Speaker: Dr. Yung-Hsin Liu (ASIES)
Time & Venue: 14:20, S101
Title: The Early Solar System Evolution Inferred from Nucleosynthetic Isotope Anomalies in FUN Calcium-Aluminum-Rich Inclusions
Abstract:
Meteorites contain tiny remnants of dust grains that formed around earlier generations of stars that had survived the birth of the solar system. These presolar grains carry distinctive nucleosynthetic isotopic anomalies, which reflect their stellar origins. Although extensive mixing and processing in the protoplanetary disk largely homogenized these signatures, measurable anomalies are still preserved in meteorites and their components. These isotopic records provide important clues to the source materials of the solar system, the relationships among planetary bodies, and the transport and processing of matter in the early solar system.
Calcium-aluminum-rich inclusions (CAIs) are the oldest known solids formed in the solar system. Condensed directly from hot gas near the proto-Sun, CAIs preserved a unique record of the chemical and isotopic environment that existed during the earliest stages of solar system formation. Their compositions were influenced by material inherited from multiple stellar sources, including supernovae that contributed short-lived radionuclides, such as 26 Al, neutron-rich isotopes, and r-process nuclides. A rare subgroup of CAIs, known as FUN (fractionation and unknown nuclear effects) CAIs, display unusual isotopic characteristics while sharing all the mineralogical and petrographic features as the “normal” CAIs. Because FUN CAIs are extremely rare, their origin and significance remain poorly understood. In this study, we identified a new FUN CAI from the Allende CV3 chondrite using a laser-based Mg isotope analysis technique. By combining our results with previously published data, we find that many FUN CAIs show a unique characteristic of deficits in 26 Al and 30 Si, consistent with contributions from AGB stars. However, the supernovae related neutron-rich isotopes show either positive or negative anomalies. These observations support the idea that FUN CAIs represent a reservoir of stellar material inherited from the galaxy before the formation of our solar system, and subsequently isolated through thermal processing in the early protoplanetary disk. A key unresolved question is how FUN and normal CAIs are related and whether they formed in spatially distinct regions or at different times during the evolution of the early solar system.