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.

Automated summary

Calcium-aluminum-rich inclusions in meteorites provide important information about the early Solar System environment. Variations in vanadium and strontium isotopes in CAIs suggest that kinetic isotope effects during condensation and evaporation can explain anomalies previously attributed to solar particle irradiation. Researchers also found initial excesses of Be-10 and argue that CAIs likely formed at greater heliocentric distances than previously thought.