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

Abstract

AbstractThe 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.