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） 盆地是太阳系内最大、最古老的可见撞击盆地。确定这一灾难性事件的时间是理解月球盆地形成时代开始的关键，对理解太阳系内部的撞击轰炸历史具有重要意义。尽管如此，SPA 盆地的形成年龄仍然受到较差的限制。在这里，我们表明 2995 年非洲西北陨石的化学成分与 SPA 盆地南部地区暴露的岩性非常一致。2995 年对西北非洲的一系列矿物和岩石成分进行辐射测年得出的一致年代为 ~4.32-43.3 亿年。我们将这些日期解释为 SPA 盆地形成的年龄，推断这一事件发生在 ~4.2 Ga 和 3.8 Ga 之间的月球撞击盆地主集群形成前 ~1.2 亿年。这削弱了对月球晚期重撞击轰击的狭窄时期的支持，也意味着月球上最早形成的撞击盆地（即 >4.33–4.5 Ga 旧）要么被 SPA 撞击本身抹去，要么被其形成导致月球表面的大规模重新浮出水面，要么被其他地质过程抹去。