The Composition and Stratigraphy of the Chang’e-6 Landing Mare

Abstract China’s Chang’e-6 (CE-6) mission returned lunar samples from the southern mare in the Apollo basin formed in the prominent South Pole–Aitken basin. The basic geological context of the landing mare has been well resolved. Separated by a north–south extending high-standing wrinkle ridge, the western and eastern parts of the southern mare have different compositions and model ages of emplacement. However, the stratigraphic context of the landing mare, especially the eruption sequence of the basaltic deposits, is marginally constrained due to the prolonged regional geological history and prominent mixing by exotic ejecta. This shortage of knowledge could be a challenge in sample investigations. In this work, we investigated the reflectance spectra for fresh materials of young craters to analyze the composition and stratigraphy of the landing mare. We verified that the western mare where CE-6 landed is composed of at least two layers of basaltic deposits. The surface basaltic deposits have a higher content of TiO 2 (∼3.7 wt%) than the underlying lower basaltic deposits (∼2.3 wt% TiO 2 ), which share similar compositions with the eastern mare. Potential flow fronts of basaltic flows that originated from the west are observed on top of the wrinkle ridge, and they have similar compositions to the eastern mare. These new lines of evidence support that the basaltic deposits in the eastern mare existed beneath the western mare, suggesting that the eruption was located within the western mare. The regional stratigraphic context is helpful for ongoing sample analyses.