the triangles denote the measurements from Apollo regolith samples. The colors of the symbols represent different geological ages, with red, green, and blue and indicate young, medium, and old geological ages, respectively. c Fitted results of loss tangent values versus the age of the landing site based on radar observations from CE-3, CE-4, CE-5, and CE-6. In this plot, the radar-derived results from the Chang’E missions are shown in stars, while the red line is the fitted relationship. Additionally, Apollo regolith sample measurements and in-situ measurement presented in panel (b) are included, represented by triangles and a cross, respectively.