title: Identification of the giant impactor Theia in lunar rocks.
abstract: The Moon was probably formed by a catastrophic collision of the proto-Earth with a planetesimal named Theia. Most numerical models of this collision imply a higher portion of Theia in the Moon than in Earth. Because of the isotope heterogeneity among solar system bodies, the isotopic composition of Earth and the Moon should thus be distinct. So far, however, all attempts to identify the isotopic component of Theia in lunar rocks have failed. Our triple oxygen isotope data reveal a 12 ± 3 parts per million difference in Δ(17)O between Earth and the Moon, which supports the giant impact hypothesis of Moon formation. We also show that enstatite chondrites and Earth have different Δ(17)O values, and we speculate on an enstatite chondrite-like composition of Theia. The observed small compositional difference could alternatively be explained by a carbonaceous chondrite-dominated late veneer.
authors.affiliation: Georg-August-Universität Göttingen, Geowissenschaftliches Zentrum, Abteilung Isotopengeologie, Goldschmidtstraße 1, 37073 Göttingen, Germany. Universität zu Köln, Institut für Geologie und Mineralogie, Zülpicher Straße 49a, 50674 Köln, Germany. d.herwartz@uni-koeln.de.
authors.forename: Daniel
authors.initials: D
authors.lastname: Herwartz
authors.affiliation: Georg-August-Universität Göttingen, Geowissenschaftliches Zentrum, Abteilung Isotopengeologie, Goldschmidtstraße 1, 37073 Göttingen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Pack
authors.affiliation: Georg-August-Universität Göttingen, Geowissenschaftliches Zentrum, Abteilung Isotopengeologie, Goldschmidtstraße 1, 37073 Göttingen, Germany.
authors.forename: Bjarne
authors.initials: B
authors.lastname: Friedrichs
authors.affiliation: Westfälische Wilhelms-Universität Münster, Institut für Planetologie, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany.
authors.forename: Addi
authors.initials: A
authors.lastname: Bischoff