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

Abstract

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.