The Origin of Nitrogen on Earth: Implications from Isotope and Petrologic Studies of Planetary Materials at the Sub-Micrometer Scale.

氮是地球大气中最丰富的成分，是地球生物圈进化的关键元素。岩石行星地球、火星和金星各自的同位素组成不同于太阳和原太阳星云（PSN）。因此，来自太阳星云的其他成分一定对地球上的氮有很大的贡献。顽火辉石球粒陨石（ECs）的同位素特征表明，它们与少量普通球粒陨石和碳质球粒陨石材料一起，是构成原始地球的最佳模拟材料。其他研究的模型计算认为一组无球粒陨石是最合适的。体积化学表明，我们的太阳系材料样本还远远不够完整，陨石记录中有很大一部分与地球有关。这就强调了有必要对现有陨石样品中含氮相的库存进行表征，以便对缺失的部分进行预测。在这个项目的第一阶段，很明显，ECs中已知的n载流子不能占体积氮的总量，这表明其他相作为宿主材料。几个碳质球粒陨石中的有机物（OM）与陆地大气相比，在15N中具有较高的富集度。这些富集是陨石母体上流体相互作用的结果，而不是直接继承自原太阳云。对这些物质的化学功能的研究仍在进行中，但这一观察结果的一个含义是，为原始地球提供氮的球粒质有机物质可能跨越比最初预期的更广泛的（结构和化学）范围。我将继续研究各种球粒陨石中的含氮物质，主要集中在ec中的金属，硫化物和硅酸盐。此外，还将继续对顽辉石和普通球粒陨石中的无机n载体进行定量研究，并对CO和CV球粒陨石的OM盘存进行研究。样本集将扩展到与陆地构造块有潜在关系的无球粒陨石。样品的表征将通过SEM和SEM- eds进行。n同位素研究将由NanoSIMS进行。氮通常用SIMS检测为CN-，这通常限制了传统的n同位素测量也含有碳的相。因此，一些样品将采用c浸渍法制备，以提高cn产率。无碳相的N同位素也可以用14,15n +来研究。样品将被选择并准备用于透射电子显微镜的结构分析。该项目将扩大含氮相及其n同位素组成的库存，最终将有助于确定对地球氮有贡献的载体的性质。

Nitrogen, the most abundant component in Earth’s atmosphere, was a key element for the evolution of Earth’s biosphere. The respective isotopic compositions of the rocky planets Earth, Mars and Venus differ from those of the Sun and the Protosolar Nebula (PSN). Thus, other components from the solar nebula must have significantly contributed to terrestrial nitrogen. Isotopic signatures of the enstatite chondrites (ECs) suggest them as the best analogue material for the building blocks of the primordial Earth, together with a smaller fraction of ordinary chondrite and carbonaceous chondrite material. Model calculations from other studies consider angrites, a group of achondrites, as best fit. Bulk chemistry indicates that our sample set of Solar System materials is far from complete, with a significant portion contributing to Earth missing from the meteorite record. This emphasizes the necessity to characterize the inventory of nitrogen-bearing phases in the available sets of meteoritic samples, to allow predictions about the missing fraction. During the first period of this project, it became evident that the known N-carriers in the ECs cannot account for the total amount of bulk nitrogen, indicating other phases as host materials. Organic material (OM) in several carbonaceous chondrites contained high enrichments in 15N compared to the terrestrial atmosphere. These enrichments were the result of fluid interaction on the meteoritic parent body, and not directly inherited from the protosolar cloud. Investigation of the chemical functionalities of these materials is still in progress, but one of the implications of this observation is that the chondritic organic material that contributed nitrogen to the primordial Earth might span an even wider (structural and chemical) range than initially anticipated. I will continue the investigation of nitrogen-bearing materials in various chondritic meteorites, with the main focus on metal, sulfides, and silicates in ECs. In addition, the quantification of the anorganic N-carriers in enstatite and ordinary chondrites will be continued, and the OM inventory of CO and CV chondrites will be studied. The sample set will be expanded to achondrites that have potential relations to the terrestrial building blocks. Sample characterization will be carried out by SEM and SEM-EDS. N-isotopic investigations will be conducted by NanoSIMS. Nitrogen is typically detected with SIMS as CN-, which normally restricts conventional N-isotopic measurements to phases that also contain carbon. Thus, some samples will be prepared by C-impregnation to enhance the CN-yield. The N isotopes of C-free phases can also be studied by using 14,15N+. Samples will be selected and prepared for structural analysis by transmission electron microscopy. This project will expand the inventory of N-bearing phases and their N-isotopic compositions, which ultimately will help to determine the nature of the carriers contributing to Earth’s nitrogen.