The Earth-Moon system likely formed as a result of a collision between two large planetary objects. Debate about their relative masses, the impact energy involved, and the extent of isotopic homogenization continues. We present the results of a high-precision oxygen isotope study of an extensive suite of lunar and terrestrial samples. We demonstrate that lunar rocks and terrestrial basalts show a 3 to 4 ppm (parts per million), statistically resolvable, difference in Δ¹⁷O. Taking aubrite meteorites as a candidate impactor material, we show that the giant impact scenario involved nearly complete mixing between the target and impactor. Alternatively, the degree of similarity between the Δ¹⁷O values of the impactor and the proto-Earth must have been significantly closer than that between Earth and aubrites. If the Earth-Moon system evolved from an initially highly vaporized and isotopically homogenized state, as indicated by recent dynamical models, then the terrestrial basalt-lunar oxygen isotope difference detected by our study may be a reflection of post-giant impact additions to Earth. On the basis of this assumption, our data indicate that post-giant impact additions to Earth could have contributed between 5 and 30% of Earth's water, depending on global water estimates. Consequently, our data indicate that the bulk of Earth's water was accreted before the giant impact and not later, as often proposed.

中文翻译：

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氧同位素证据表明在形成高能月球的巨大撞击之前会积聚地球的水。

地球月球系统很可能是两个大型行星物体之间碰撞的结果。关于它们的相对质量，所涉及的冲击能量以及同位素均质化程度的争论仍在继续。我们介绍了一套广泛的月球和陆地样品的高精度氧同位素研究的结果。我们表明，月球岩石和地球玄武岩显示出3〜4 ppm（百万分之一），统计学解析，在Δ差¹⁷ O.以顽火无球陨石陨石作为候选冲击材料，我们表明，巨型撞击情景参与之间几乎完全混合目标和影响者。或者，相似的Δ之间的相似度¹⁷撞击者和原始地球的O值必须比地球与仿生石之间的O值更接近。如最近的动力学模型所示，如果地球-月亮系统从最初的高度汽化和同位素均质状态演化而来，那么我们的研究发现的陆地玄武岩-月球氧同位素差异可能反映了对地球的巨大撞击后的增加。基于此假设，我们的数据表明，根据全球水资源估算，对地球的巨大影响可能贡献了地球水资源的5％至30％。因此，我们的数据表明，地球的大部分水是在大撞击发生之前而不是通常提出的之后增加的。