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Oxygen isotopic evidence for accretion of Earth's water before a high-energy Moon-forming giant impact

Greenwood, Richard C.; Barrat, Jean-Alix; Miller, Martin F.; Anand, Mahesh; Dauphas, Nicolas; Franchi, Ian A.; Sillard, Patrick and Starkey, Natalie A. (2018). Oxygen isotopic evidence for accretion of Earth's water before a high-energy Moon-forming giant impact. Science Advances, 4(3), article no. eaao5928.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1126/sciadv.aao5928
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Abstract

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.

Item Type: Journal Item
Copyright Holders: 2018 The Authors
ISSN: 2375-2548
Project Funding Details:
Funded Project NameProject IDFunding Body
Consolidated GrantST/10001964/1STFC
Consolidated GrantST/L000776/1STFC
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Related URLs:
Item ID: 54309
Depositing User: Richard Greenwood
Date Deposited: 13 Apr 2018 10:33
Last Modified: 23 Oct 2019 16:24
URI: http://oro.open.ac.uk/id/eprint/54309
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