Distribution of s -, r -, and p -process Nuclides in the Early Solar System Inferred from Sr Isotope Anomalies in Meteorites

[摘要] Nucleosynthetic isotope anomalies in meteorites allow distinguishing between the noncarbonaceous (NC) and carbonaceous (CC) meteorite reservoirs and show that correlated isotope anomalies exist in both reservoirs. It is debated, however, whether these anomalies reflect thermal processing of presolar dust in the disk or are primordial heterogeneities inherited from the solar system's parental molecular cloud. Here, using new high-precision ⁸⁴Sr isotope data, we show that NC meteorites, Mars, and the Earth and Moon are characterized by the same ⁸⁴Sr isotopic composition. This ⁸⁴Sr homogeneity of the inner solar system contrasts with the well-resolved and correlated isotope anomalies among NC meteorites observed for other elements, and most likely reflects correlateds - and ( r ,p )-process heterogeneities leading to ⁸⁴Sr excesses and deficits of similar magnitude, which cancel each other out. For the same reason there is no clearly resolved ⁸⁴Sr difference between NC and CC meteorites, because in some carbonaceous chondrites the characteristic ⁸⁴Sr excess of the CC reservoir is counterbalanced by an ⁸⁴Sr deficit resulting froms -process variations. Nevertheless, most carbonaceous chondrites exhibit ⁸⁴Sr excesses, which reflect admixture of refractory inclusions and more pronounceds -process heterogeneities in these samples. Together, the correlated variation ofs - and ( r ,p )-process nuclides revealed by the ⁸⁴Sr data of this study refute an origin of these isotope anomalies solely by processing of presolar dust grains, but points to primordial mixing of isotopically distinct dust reservoirs as the dominant process producing the isotopic heterogeneity of the solar system.