Isotopic and Geochemical Studies of Meteorites: Constraints on Processes and Time Scales in the Early Solar System and Implications for Early History of the Earth

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9725659 Wadhwa The main goal of this proposal is to gain better constraints on early condensation, accretion and differentiation processes and their chronology in the solar system through geochemical and isotopic studies of meteorites. The proposed research has implications not only for the formation of planetesimals in the asteroidal belt, but also for the early history of the Earth. The work plan is comprised of two main lines of research on undifferentiated and differentiated meteorites and involves isotopic measurements of long-lived and short-lived ("extinct") chronometric systems. The first project involves the determination of Al-Mg, Mn-Cr and initial Sr isotopic systematics in the refractory calcium-aluminum-rich inclusions (CAIs) from primitive carbonaceous chondrites and has implications for high-resolution chronology of the early solar system relative to these earliest formed condensates. The second project involves the determination of Sm-Nd systematics of phosphates in pallasites to establish the timing of core-mantle segregation on their asteroidal parent body. The constraints offered by these two projects will provide a better resolved picture of the timing and geochemical consequences of the early processes operational in the inner solar system.