Copernican‐Aged (<200 Ma) Impact Ejecta at the Chang'e‐5 Landing Site: Statistical Evidence From Crater Morphology, Morphometry, and Degradation Models. Issue 20 (19th October 2021) - Qian, Yuqi
Abstract: Chang'e‐5 successfully returned ∼1, 731 g of lunar samples on December 17, 2020. We systematically studied the morphology and morphometry of craters surrounding the Chang'e‐5 site based on high‐resolution images. A key ejecta source crater database was produced, incorporating their morphometrical parameters, excavation depth, target rock types, and ages from either crater counting, crater morphology or degradation methods. We found that (a) the regolith at the Chang'e‐5 site is ∼4–6 m thick, (b) ejecta are primarily from five proximal craters, including Xu Guangqi, dominantly with ages <200 Ma; (c) distal materials are mainly from Harpalus, Copernicus, Aristarchus, and Mairan G craters; (d) the drill samples are likely to be mainly from Impact Crater (IC)‐261 and IC‐265 particles at the top and the contribution of Xu Guangqi increases with depth; (e) the ejecta of Xu Guangqi would buried preexisting materials but probably overturned by postimpacts. Plain Language Summary: The Chang'e‐5 mission, China's first lunar sample‐return mission, successfully landed on the Moon on December 1, 2020, at 43.06°N, 51.92°W, and returned 1, 731 g of lunar soil samples. Because of the potentially large contribution from local impact craters to the collected samples, we conducted this research to study these craters based on high‐resolution orbital data. Our results support the hypothesis that local craters are the major ejecta sources, mainly from Impact Crater (IC)‐259, IC‐261, IC‐265, IC‐266, and Xu Guangqi crater. Of these, Xu Guangqi is the most critical ejecta source crater and Chang'e‐5 landed on its ejecta deposit. Its ejecta would bury preexisting materials, such as those from distant craters Harpalus, Copernicus, Aristarchus, and Mairan G, but subsequent craters may redistribute buried materials again, and represented in the regolith sampled by Chang'e‐5. Key Points: An impact crater database surrounding the Chang'e‐5 site was produced Crater ages are constrained either by CSFD or crater morphology or degradation methods Ejecta are mainly from local craters, delivered by Copernican‐aged (>200 Ma) craters