On the provenance of the Chang’E-5 lunar samples

1Bojun Jia,1,2,3Wenzhe Fa,1Mingwei Zhang,4Kaichang Di,5Minggang Xie,1Yushan Tai,7,3Yang Li
Earth and Planetary Science Letters 596, 117791 Link to Article [https://doi.org/10.1016/j.epsl.2022.117791]
1Institute of Remote Sensing and Geographical Information System, School of Earth and Space Sciences, Peking University, Beijing, China
2State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
3Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei, China
4State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences, China, Beijing, China
5College of Science, Guilin University of Technology, Guilin, China
6Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
Copyright Elsevier

China’s Chang’E-5 (CE-5) mission has collected 1.731 kg samples from a young mare basalt unit (named P58/EM4) in the northeastern Oceanus Procellarum region of the Moon. Accurate tracing of the provenance of returned samples is essential for understanding their laboratory measurements, which can provide critical information about the Moon and the inner Solar System. In this article, the provenance, chemical composition, formation, and evolution processes of the regolith at the CE-5 landing site are analyzed by using remote sensing observations and crater ejecta deposition models. A comprehensive search based on crater ejecta thickness model shows that 1892 impact craters in P58 likely deposited ∼0.56 m of primary ejecta at the landing site, whereas 4 impact craters outside P58 deposited 0.05 m of distal ejecta that further excavated and reworked ∼0.5 m thick local mare basalt. Twelve craters within 1 km from the CE-5 landing site are estimated to contribute ∼0.49 m (~88%) of the ejecta materials, and their ejecta source regions are investigated using the Maxwell Z model. Among these 12 craters, Xu Guangqi and a smaller crater near the landing site are the two most volumetrically significant contributors (~0.3 m and ∼0.12 m). Craters more than 1 km distant from the landing site deposited fewer exotic materials, but some of them could have delivered low-Ti materials to the sampling site. Finally, the regolith stratigraphy at the landing site is investigated based on the identified and assumed impact sequence by using a Monte Carlo-based ejecta ballistic sedimentation model. The results reveal a depth-varying FeO/TiO2 abundance profile at the landing site, suggesting that the sedimentation of distant ejecta can reduce FeO/TiO2 abundance of the underlying layer by ∼1 wt.% at ∼0.5 m depth. Our results provide key information on sample provenance and regolith stratigraphy of the landing site, which is crucial to deciphering the returned CE-5 samples.


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