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

Abstract

We revealed the layered structure of the upper three hundred meters of the lunar surface in the South Pole‐Aitken Basin by using the measurements from the Lunar Penetrating Radar (LPR) onboard the Chang’E‐4 rover. The result shows that five large strata are identified by the LPR 60‐MHz channel below the depth of 90 m, with thicknesses ranging from 20 m to larger than 70 m. We speculate that at least three strata are basalt flows, while the shallowest stratum is composed of multiple thin lava flows. The thickness of the strata decreases with the decreasing depth, suggesting a progressively smaller lava effusion rate over time. To evaluate the reliability of the result, a comparison was made between Chang'E‐4, Chang'E‐3, and ground test low‐frequency data. The LPR 500‐MHz channel unveiled the structure of weathered material in the top ∼40 m, revealing several layers as well as a buried paleo crater and its ejecta blanket in the regolith.

Yutu-2 Radar Observations at the Chang’E-4 Landing Site: The Shallow Geological Structure and Its Dielectric Properties

“…In the interpretation of low-frequency radar observations, different researchers have made various divisions from different aspects [32,37,46,48]. For the rough division explanation, we will mainly use the division pattern of Feng et al [49]. For a more visual and detailed look at the division, it is shown in the division graph (Figure 3) of Feng et al [49].…”

“…For the rough division explanation, we will mainly use the division pattern of Feng et al [49]. For a more visual and detailed look at the division, it is shown in the division graph (Figure 3) of Feng et al [49]. Zhang et al [37] divided the 450 m below the lunar surface into three layers:…”

Deep Learning driven interpretation of Chang'E4 Lunar Penetrating Radar

“…Up to now, most of the studies used visual interpretation to detect horizons by only considering the reflection amplitude, while just in two cases, single and straightforward signal attributes such as the instantaneous amplitude and signal central frequency (Feng et al, 2023) were exploited. In this way, an unavoidable subjectivity was introduced into the interpretation process, and other analyses were additionally needed to support the interpretation, in particular numerical simulation and velocity analysis (Giannakis et al, 2021;Wang et al, 2021;Li et al, 2022;Chen et al, 2022).…”

“…Other studies estimated the dielectric constant from the reflection amplitude (e.g. Dong et al, 2020;Feng et al, 2023). This inversion approach is undoubtedly effective in some cases (Forte et al, 2014).…”