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: ¹²C/¹³C = 844 ± 34, ¹⁴N/⁵N = 213 ± 21, ²⁹Si/²⁸Si = (3.68 ± 0.02) times solar, and ³⁰Si/²⁸Si = (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 ∼20,000 SiC grains analyzed to date. Type II supernovae and Wolf-Rayet O binary systems are possible stellar sources.