17:15 〜 19:15
[SIT21-P04] Deciphering solar system formation by linking the heterogeneity of short-lived and stable isotopes
Meteorites have evidence for the presence of short-lived nuclides (SLRs) sin the early solar system. Understanding the origin of these SLRs provides important insights into the early solar system evolution. Recent stable isotopic dichotomy-based spatial fingerprints of meteorites in the protoplanetary disk have provided vital clues for exploring the spatial distribution of SLRs in the early solar system. So far, various stable isotope dichotomies have been reported [1], and initial heterogeneities of SLRs in the inner and outer solar systems based on these dichotomies are being discovered. We recently determined the initial niobium-92 (92Nb) abundance in the outer solar system to be (92Nb/93Nb) = (3.0 ± 0.3) ×10–5 [2] using the NWA 6704 meteorite, a fresh igneous rock interpreted as an outer solar system sample due to similarities in stable isotope anomalies with carbonaceous chondrites (Δ17O, ε50Ti, ε54Cr; [3, 4]). This value is significantly higher than the initial value of (1.66 ± 0.10) × 10−5 [5] in the inner solar system, demonstrating that 92Nb was heterogeneously distributed within the protoplanetary disk and was enriched in the outer solar system. The obtained initial 92Nb/93Nb value is significantly higher than that predicted in the 92Nb synthesis model by Type Ia supernovae (SNIa). Therefore, our results suggest the need to consider another production site that selectively produces 92Nb. At the moment, only the ν-process in Type II supernovae (SNII) satisfies such a requirement. The heterogeneous contribution of ejecta from a nearby SNII to the early solar system has also been revealed by a recent study by [6] using correlated SLRs and stable isotope heterogeneities. They used the Al–Ti isotope correlation defined by the meteoritic samples for which (26Al/27Al)0 are anchored to their absolute Pb–Pb ages, and constrained the supernova explosion to have occurred at <2 pc from the core of the protosolar cloud shortly before it collapsed. The series of results supports the model that a nearby Type II supernova explosion formed our solar system.
References: [1] Burkhardt et al. (2019), [2] Haba et al. (2021), [3] Hibiya et al. (2019), [4] Sanborn et al. (2019), [5] Hibiya et al. (2023), [6] Iizuka et al. (2025).
References: [1] Burkhardt et al. (2019), [2] Haba et al. (2021), [3] Hibiya et al. (2019), [4] Sanborn et al. (2019), [5] Hibiya et al. (2023), [6] Iizuka et al. (2025).