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Contemporaneous formation of chondrules and refractory inclusions in the early Solar System


Chondrules and calcium-aluminium-rich inclusions (CAIs) are preserved materials from the early history of the Solar System, where they resulted from thermal processing of pre-existing solids during various flash heating episodes which lasted for several million years1. CAIs are believed to have formed about two million years before the chondrules2,3,4,5. Here we report the discovery of a chondrule fragment embedded in a CAI. The chondrule's composition is poor in 16O, while the CAI has a 16O-poor melilite (Ca, Mg, Al-Silicate) core surrounded by a 16O-rich igneous mantle. These observations, when combined with the previously reported CAI-bearing chondrules6,7,8,9, strongly suggest that the formation of chondrules and CAIs overlapped in time and space, and that there were large fluctuations in the oxygen isotopic compositions in the solar nebula probably synchronizing astrophysical pulses.

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Figure 1: Back-scattered electron image of the chondrule-bearing CAI.
Figure 2: Oxygen-isotopic composition of minerals in the chondrule-bearing CAI.
Figure 3: Schematic view of CAI and chondrule formation.


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We thank J. T. Wasson and A. E. Rubin for loaning us the thin section and for discussions. We also thank A. Meibom, A. N. Krot and T. J. Fagan for discussions and for improving the English of this Letter. This work was supported by Monbu-Kagaku-sho grants.

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Correspondence to Hisayoshi Yurimoto.

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Itoh, S., Yurimoto, H. Contemporaneous formation of chondrules and refractory inclusions in the early Solar System. Nature 423, 728–731 (2003).

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