Emily A. Pringle^1,2, Paul S. Savage¹, Matthew G. Jackson³, Jean-Alix Barrat⁴ and Frédéric Moynier^1,2

¹Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
²Institut de Physique du Globe de Paris, Université Paris Diderot, 75005 Paris, France
³Department of Earth Science, University of California, Santa Barbara, CA 93109, USA
⁴Université Européenne de Bretagne, Université de Brest, CNRS UMR 6538 (Domaines Océaniques), I.U.E.M., Place Nicolas Copernic, F-29280 Plouzané Cedex, France

The presence or absence of variations in the mass-independent abundances of Si isotopes in bulk meteorites provides important clues concerning the evolution of the early solar system. No Si isotopic anomalies have been found within the level of analytical precision of 15 ppm in ²⁹Si/²⁸Si across a wide range of inner solar system materials, including terrestrial basalts, chondrites, and achondrites. A possible exception is the angrites, which may exhibit small excesses of ²⁹Si. However, the general absence of anomalies suggests that primitive meteorites and differentiated planetesimals formed in a reservoir that was isotopically homogenous with respect to Si. Furthermore, the lack of resolvable anomalies in the calcium-aluminum-rich inclusion measured here suggests that any nucleosynthetic anomalies in Si isotopes were erased through mixing in the solar nebula prior to the formation of refractory solids. The homogeneity exhibited by Si isotopes may have implications for the distribution of Mg isotopes in the solar nebula. Based on supernova nucleosynthetic yield calculations, the expected magnitude of heavy-isotope overabundance is larger for Si than for Mg, suggesting that any potential Mg heterogeneity, if present, exists below the 15 ppm level.

Reference
Pringle EA, Savage PS, Jackson MG, Barrat J-A and Moynier F (in press) Si Isotope Homogeneity of the Solar Nebula. The Astrophysical Journal 779:123
[doi:10.1088/0004-637X/779/2/123]

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