Remnants of shooting stars are preserved in form of cosmic spherules in ice and sediments. The extraterrestrial material is heated and melted upon atmospheric entry and is collected at the Earth's surface as cosmic spherules. A fraction of cosmic spherules (I‐type cosmic spherules) sources from extraterrestrial Fe,Ni metal. These metal particles melt and become oxidized in the atmosphere. The oxygen in the resulting oxides (magnetite, wüstite) sources entirely from the atmosphere. Here, we demonstrate that I‐type cosmic spherules can be used to reconstruct the triple oxygen isotope anomaly of the past atmosphere, which provides information on the gross primary productivity and/or paleo‐CO₂ levels. We present a calibration of the proxy using Antarctic cosmic spherules. We further introduce Δ′⁵⁶Fe and demonstrate that triple iron isotopes can be used to obtain information about the underlying fractionation mechanism (e.g., kinetic vs. equilibrium fractionation).

中文翻译：

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I型宇宙小球替代大气的Δ′17O —用季风空气校准

流星的残留物以宇宙小球的形式保存在冰和沉积物中。进入大气层后，地外物质被加热并融化，并以宇宙小球的形式收集在地球表面。宇宙球的一部分（I型宇宙球）来自地球外的铁，镍金属。这些金属粒子在大气中熔化并被氧化。生成的氧化物（磁铁矿，镁橄榄石）中的氧气完全来自大气。在这里，我们证明了I型宇宙球可用于重建过去大气的三重氧同位素异常，从而提供有关总初级生产力和/或古二氧化碳₂水平的信息。我们提出了使用南极宇宙小球对代理的校准。我们进一步介绍Δ' ⁵⁶Fe和Fe证明了三重铁同位素可用于获得有关潜在的分馏机理的信息（例如，动力学与平衡分馏）。