| Summary: | The Mo and Ru isotopic compositions of meteorites and the bulk silicate Earth (BSE) hold important clues about the provenance of Earth's building material. Prior studies have argued that non-carbonaceous (NC) and carbonaceous (CC) meteorite groups together define a Mo-Ru 'cosmic' correlation, and that the BSE plots on the extension of this correlation. These observations were taken as evidence that the final 10–15% of Earth's accreted material derived from a homogeneous inner disk reservoir with an enstatite chondrite-like isotopic composition. Here, using new Mo and Ru isotopic data for previously uninvestigated meteorite groups, we show that the Mo-Ru correlation only exists for NC meteorites, and that both the BSE and CC meteorites fall off this Mo-Ru correlation. These observations indicate that the final stages of Earth's accretion were heterogeneous and consisted of a mixture of NC and CC materials. The Mo-Ru isotope systematics are best accounted for by either an NC heritage of the late veneer combined with a CC heritage of the Moon-forming giant impactor, or by mixed NC-CC compositions for both components. The involvement of CC bodies in the late-stage accretionary assemblage of Earth is consistent with chemical models for core-mantle differentiation, which argue for the addition of more oxidized and volatile-rich material toward the end of Earth's formation. As such, this study resolves the inconsistencies between homogeneous accretion models based on prior interpretations of the Mo-Ru systematics of meteorites and the chemical evidence for heterogeneous accretion of Earth. © 2020 The Author(s). Published by Elsevier Under a Creative Commons license - Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) Received 19 September 2019, Revised 30 November 2019, Accepted 30 December 2019, Available online 17 January 2020. We gratefully acknowledge Addi Bischoff, Knut Metzler, the Institute of Meteoritics, University of New Mexico, and NASA for providing samples. US Antarctic ...
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