Lunar and Planetary Science Conference XXXV
Solar oxygen contains an anomalously high fraction of 18O. I here attribute that excess 18O to the supernova starburst initiated by the merger of a satellite gal-axy with the Milky Way. This starburst spawned  the mixing line seen in the AGB star compositions whose SiC dust constitutes the observed mainstream SiC grains. The number of starburst AGB stars born in this short time interval excceds that born locally by the steady rate of galactic star birth, so they dominate the SiC grains. Given that, the anomalously large 18O/17O ratio in the sun resulted from these presolar circumstances for the origin of the sun.
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