EAGER: Towards a Paleoproxy of Stratospheric Chemistry Using Meteorite Fusion Crusts

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There are many ways of reconstructing past environments at the Earth's surface, but reconstructing past conditions in the upper atmosphere has not been possible because of the lack of physical samples from these altitudes. While modern Earth System Models simulate climate dynamics and atmospheric chemistry from the Earth's surface to the stratosphere and beyond, there has been no way to ground-truth the results for the upper atmosphere for conditions that are different from those at present. This study, a collaboration between a cosmochemist and a climate dynamicist, investigates the feasibility of reconstructing upper atmosphere temperature and composition during past climates using high precision isotopic measurements of the fusion crust of meteorites. Specifically, the work tests the hypothesis that magnetite in the fusion crust of iron meteorites records the isotopic composition of O2 in the atmosphere at the time and altitude that the fusion crust formed, which in turn is a proxy for ozone concentration (a mass-independent signature) as well as variations in the Dole Effect or other mass-dependent stratospheric processes. The work takes advantage of existing collections of meteorites. If this pilot project is successful, the fusion crust paleo-atmosphere proxy could be applied to the vast collection of Antarctic meteorites, which spans the past 3 million years, and could provide tests of Earth System Model results.