Hf-W chronology of early solar system processes

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The time interval from formation of the first solids in the solar system to the formation of planetesimals lasted only a few million years (Myr). The physical and chemical processes that occurred during this brief interval set the conditions for the origin and evolution of the planets in the early solar system. To reconstruct these processes, it is essential to obtain very precise ages that date real events or that provide information on the rates of processes. Such high precision ages can be obtained with shortlived isotopes, such as 182Hf, which decays to 182W (t1/2 ~9 Myr). Due to the geochemical properties of Hf and W, the decay system is ideally suited to constraining the time of metal formation or silicatemetal equilibration at any scale. A major goal of this project will be to obtain highly precise ages (±1 Myr or better) for the formation of different chondrite groups as well as mesosiderites and pallasites. Because it is now well established that chondrites are not the oldest objects in the solar system, their role in the chemical and mineralogical evolution of the solar system has become less clear. Therefore, we plan to construct an absolute time frame for the chondrule-forming process(es) and relate this to other differentiation processes that occurred during the first 10 Myr of our solar system.