UC Davis

A large-scale isotopic dichotomy has emerged among Solar System materials in recent years based on correlated isotopic systematics of O, Cr, Ti, Mo, Ru, and W. With improved analytical precision, nucleosynthetic isotopic anomalies observed in meteorites have become a powerful tool for establishing genetic links between different classes of meteorites. One of the weakest links in planetary genealogy in the current literature is the disconnection between stony meteorites (characterized using O, Cr, and Ti isotopes) and iron meteorites (studied using siderophile elements such as Mo, Ru and W). We overcome this difficulty by searching for and extracting silicate and oxide phases (chromites) from the major groups of iron meteorites and pallasites and measuring nucleosynthetic Cr isotopic composition combined with O isotopic composition.In this study, we use nucleosynthetic anomalies of 54Cr combined with Δ17O to explore 1) a possible genetic connection between the IAB irons and winonaites and test the impact origin of IAB irons; 2) the IIE iron meteorites and their potential connection to H chondrites; and 3) the genealogy of the Main Group Pallasites (PMG) and their proposed link to IIIAB irons, and test for any isotopic evidence of impact mixing; and 4) the Cr-O isotopic reservoir of the Eagle Station Pallasites (PES) group and two ungrouped irons (Bocaiuva and NWA 176) and their potential genetic links with any known carbonaceous chondrite group. We also study two pyroxene pallasites, Choteau and Vermillion, to determine if they are derived from any of the known meteorite groups. We find that the silicates and metal phases IAB irons are derived from two separate parent bodies, providing conclusive evidence for the impact origin of IAB irons. We also find that IIE irons and H chondrites are genetically linked, derived from a common isotopic reservoir, and most likely shared a common parent body. Moreover, we show evidence that Main Group Pallasites are not genetically linked to IIIAB irons and are derived from distinct isotopic reservoirs. Further, we show that Eagle Station Pallasites may be derived from a differentiated CO-CK chondrite like parent body. Additionally, the pyroxene pallasites Choteau and Vermillion are derived from two distinct parent bodies formed in the inner Solar System, not related to either the PMG or the PES. This study highlights the diverse origins of pallasites forming throughout the Solar System on multiple parent bodies, probably through different processes, and demonstrates the effectiveness of nucleosynthetic isotopic anomalies as a tool for genetic tracing of planetary materials (isotopic forensics).