Joy K H, Wang N, Snape J F, Goodwin A, Pernet-Fisher J F, Whitehouse M J, Liu Y, Lin Y T, Darling J R, Tar P, Tartèse R
Department of Earth and Environmental Sciences, The University of Manchester, Manchester, UK.
Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China.
Nat Astron. 2025;9(1):55-65. doi: 10.1038/s41550-024-02380-y. Epub 2024 Oct 16.
The Moon's farside South Pole-Aitken (SPA) basin is the largest and oldest visible impact basin in the inner Solar System. Determining the timing of this catastrophic event is key to understanding the onset of the lunar basin-forming epoch, with implications for understanding the impact bombardment history of the inner Solar System. Despite this, the formation age of the SPA basin remains poorly constrained. Here we show that the chemical composition of the lunar meteorite Northwest Africa 2995 is in good agreement with lithologies exposed within the southern region of the SPA basin. Radiometric dating of a range of mineral and rock components in Northwest Africa 2995 yielded consistent dates of ~4.32-4.33 billion years old. We interpret these dates as the age of SPA basin formation, inferring that this event occurred ~120 million years before the formation of the main cluster of lunar impact basins between ~4.2 Ga and 3.8 Ga. This weakens support for a narrow period of lunar late heavy impact bombardment and also implies that the earliest formed impact basins on the Moon (that is, >4.33-4.5 Ga old) were erased either by the SPA impact itself when its formation caused massive resurfacing of the lunar surface or through other geological processes.
月球背面的南极-艾特肯（SPA）盆地是内太阳系中最大且最古老的可见撞击盆地。确定这一灾难性事件的发生时间对于理解月球盆地形成时期的起始至关重要，这对于了解内太阳系的撞击轰击历史也具有重要意义。尽管如此，SPA盆地的形成年龄仍然受到很大限制。在此我们表明，月球陨石西北非洲2995的化学成分与SPA盆地南部区域暴露的岩性非常吻合。对西北非洲2995中一系列矿物和岩石成分的放射性测年得出了一致的年龄，约为43.2 - 43.3亿年。我们将这些年龄解释为SPA盆地的形成年龄，推断该事件发生在约42亿年至38亿年之间月球主要撞击盆地群形成之前约1.2亿年。这削弱了对月球晚期重轰击狭窄时期的支持，并且还意味着月球上最早形成的撞击盆地（即年龄大于43.3 - 45亿年）要么在SPA撞击形成时导致月球表面大规模重铺时被该撞击本身抹去，要么是通过其他地质过程被抹去。
