Stardust as nucleation seeds for the earliest solids in the Solar System

Recent reports of extreme strontium-84 excesses in primitive Solar System condensates, known as fine-grained calcium-aluminum-rich inclusions (fg-CAIs), suggest that presolar stardust may be preserved in refractory meteoritic components. This is at odds with preconceptions that presolar grains were completely vaporized in the CAI-forming region. Here, we reappraise the role of presolar materials in early condensation and overall disk heterogeneity by isolating strontium from primary fg-CAI phases. We demonstrate that extreme strontium-84 anomalies are likely hosted in a subpopulation of CAI oxides. The anomalies of primitive noncarrier phases are shown to be attenuated but correlated with the abundance of presolar precursors, which suggests that carriers exert leverage on ensuing condensate compositions. We propose that this relationship between isotope anomalies in refractory CAI components stems from stardust acting as nucleation seeds for the earliest solids formed in the Solar System.