Pre-irradiation effects in CAIs from primitive meteorites
BORIS DOI
Abstract
Calcium–aluminum-rich inclusions (CAIs) are the oldest known solids in the solar system and record key processes from the earliest stages of planetary formation. This thesis investigates whether CAIs experienced irradiation by solar or galactic cosmic rays before they were incorporated into their parent bodies. CAIs from CV, CM, and CK carbonaceous chondrites, together with adjacent matrix samples, were analyzed. High-resolution micro-CT imaging was used to locate and extract the inclusions, followed by SEM characterization and noble gas mass spectrometry. Concentrations of He, Ne, Ar, and selected Kr isotopes were measured to identify possible excess cosmogenic components. Although large variations in noble gas concentrations were observed between individual CAIs, no consistent evidence for pre-accretionary irradiation was found. The data indicate that the measured cosmic-ray exposure ages are consistent with irradiation within the meteoroid rather than before parent-body accretion. Variations are best explained by differences in chemical composition, shielding conditions, and secondary alteration processes. These results argue against prolonged storage of CAIs in irradiation-rich regions and instead support models involving rapid transport and storage in shielded regions of the protoplanetary disk. Overall, this work places new constraints on the early transport, storage, and irradiation history of CAIs in the young solar system.
Date of Publication
2025
Year of graduation
2025
Theses Type
dissertation
Subject(s)
Language(s)
en
Author(s)
Faculty/Graduate School
Institute
Access(Rights)
open.access
Primary OA Publication
true