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，但由于缺乏来自这些高度的物理样本，重建高层大气中过去的条件是不可能的。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处的气候动力学和大气化学，但在与目前不同的条件下，没有办法对高层大气的结果进行实地验证。这项研究是由一位宇宙化学家和一位气候动力学家合作进行的，研究了利用陨石聚变壳的高精度同位素测量来重建过去气候期间高层大气温度和组成的可行性。具体来说，这项工作验证了一个假设，即铁陨石融合地壳中的磁铁矿记录了融合地壳形成的时间和高度大气中O2的同位素组成，这反过来又代表了臭氧浓度（一种与质量无关的特征）以及多尔效应或其他与质量相关的平流层过程的变化。这项工作利用了现有的陨石收藏。如果这个试点项目取得成功，融合地壳古大气代理可以应用于跨越过去300万年的南极陨石的大量收集，并可以为地球系统模型的结果提供测试。

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.