近日，美国哈佛大学Drabon Nadja和Knoll Andrew H.教授合作，报道了巨大陨石撞击对古太古代地表环境和生命的影响。相关论文于2024年10月21日发表在《美国科学院院刊》杂志上。

据介绍，大型陨石撞击强烈地影响了早期地球的可居住性。太古代的岩石记录了至少16次重大撞击事件，涉及直径大于10km的火流星。这些影响可能对地表环境造成了严重的（尽管是暂时的）后果。然而，它们对早期生活的影响尚不清楚。

研究人员分析了贯穿S2撞击事件（37至58km碳质球粒陨石）沉积岩的沉积学、岩相学和碳同位素地球化学结果，以评估其环境影响和生物后果，该事件沉积构成了南非3.26Ga的Fig Tree群中一部分。结果显示，撞击引发了1)一场巨大的海啸，将富Fe²⁺的深水混合到贫Fe²⁺的浅水中，并将碎片冲入沿海地区；2)加热导致了海洋表面海水的部分蒸发，并可能在短期内增加陆地的风化和侵蚀，以及3)从S2火流星的蒸发中注入P。

S2撞击事件正上方地层含有丰富的菱铁矿，这些菱铁矿与有机质共生，δ¹³C_carb值较轻且变化较大。这与撞击事件后微生物的铁循环是一致的。因此，S2撞击可能会对生命产生区域性的积极和消极的影响，如果不是全球性的的话。海啸、大气加热和黑暗可能会大量杀死浅水层中的光养微生物。然而，生物圈可能迅速恢复，并且从中期来看，营养物质和铁的增加可能促进微生物繁殖，特别是铁循环微生物。

附：英文原文

Title: Effect of a giant meteorite impact on Paleoarchean surface environments and life

Author: Drabon, Nadja, Knoll, Andrew H., Lowe, Donald R., Bernasconi, Stefano M., Brenner, Alec R., Mucciarone, David A.

Issue&Volume: 2024-10-21

Abstract: Large meteorite impacts must have strongly affected the habitability of the early Earth. Rocks of the Archean Eon record at least 16 major impact events, involving bolides larger than 10 km in diameter. These impacts probably had severe, albeit temporary, consequences for surface environments. However, their effect on early life is not well understood. Here, we analyze the sedimentology, petrography, and carbon isotope geochemistry of sedimentary rocks across the S2 impact event (37 to 58 km carbonaceous chondrite) forming part of the 3.26 Ga Fig Tree Group, South Africa, to evaluate its environmental effects and biological consequences. The impact initiated 1) a giant tsunami that mixed Fe²⁺-rich deep waters into the Fe²⁺-poor shallow waters and washed debris into coastal areas, 2) heating that caused partial evaporation of surface ocean waters and likely a short-term increase in weathering and erosion on land, and 3) injection of P from vaporization of the S2 bolide. Strata immediately above the S2 impact event contain abundant siderites, which are associated with organic matter and exhibit light and variable δ¹³C_carbb values. This is consistent with microbial iron cycling in the wake of the impact event. Thus, the S2 impact likely had regional, if not global, positive and negative effects on life. The tsunami, atmospheric heating, and darkness would likely have decimated phototrophic microbes in the shallow water column. However, the biosphere likely recovered rapidly, and, in the medium term, the increase in nutrients and iron likely facilitated microbial blooms, especially of iron-cycling microbes.

DOI: 10.1073/pnas.2408721121

Source: https://www.pnas.org/doi/abs/10.1073/pnas.2408721121