Lunar mantle composition and timing of overturn indicated by Mg# and mineralogy distributions across the South Pole-Aitken basin

China's Chang'e‐6 (CE‐6) mission has returned the first‐ever lunar farside samples from a mare plain on the southern Apollo basin floor. The crater statistics of the CE‐6 mare unit and the provenance of the samples are crucial in interpreting the CE‐6 sample analysis results and re‐calibrating the crater chronology function. Here, we conduct a thorough survey of the formation sequence and main source craters of ejecta materials at the sampling area. Our results show that the sampling mare unit has a model age of ∼2.8 Ga and the CE‐6 scooped and drilled samples mainly come from the proximal ejecta of nearby small craters and the local regolith. The total abundance of foreign (non‐mare) materials, primarily from Chaffee S and Vavilov craters, is ∼9.3%. The Chaffee S ejecta may contain lunar upper mantle materials previously excavated by the South Pole‐Aitken impact, which will shed light on the materials of the Moon's interior.

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Composition and Provenance of the Chang′e-6 Lunar Samples: Insights from the Simulation of the Impact Gardening Process

Su,

Xu,

Zhu

et al. 2024

ApJL

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In 2024 June, China’s Chang′e-6 (CE-6) mission successfully returned 1935.3 grams of samples from the lunar farside for the first time. The origin and composition of the unique samples could offer valuable insights into fundamental questions on the Moon’s evolutional history. Besides the local materials of mare basalts, a certain quantity of foreign ejecta materials are expected in the samples, while their percentage was mostly overestimated since the influence of impact gardening was not fully considered. In this study, we model the impact gardening process surrounding the CE-6 landing site by numerical simulations. Our simulations show that impact gardening played a key role in overturning the local materials and diluting the foreign ones in the top-meters-deep layer at the landing site. About 90% of the CE-6 drilled samples, which were sampled within the top ∼1 m deep layer, are predicted to be the local intermediate-Ti mare basalts originating in the deeper area of 1–60 m, and the underlying low-Ti basalts may make up <1%. The foreign materials in the CE-6 drilled samples likely constitute a minor portion, with an abundance of ∼3.0%. As the primary contributor (∼2.1%) of foreign materials, Chaffee S ejecta may contain lunar mantle materials excavated by the South Pole–Aitken basin.

show abstract

Lunar mantle composition and timing of overturn indicated by Mg# and mineralogy distributions across the South Pole-Aitken basin

Cited by 3 publications

References 40 publications

Composition, structure, and origin of the Moon

Composition, structure, and origin of the Moon

Chronology, Local Stratigraphy, and Foreign Ejecta Materials at the Chang'e‐6 Landing Site: Constraints on the Provenance of Samples Returned From the Moon's Farside

Composition and Provenance of the Chang′e-6 Lunar Samples: Insights from the Simulation of the Impact Gardening Process

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