Characterization of lobate scarps at the western rim of the Apollo basin using high-resolution DEMs generated using generative adversarial network (GAN) based approach

Abstract

Chang'e-6 is the first sample-return mission from the lunar farside and has returned samples from the landing site within the Apollo basin on June 25, 2024. Lobate scarps have been identified approximately 300 km northwest of the Chang'e-6 landing site (and at western rim of the Apollo basin). The distribution and morphological characteristics of lobate scarps are crucial for understanding the lunar geological history of the landing area. In this research, we have analyzed the spatial distribution and formation age of lobate scarps at western rim of the Apollo basin. The morphology, dynamical models, and formation ages of lobate scarps are investigated through Mohr-Coulomb measurement and crater size-frequency distribution measurements (CSFD). We generated high-resolution digital elevation models by deep learning method using Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) imagery and Selenological and Engineering Explorer (SELENE) and Lunar Orbiter Laser Altimeter (LOLA) Digital Elevation Model (SLDEM), which enabled the study of lobate scarps in areas lacking NAC DTM coverage, and their accuracy were thoroughly validated. The displacement-length ratios of the lobate scarps are calculated, with an average of approximately 3.80 %. By calculating the morphological parameters of lobate scarps, inferring their formation ages, and studying their spatial distribution, we find that these lobate scarps are distributed in the highlands nearby the Apollo basin edge. They were formed under horizontal compressive stresses exceeding 400 MPa during the last 80 Ma, which is consistent with the initially totally molten (ITM) model. This finding is further supported by cross-validation with the ²³⁸U/²⁰⁴Pb ratios from lunar far-side samples by the Chang'e-6 mission, challenging the notion that the lunar magma ocean (LMO) can prolong magmatic activity through KREEP.