Heterogeneous accretion and the moderately volatile element budget of Earth.
Several models exist to describe the growth and evolution of Earth; however, variables such as the type of precursor materials, extent of mixing, and material loss during accretion are poorly constrained. High-precision palladium-silver isotope data show that Earth's mantle is similar in 107Ag/109Ag to primitive, volatile-rich chondrites, suggesting that Earth accreted a considerable amount of material with high contents of moderately volatile elements. Contradictory evidence from terrestrial chromium and strontium isotope data are reconciled by heterogeneous accretion, which includes a transition from dominantly volatile-depleted to volatile-rich materials with possibly high water contents. The Moon-forming giant impact probably involved the collision with a Mars-like protoplanet that had an oxidized mantle, enriched in moderately volatile elements.
Schönbächler
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School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK. maria.schonbachler@manchester.ac.uk
Carlson
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Horan
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Mock
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Hauri
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