Mare Basalt Thickness in the Chang'E-6 Landing Region: Insights Into Late-Stage Volcanism in the Lunar Farside South Pole–Aitken Basin

Abstract

Chang'E-6 probe collected lunar samples from a young mare plain in the southern Apollo basin within the South Pole–Aitken (SPA) basin on the lunar farside. By synthesizing morphological, compositional, and spectral data, we analyzed the excavation depths of craters that penetrated different basalt layers to evaluate the stratigraphy and total thickness of the mare deposits using multiple remote sensing data sets (Kaguya Multiband Imager). Results reveal that the upper Eratosthenian-aged basalt layer, approximately 79 m thick, is relatively thick in the west and gradually thins toward the east but thickens again, while the lower Imbrian-aged mare layer, around 44 m thick, exhibits an overall thinning trend from northwest to southeast. This thickness variation of the Eratosthenian-aged basalt unit is likely influenced by the formation of the nearby wrinkle ridge (∼3.2 Ga), which resulted from the cooling and contraction of the Imbrian-aged basalt unit. The ridge may have acted as a barrier, obstructing the westward flow of moderate-Ti lava that later formed the Eratosthenian-aged basalts. Both Chang'E-5 and Chang'E-6 landing regions show similarities in basalt composition and thickness; however, the Chang'E-6 zone experienced significantly smaller eruption volumes. The similar eruptive volumes between Imbrian- and Eratosthenian-aged basalts at the Chang'E-6 landing region suggest that late-stage mare volcanism in the SPA basin was likely controlled by a thin crust facilitating magma ascent and dike propagation rather than a gradual increase in eruption volume over time.