Yutu-2 radar observation of the lunar regolith heterogeneity at the Chang’E-4 landing site

Abstract

Context. The lunar penetrating radar (LPR) carried by the Yutu-2 rover performed the first in situ measurement of the subsurface structure and physical properties of the subsurface materials on the far side of the Moon. It provides an unprecedented opportunity to study the formation and evolution of the lunar surface. Aims. This paper aims to quantitatively estimate the heterogeneity of the lunar regolith using the high-frequency Yutu-2 radar observation and constrain the modeling parameters (e.g., autocorrelation length) on a radar simulation. Methods. The heterogeneity of the lunar regolith was quantified by comparing the simulation and observation acquired by the high-frequency Yutu-2 radar within the first 17 lunar days after its landing. The radar simulation was determined by the numerical calculation of the stochastic regolith model. The change in the autocorrelation length to the modeling was derived by calculating the coarseness of the model. Results. The disturbance range of the lunar regolith with a thickness of ~12 m at the Chang’E-4 landing site is constrained to be ~0.20 ± 0.06 m, indicating a high self-similarity. The stochastic model’s spatial disturbance is controlled by the autocorrelation length and is also scaled by the model size, and the radar scattering echo strength decreases with the increase in autocorrelation length. Conclusions. We conclude that the heterogeneity of lunar regolith is positively related to the geological age. The application of the disturbance range at the decimeter scale might provide a valuable reference to assist in interpreting the radar observation data of the Moon (e.g., Arecibo radar, Min-SAR and Mini-RF, and in situ LPR).