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

有许多方法可以重建地球表面过去的环境，但重建高层大气过去的条件是不可能的，因为缺乏来自这些高度的物理样本。虽然现代地球系统模型模拟了从地球表面到平流层及更远的气候动力学和大气化学，但没有办法在与目前不同的条件下对高层大气的结果进行地面实况。这项研究是一位宇宙化学家和一位气候动力学家之间的合作，研究了利用陨石熔融壳的高精度同位素测量重建过去气候期间高层大气温度和成分的可行性。具体来说，这项工作测试的假设，铁陨石的融合壳中的磁铁矿记录了在融合壳形成的时间和高度的大气中O2的同位素组成，这反过来又是臭氧浓度（质量独立的签名）以及多尔效应或其他质量相关的平流层过程的变化的代理。这项工作利用了现有的陨石收藏。如果这一试点项目成功，熔融地壳古大气代理可以应用于跨越过去300万年的大量南极陨石，并可以提供地球系统模型结果的测试。

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.