2025-03-21 中国科学院（CAS）
Schematic illustrating that Chang’e-6 norites document the 4.25 Ga lunar South Pole-Aitken impact event (Image by SU Bin)
＜関連情報＞
- https://english.cas.cn/newsroom/research_news/earth/202503/t20250321_908490.shtml
- https://academic.oup.com/nsr/advance-article/doi/10.1093/nsr/nwaf103/8088430
嫦娥6号のサンプルによって明らかになった42億5000万年前の南極・エイトケン大衝突 South Pole–Aitken massive impact 4.25 billion years ago revealed by Chang’e-6 samples
Bin Su, Yi Chen, Zeling Wang, Di Zhang, Haojie Chen, Sheng Gou, Zongyu Yue, Yanhong Liu, Jiangyan Yuan, Guoqiang Tang …
National Science Review Published:20 March 2025
DOI:https://doi.org/10.1093/nsr/nwaf103
Abstract
As the largest and oldest well-preserved impact structure on the Moon, the South Pole–Aitken (SPA) basin on the lunar farside is critical for understanding early Solar System dynamics and lunar history, but accurately determining its age remains challenging. Crater-counting chronology and Apollo sample studies propose various SPA-forming ages, which require validation by in-situ sampling of the SPA basin. Here we present the petrology, geochemistry, and chronology of norite clasts from the SPA basin returned by Chang’e-6. These norites have highly anorthite-rich, rare-earth element (REE)-poor plagioclase and magnesium-rich pyroxene, in contrast with Mg-suite norites returned from the lunar nearside. Abundant Fe-Ni metals with meteoritic Ni/Co ratios, depletion of volatile elements, and variable grain sizes and cooling rates strongly indicate that the norites were crystallised from an impact melt sheet. Precise Pb–Pb ages of zirconium-bearing minerals in the norites yield two distinct impact events at 3.87 Ga and 4.25 Ga. The former represents an impact resetting event within the basin. The latter finding is most consistent with the age of the SPA impact, providing an initial 4.25 Ga anchor for the older end of the lunar crater chronology and refining the timeline for early lunar evolution.
