Redox state during core formation on asteroid 4-Vesta

E.A. Pringle, P.S. Savage, J. Badro, J.-A. Barrat, F. Moynier

Research output: Contribution to journalArticlepeer-review

43 Citations (Scopus)


Core formation is the main differentiation event in the history of a planet. However, the chemical composition of planetary cores and the physicochemical conditions prevailing during core formation remain poorly understood. The asteroid 4-Vesta is the smallest extant planetary body known to have differentiated a metallic core. Howardite, Eucrite, Diogenite (HED) meteorites, which are thought to sample 4-Vesta, provide us with an opportunity to study core formation in planetary embryos.Partitioning of elements between the core and mantle of a planet fractionates their isotopes according to formation conditions. One such element, silicon, shows large isotopic fractionation between metal and silicate, and its partitioning into a metallic core is only possible under very distinctive conditions of pressure, oxygen fugacity and temperature. Therefore, the silicon isotope system is a powerful tracer with which to study core formation in planetary bodies. Here we show through high-precision measurement of Si stable isotopes that HED meteorites are significantly enriched in the heavier isotopes compared to chondrites. This is consistent with the core of 4-Vesta containing at least 1. wt% of Si, which in turn suggests that 4-Vesta's differentiation occurred under more reducing conditions (δIW~-4) than those previously suggested from analysis of the distribution of moderately siderophile elements in HEDs.
Original languageEnglish
Pages (from-to)75-82
Number of pages8
JournalEarth and Planetary Science Letters
Publication statusPublished - 1 Jul 2013


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