Constraints on the Formation Age of Cometary Material from the NASA Stardust Mission

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Science  25 Feb 2010:
DOI: 10.1126/science.1184741


We measured the 26Al-26Mg isotope systematics of a ~5-μm refractory particle, Coki, returned from comet 81P/Wild 2 in order to relate the time scales of formation of cometary inclusions to their meteoritic counterparts. The data show no evidence of radiogenic 26Mg and define an upper limit to the abundance of 26Al at the time of particle formation of 26Al/27Al <1 × 10−5. The absence of 26Al indicates Coki formed >1.7 Ma after the oldest solar system solids, Ca-Al-rich inclusions (CAIs). The data presented here suggest that high temperature inner solar system material formed, was subsequently transferred to the Kuiper Belt, and incorporated into comets several million years following CAI formation.