High-Precision Imaging and TiO2 + FeO Content Estimation of Lunar Farside Subsurface Layers: Insights From Chang'e-4 Lunar Penetrating Radar Data

The Chang'e-4 Lunar Penetrating Radar (LPR) has proven instrumental in uncovering the structure and composition of the Von Kármán crater on the lunar farside. Utilizing high-frequency (HF) LPR data collected during the first 53 lunar days, this study employs Least Squares Migration to achieve high-resolution imaging of shallow subsurface structures. Additionally, the peak frequency shift method is applied to estimate the loss tangent and the TiO₂ + FeO content of the shallow regolith. The average loss tangent of the shallow regolith ranges from 4.3 × 10⁻³ to 5.5 × 10⁻³, corresponding to an iron-titanium content of 11.2 wt% to 14.7 wt%. Along the Yutu-2 rover's traverse (300–500 m and 1,000–1,150 m), the regolith exhibits high TiO₂ + FeO content, suggesting that these materials may originate from deeper basalt layers. By integrating radar profiles with estimates of TiO₂ + FeO content, this study provides a detailed geological interpretation of subsurface layers and unique structures. These findings reconstruct critical geological events in the shallow subsurface at the landing site, offering new insights into the geological evolution of this region.