Fischer Meike, Peters Stefan T M, Herwartz Daniel, Hartogh Paul, Di Rocco Tommaso, Pack Andreas
Geowissenschaftliches Zentrum, Abteilung für Geochemie und Isotopengeologie, Georg-August-Universität Göttingen, Göttingen 37077, Germany.
Max-Planck-Institut für Sonnensystemfoschung, Abteilung Planeten und Kometen, Göttingen 37077, Germany.
Proc Natl Acad Sci U S A. 2024 Dec 24;121(52):e2321070121. doi: 10.1073/pnas.2321070121. Epub 2024 Dec 16.
The Moon formed 4.5 Ga ago through a collision between proto-Earth and a planetesimal known as Theia. The compositional similarity of Earth and Moon puts tight limits on the isotopic contrast between Theia and proto-Earth, or it requires intense homogenization of Theia and proto-Earth material during and in the aftermath of the Moon-forming impact, or a combination of both. We conducted precise measurements of oxygen isotope ratios of lunar and terrestrial rocks. The absence of an isotopic difference between the Moon and Earth on the sub-ppm level, as well as the absence of isotope heterogeneity in Earth's upper mantle and the Moon, is discussed in relation to published Moon formation scenarios and the collisional erosion of Theia's silicate mantles prior to colliding with proto-Earth. The data provide valuable insights into the origin of volatiles in the Earth and Moon as they suggest that the water on the Earth may not have been delivered by the late veneer. The study also highlights the scientific value of samples returned by space missions, when compared to analyses of meteorite material, which may have interacted with terrestrial water.
月球形成于45亿年前，是由原始地球与一颗名为忒伊亚的小行星碰撞而成。地球和月球的成分相似性对忒伊亚与原始地球之间的同位素差异施加了严格限制，或者说这需要在月球形成撞击期间及之后，忒伊亚和原始地球物质进行强烈的均质化，或者两者兼而有之。我们对月球和地球岩石的氧同位素比值进行了精确测量。结合已发表的月球形成模型以及忒伊亚硅酸盐地幔在与原始地球碰撞之前的碰撞侵蚀情况，讨论了月球和地球在亚百万分之一水平上不存在同位素差异，以及地球上地幔和月球不存在同位素不均一性的情况。这些数据为地球和月球中挥发性物质的起源提供了有价值的见解，因为它们表明地球上的水可能并非由晚期吸积物带来。与可能与地球水相互作用的陨石物质分析相比，该研究还凸显了太空任务带回样本的科学价值。
