Molybdenum isotope anomalies in fine-grained refractory inclusions from Allende and Vigarano

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Nuclear isotope anomalies in meteorites and their components provide fundamental insights into the dynamical evolution and processing of matter in the solar nebula. Of particular interest in this respect are Ca,Al-rich inclusions (CAI), which, due to their antiquity, bear testimony to the earliest stages of disk evolution. Molybdenum isotopes are particularly well suited for investigating the origin of nucleosynthetic isotope heterogeneity in extraterrestrial materials. They possess the unique ability to distinguish between a deficit in s-process, and an excess in r-process Mo isotopes. In this study we aim to investigate the origin of nucleosynthetic isotope variations in CAI through an examination of Mo (and O) isotope heterogeneity. To this purpose we propose to conduct a systematic and comparative study on nucleosynthetic Mo isotope anomalies CAI from the carbonaceous chondrites Allende (CV3ox) and Vigarano (CV3red). A major focus of this study will be the investigation of Mo isotope anomalies in fine-grained refractory inclusions, some of which might be primary nebular condensates. Their genetic relation to coarse-grained (e.g., type B) CAI is largely unkwown. Specifically, we propose to: (i) explore the extent and origin of Mo isotope anomalies in fine-grained and coarse-grained CAI. (ii) examine the relationship between fine-grained and coarse-grained CAI by assessing as to whether these two groups of CAI exhibit systematically different Mo isotope systematics (i.e, r-excess vs. s-deficit), and (iii) investigate the origin of variable nucleosynthetic isotope anomalies in fine-grained CAI by assessing the effects of parent body and nebular processes on their isotope systematics. The effect of parent body alteration will be investigated through a comparative study of Mo isotope anomalies oxidized (Allende) and reduced (Vigarano) CV chondrites. The influence of nebular processes will be assessed through combined bulk Mo and in situ O isotope analyses on several CAI from Vigarano. This study will help to better establish the systematics and full extent of isotope anomalies in CAI, and will help to assess any genetic relationship between fine-grained and coarse-grained CAI. Ultimately, our study will provide new and firm constraints on the origin of nucleosynthetic isotope heterogeneity in the solar nebula during the earliest stages of solar system history.