A singular presolar SiC grain with extreme 29Si and 30Si excesses

An ion-imaging search of presolar SiC grains from the Murchison meteorite revealed one grain whose isotopic ratios are highly unusual: C-12/C-13 = 844 +/- 34, N-14/N-15 = 213 +/- 21, Si-29/Si-28 = (3.68 +/- 0.02) times solar, and Si-30/Si-28 = (4.29 +/- 0.04) times solar. Although several populations of presolar SiC grains have been identified, most of which originate in low-mass asymptotic giant branch stars, this is the first grain of its kind among similar to 20,000 SiC grains analyzed to date. Type II supernovae and Wolf-Rayet O binary systems are possible stellar sources.