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).

Layered Structures in the Upper Several Hundred Meters of the Moon Along the Chang'E‐4 Rover's First 1,000‐m Traverse

“…Other layers are thinner, and their source might come from nearby smaller impact events. Our imaging result of the first 500 m along the traverse is consistent with previous studies (e.g., Ding et al., 2022; Li et al., 2020; Zhang et al., 2020). However, we find that the rest 500‐m cross section has a different structure, which has not been reported before.…”

Water Ice Resources on the Shallow Subsurface of Mars: Indications to Rover-Mounted Radar Observation

“…Although Martian-based ground-penetrating radar is set to be deployed on the surface of Mars in 2020, ground-penetrating radar technology was previously deployed on the nearside of the Moon in 2013 (Xiao et al [151], Ding et al [152]). Researchers can adapt from the experience gained through the Moon-based ground-penetrating radar for data processing (Ding et al [152], Su et al [153]), the inversion of the subsurface medium's dielectric property parameters (Feng et al [154], Ding et al [155], Li et al [156]), and the construction of numerical models for the subsurface layers of Mars (Ding et al [157,158]). We believe that with long-term and continuous observation of the Perseverance rover's ground-penetrating radar, as well as advanced data-processing methods and modeling simulations, it is possible to detect the existence of subsurface water ice or liquid water on Mars.…”

Electromagnetic Signal Attenuation Characteristics in the Lunar Regolith Observed by the Lunar Regolith Penetrating Radar (LRPR) Onboard the Chang’E-5 Lander

“…It can be inferred that if the geological age is older, the loss tangent in the lunar regolith is smaller. Meanwhile, an older lunar surface age indicates high selfsimilarity of the materials inside the lunar regolith (Ding et al [54]). It should be noted that in this paper the geological age of the Moon's surface is the age of the local mare unit.…”

“…One possible reason for this is that the older lunar surface age decreases the loss tangent of the lunar regolith. This may not be related to the TiO 2 +FeO content; one possible factor is that the particle size of the lunar regolith grows gradually finer and its interior heterogeneity becomes more aggregated with age (Ding et al [54]). Another possible factor is that the frequency of the Chang'E-5 radar is higher than that of the Chang'E-3 radar; when observing the same medium at a different frequency, the loss tangent measured by the higher frequency radar is likely to be larger than that of the lower-frequency radar.…”