An updated constraint on the local stratigraphy at the Chang’E-4 landing site

Abstract

The Chang'E-4 mission has been exploring the lunar farside. Two scientific targets of the rover onboard are (1) resolving the possible mineralogy related to the South Pole-Aitken basin and (2) understanding the subsurface processes at the lunar farside. Publications to date that are based on the reflectance spectra and radar data obtained by the rover have shown a persistent inconsistency about the local stratigraphy. To explain both the abnormal surface topography at the landing site and the unexpected radargram observed by the rover, the Alder crater has been frequently reported to be older than the mare basalts at that landing site. However, this argument is not supported by earlier geological mapping nor recent crater statistics. Resolving this controversy is critical for a full understanding of the geological history of the landing area and for correct interpretations of the scientific data returned. Employing detailed crater statistics, rigorous statistical analyses, and an updated crater chronology function, this study is determined to resolve the relative ages of the Alder crater, Finsen crater, and the mare basalts on the floor of Von Kármán. Our results reveal that while background secondaries and local resurfacing have widely occurred in the study area, affecting age determinations, the statistics are significant enough to conclude that the Alder crater is the oldest among the three targets. This independent constraint is consistent with both the crosscutting relationships of different terrains in this area and global stratigraphic mapping. Our results exclude Alder as a possible contributor of the post-mare deposits at the landing site, appealing for a more systematic stratigraphy study to resolve the provenances of these deposits.

From Schrödinger to Von Kármán: An Intriguing New Geological Structure Revealed by the Chang'e‐4 Lunar Penetrating Radar

“…Based on the vertical placement of Stratum A and Stratum C, we could constrain the timing of the Schrödinger impact that occurred earlier than the Alder formation event dated to ∼$$3. {5}_{-0.2}^{+0.01}$$ Ga (Lu et al., 2021) or 3.8 Ga (Chang et al., 2021).…”

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

“…The Chinese Chang'E-4 mission landed at the bottom of Von Kármán crater at ∼3.6-3.7 Ga on the far side of the Moon (Chang et al [49], Huang et al [50], Pasckert et al [51]). The observation results from its high-frequency radar show that the material <45 m below the lunar surface are ejecta materials from the Orientale basin (Xiao et al [52]), while the shallow surface layer on the top, which is ∼12 m thick, is fine-grained lunar regolith with a loss tangent constraint of 0.005 ± 0.002 (Li et al [8]), as marked by the red dot in Figure 5.…”

“…According to basalt samples returned by the Apollo and Luna missions, the first peak of volcanic activity on the Moon was between 3.1 Ga and ∼4.3 Ga (Morota et al [60]), while the second peak of volcanic activity was ∼1.8 Ga to 2.5 Ga (Morota et al [60], Haruyama et al [61]). The mare basalt at the Chang'E-4 landing area has an age of ∼3.6-3.7 Ga (Chang et al [49], Huang et al [50], Xiao et al [52]), which probably formed during the period of the first peak of volcanic activity. The geological ages of the Chang'E-3 and Chang'E-5 landing sites are ∼2.5 Ga and 2.0 Ga (Li et al [28], Xiao et al [40]), respectively, and the mare basalt units at these sites probably formed during the second peak of volcanic activity.…”

Deep Learning driven interpretation of Chang'E4 Lunar Penetrating Radar

“…We show new structures previously not considered or imaged, while summarizing or partially reinterpreting the ones already described. (Fortezzo et al, 2020) (~3.0-3.1 Ga (Lu et al, 2021;Chang et al, 2021)) or Late Imbrian (~3.5…”

“…Ga (Gou et al, 2021) or ~3.6 Ga (Ivanov, 2018) ). Further inconsistencies include the significance of the Alder crater (Imbrian (Lu et al, 2021) or Nectarian (Chang et al, 2021)) ejecta in the topmost (> 45 m) layer. While the interpretation of the early (and therefore shorter)…”