Oxygen isotopic evidence for accretion of Earth’s water before a high-energy Moon-forming giant impact - Université de Bretagne Occidentale Access content directly
Journal Articles Science Advances Year : 2018

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

Jean-Alix J-A Barrat
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Martin Miller
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Nicolas Dauphas
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Ian Franchi
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Patrick Sillard
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Natalie Starkey
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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 D 17 O. 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 D 17 O 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.
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hal-01901935 , version 1 (08-01-2021)

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Attribution - NonCommercial

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Richard Greenwood, Jean-Alix J-A Barrat, Martin Miller, Mahesh Anand, Nicolas Dauphas, et al.. Oxygen isotopic evidence for accretion of Earth’s water before a high-energy Moon-forming giant impact. Science Advances , 2018, 4 (3), ⟨10.1126/sciadv.aao5928⟩. ⟨hal-01901935⟩
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