^1,2Timo Hopp,^1,3Nicolas Dauphas,³Maud Boyet,⁴Seth A. Jacobson,⁵Thorsten Kleine
Science 390, 819-823 Link to Article [DOI: 10.1126/science.ado062]
¹Department of the Geophysical Sciences, The University of Chicago, Chicago, IL, USA
Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany
²Department of Earth and Planetary Sciences, The University of Hong Kong, Hong Kong, China
³Laboratoire Magmas et Volcans, Université Clermont Auvergne, Centre National de la Recherche Scientifique, Institut de Recherche pour le Développement, Observatoire de Physique du Globe de Clermont-Ferrand, Clermont-Ferrand, France
⁴Department of Earth and Environmental Sciences, Michigan State University, East Lansing, MI, USA
⁵Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany
Reprinted with permission from AAAS

The Moon formed from a giant impact of a planetary body, called Theia, with proto-Earth. It is unknown whether Theia formed in the inner or outer Solar System. We measured iron isotopes in lunar samples, terrestrial rocks, and meteorites representing the isotopic reservoirs from which Theia and proto-Earth might have formed. Earth and the Moon have indistinguishable mass-independent iron isotopic compositions; both define one end of the range measured in meteorites. Combining our results with those for other elements, we performed mass balance calculations for Theia and proto-Earth. We found that all of Theia and most of Earth’s other constituent materials originated from the inner Solar System. Our calculations suggest that Theia might have formed closer to the Sun than Earth did.

^1,2Ke Zhu,³Akira Yamaguchi,⁴Paolo A. Sossi,⁵Audrey Bouvier,⁶Lu Chen,⁷Peng Ni
Proceedings of the National Academy of Sciences of the USA 122, e2519759122 Link to Article [https://doi.org/10.1073/pnas.251975912]
¹State Key Laboratory of Geological Processes and Mineral Resources, Hubei Key Laboratory of Planetary Geology and Deep-Space Exploration, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
²Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, United Kingdom
³National Institute of Polar Research, Tokyo 190-8518, Japan
⁴Department of Earth and Planetary Sciences, ETH Zürich, Zürich 8092, Switzerland
⁵Bayerisches Geoinstitut, University of Bayreuth, Bayreuth 95547 95440, Germany
⁶Wuhan Sample Solution Analytical Technology Co., Ltd.,Wuhan 430075, China
⁷Department of Earth, Planetary, and Space Sciences, The University of California Los Angeles, Los Angeles, CA 90095

The angrite parent body (APB) is the most volatile-depleted among known differentiated bodies in the Solar System, yet the mechanisms responsible remain poorly constrained. Here, we present high-precision nickel (Ni) isotope data from a suite of angrite samples to reconstruct the APB’s volatile depletion history. Plutonic angrites contain unusually high proportions of metallic iron and exhibit chondritic δ60/58Ni values (0.202 ± 0.028‰; per mille mass-dependent 60Ni/58Ni deviation relative to National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 986). These observations are consistent with a homogeneous Ni isotope composition of the APB after core formation and the subsequent incorporation of endogenous core material in plutonic angrites. In contrast, a dunite and megacrystic olivines from volcanic angrites, derived from the mantle, display suprachondritic δ60/58Ni values (0.4 to 0.7‰). We argue that these values are consistent with Ni loss via evaporation during a high-energy impact that follows an initial stage of volatile loss from a magma ocean generated by 26Al heating. Thermodynamic modeling confirms Ni to be more volatile than Mn, Fe, Si, and Mg during evaporation from silicate liquids, in agreement with the observed relative magnitude of isotopic fractionation. Volcanic angrite matrices show variable and often subchondritic δ60/58Ni values (down to −0.5‰), reflecting mixing with isotopically heavy megacrystic olivines and recondensation of light Ni vapor onto the crust. These findings imply that volatile elements are stratified (core–mantle–crust) in the APB and provide direct isotopic evidence for impact-driven vapor loss and recondensation on a differentiated planetary body.