Fossil Records Of Early Solar Irradiation And Cosmolocation Of The Cai Factory: A Reappraisal

Calcium-aluminum-rich inclusions (CAIs) in meteorites carry crucial information about the environmental conditions of the nascent Solar System prior to planet formation. Based on models of 50V-Be-10 co-production by in-situ irradiation, CAIs are considered to have formed within similar to 0.1 AU from the proto-Sun. Here, we present vanadium (V) and strontium (Sr) isotopic co-variations in fine- and coarse-grained CAIs and demonstrate that kinetic isotope effects during partial condensation and evaporation best explain V isotope anomalies previously attributed to solar particle irradiation. We also report initial excesses of Be-10 and argue that CV CAIs possess essentially a homogeneous level of Be-10, inherited during their formation. Based on numerical modeling of 50V-Be-1(0) co-production by irradiation, we show that CAI formation during protoplanetary disk build-up likely occurred at greater heliocentric distances than previously considered, up to planet-forming regions (similar to 1AU), where solar particle fluxes were sufficiently low to avoid substantial in-situ irradiation of CAIs.