Dielectric Properties of Lunar Materials at the Chang’e-4 Landing Site

Abstract

On January 3rd 2019, the Chang’e-4 mission successfully landed in the Von Kármán Crater inside the South Pole-Aitken (SPA) basin and achieved the first soft landing on the farside of the Moon. Lunar penetrating radar (LPR) equipped on the rover measured the shallow subsurface structure along the motion path for more than 700 m. LPR data could be used to obtain the dielectric properties of the materials beneath the exploration area, providing important clues as to the composition and source of the materials. Although the properties of the upper fine-grained regolith have been studied using various methods, the underlying coarse-grained materials still lack investigation. Therefore, this paper intends to estimate the loss tangent of the coarse-grained materials at depth ranges of ~12 and ~28 m. Stochastic media models with different rock distributions for the LPR finite-difference time-domain (FDTD) simulation are built to evaluate the feasibility of the estimation method. Our results show that the average loss tangent value of coarse-grained materials is 0.0104±0.0027, and the abundance of FeOT+TiO2 is 20.08 wt.%, which is much higher than the overlying fine-grained regolith, indicating different sources.

Heterogeneous Weathering Process of Lunar Regolith Revealed by Polarimetric Attributes Analysis of Chang’E‐4 Lunar Penetrating Radar Data Acquired During the Yutu‐2 Turnings

“…Regions 12 and 13 are two separated areas of concentrated rocks; different strengths of surface‐like scatterings indicate smaller rock sizes and higher regolith maturity in region 13. Besides, region 14 has been interpreted as a buried crater with large quantities of rocks (Lai, Cui, et al., 2021; Zhang, Xu et al., 2021; Zhou, Feng, Ding, et al., 2021), presenting the minimum of regolith maturity along the Yutu‐2 route. The regolith below 12 m depth also shows horizontal heterogeneity.…”

“…In other studies, the LPR data are applied to the analysis of subsurface properties and rock quantity in the regolith (Dong et al., 2020; Lai et al., 2021a, 2021b; Zhang, Xu et al., 2021; Zhou, Feng, Ding, et al., 2021). However, the rock localization using LPR data mainly depends on the reflection signals from the subsurface and the results in previous works cannot determine whether these signals are from horizontally distributed rocks or continuous geological interfaces (Zhou, Feng, Ding, et al., 2021) because the regolith maturity over the full depth has not been obtained.…”

Magnetic field coupling with lunar soil simulants

“…Table 2 also includes reported constitutive parameter values for other particulate samples, including experimental measurements for actual lunar regolith and simulants at various frequencies between 1 MHz and 30 GHz 17,[29][30][31][32][33][34][35][36] . Figure 6 shows a plot of the estimated attenuation constant, α (Np/m), for the reported samples.…”

Study on the Influencing Factors of the Permittivity Estimation Method Considering Antenna Layout Based on Lunar Penetrating Radar

“…As demonstrated in Figure 3, when there is a reflector in the regolith, a hyperbola is formed on the radargram (the red curve). The hyperbola can be detected on the radargram (Wang et al 2021;Fa et al 2015;Fa 2020;Lai et al 2021), and the coordinates of the points on the hyperbola can be obtained. Hence, combined with Equation (2), the permittivity can be obtained by the curve fitting method (Feng et al 2017;Ding et al 2020Ding et al , 2021Wang et al 2021).…”