Light elements in irons and metal-rich meteorites: Their isotopic distribution and evolution in the protoplanetary disk

ongoing

Knowledge of the light element (H, C, N) characteristics of planetary building blocks is key to our understanding of the development of habitable conditions on Earth. Since 'magmatic' iron meteorites originate from the metallic cores of the earliest, differentiated planetesimals, they may preserve a record of H, C, and N isotopic variations in the inner and outer solar system during the first stages of planetary accretion. Based on novel multi-light-element isotopic analyses of irons and other Fe-Ni alloy-rich meteorites and experimental simulations, project IRONIS aims to answer the fundamental questions of (i) how the distributions of H, C, and N (and their carrier phases) evolved in space and time within the earliest stages of the protoplanetary disk, and (ii) how H, C, and N were distributed between metals and silicates during planetesimal accretion, differentiation, and subsequent evolution. A major objective is to develop novel secondary ion mass spectrometry protocols for analyzing H, C, and N in situ in Fe-Ni alloy, and to combine these with 'bulk' N-noble gas analyses by static noble gas mass spectrometry. The originality and uniqueness of project IRONIS thus lies in the coupling of two state-of the-art analytical techniques, which allow the quantification of any solar gas and cosmogenic nuclide contributions. Only once the effects of these secondary components are understood, can spatiotemporal isotopic variations in the protoplanetary disk be investigated. In parallel, new cross-calibrated N analyses of experimental run products will provide constraints on the degree of N isotopic fractionation during alloy-silicate partitioning, and will permit us to assess if the N isotopic compositions of irons represent a primary feature of their parent bodies. Ultimately, by investigating the remnants of the first planetesimal populations, project IRONIS will provide new fundamental insights into the cosmochemical history and evolution of life-forming light elements.