Layering Structures in the Porous Material Beneath the Chang'e‐3 Landing Site

The lunar penetrating radar (LPR) onboard the Chinese Chang'e‐3 (CE‐3) mission obtained high‐resolution profile data for the continuous ejecta deposits of the Ziwei crater. Geological background suggests that the continuous ejecta deposits contain few large boulders, and the ejecta deposits were largely originated from the pre‐impact regolith. Using the top ~50 ns of radar data, we estimate the bulk density and porosity for the ejecta deposits based on hyperbolic echo patterns in the radargram that are caused by subsurface boulders. The physical properties are close to those of typical lunar regolith. Numerous subparallel and discontinuous short layers are visible in the radargram of the continuous ejecta deposits. The dielectric coefficients of the layering structures are estimated, and their permittivity is slightly larger than that of typical lunar regolith and less than that of basaltic rocks. Cratering physics together with the geological context of this area suggest that the layering structures are most likely ground gravels and/or melt‐welded breccias that were sheared due to the horizontal momentum of the impact ejecta. This interpretation is indicative of the origin of the enigmatic layering structures in regolith core samples returned by the Apollo and Luna missions. The results also highlight the importance of ejecta emplacement in shaping the structure of lunar regolith. Plain Language Summary Large discrepancies existed in previous geological interpretations using the Chang'e‐3 high‐frequency LPR data. A comprehensive review of previous studies that used the Chang'e‐3 radar data noticed that most previous studies agree that the top ~50 ns of the radargram is restricted within the continuous ejecta deposits of the Ziwei crater. Analyses for the stratigraphy of the landing site suggested that the continuous ejecta deposits were largely composed by pre‐impact regolith. Using the high‐frequency LPR data, we reconstructed the depth profiles of physical parameters (i.e., relative permittivity, bulk density, and porosity) for the continuous ejecta deposits of the Ziwei crater, which are similar with those of typical lunar regolith. Many subparallel and discontinuous layers are observed in the radargram, which were not deciphered before. We carried out numerical simulations to study the nature of the layering features. Results suggest that these structures have a permittivity slightly larger than that of typical lunar regolith. Geological context of t