近日，中国科学院地质与地球物理研究所田恒次团队报道了南极-艾特肯盆地形成撞击导致挥发性损失的同位素证据。相关论文于2026年1月12日发表在《美国科学院院刊》杂志上。
近期研究表明，月球背面经历了与正面相似的岩浆洋演化过程。因此，月球正面-背面在火山活动和地壳厚度等方面的差异（即二分性）很可能与南极-艾特肯（SPA）盆地形成时的撞击事件相关。尽管嫦娥六号（CE6）样品中发现的斜长岩碎片可能源自SPA撞击引发的地壳重熔，但此次事件是否（以及如何）修改了月球幔层仍不明确。
研究组首次对CE6低钛玄武岩进行了高精度铁（Fe）和钾（K）同位素测量，结果发现这些玄武岩的δ56Fe（0.13 to 0.21‰）和δ41K（0 to 0.09‰）显著高于阿波罗任务和嫦娥五号（CE5）样品（δ56Fe：0 to 0.11‰；δ41K：0.29 to 0.04‰）。这种重Fe和K同位素特征并非源自宇宙成因效应或撞击体物质的添加。Fe同位素的偏移可通过部分熔融和分异结晶过程解释；而K同位素数据表明，SPA盆地下的幔源区相较于正面幔层具有更重的K同位素组成，这很可能是SPA撞击引发的蒸发作用所致。该研究为月球幔层受撞击改造的显著性提供了确凿证据，并证明大规模撞击事件在形成月球不对称性中可能发挥了关键作用。
附：英文原文
Title: Isotopic evidence for volatile loss driven by South Pole-Aitken basin–forming impact
Author: Tian, Heng-Ci, Zhang, Chi, Li, Wen-Jun, Xue, Dingshuai, Wang, Jing, Yang, Wei, Liu, Yan-Hong, Lin, Yangting, Li, Xian-Hua, Wu, Fu-Yuan
Issue&Volume: 2026-1-12
Abstract: Recent studies suggest that the lunar farside experienced a magma ocean evolution similar to that of the nearside. Thus, the nearside-farside dichotomy, such as volcanism and crustal thickness, is likely related to the South Pole-Aitken (SPA) basin–forming impact. Although the noritic clasts found in Chang’e-6 (CE6) samples may originate from crustal remelting induced by the SPA impact, how (and whether) the lunar mantle was modified by this event remains unclear. Here, we present the first high-precision iron (Fe) and potassium (K) isotopic measurements of CE6 low-Ti basalts, revealing higher δ56Fe (0.13 to 0.21‰) and δ41K (0 to 0.09‰) in these basalts compared to their Apollo and Chang’e-5 (CE5) counterparts (δ56Fe: 0 to 0.11‰; δ41K: 0.29 to 0.04‰). The heavy Fe and K isotopic signatures are unlikely to be derived from cosmogenic effects or the addition of impactor-derived materials. Instead, the heavy Fe isotopes can be explained by partial melting and fractional crystallization processes. For K isotopes, however, the data require that the mantle source beneath the SPA basin had a heavier K isotopic composition than that of the nearside mantle, most likely resulting from evaporation caused by the SPA-forming impact. Our results thus provide robust evidence for significant impact-induced modification of the lunar mantle and demonstrate that large-scale impacts may have played a key role in creating lunar asymmetry.
DOI: 10.1073/pnas.2515408123
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2515408123