Rimmer Paul B, Shorttle Oliver
Cavendish Laboratory, University of Cambridge, JJ Thomson Ave, Cambridge CB3 0HE, UK.
Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA, UK.
Life (Basel). 2024 Apr 11;14(4):498. doi: 10.3390/life14040498.
Giant impacts can generate transient hydrogen-rich atmospheres, reducing atmospheric carbon. The reduced carbon will form hazes that rain out onto the surface and can become incorporated into the crust. Once heated, a large fraction of the carbon is converted into graphite. The result is that local regions of the Hadean crust were plausibly saturated with graphite. We explore the consequences of such a crust for a prebiotic surface hydrothermal vent scenario. We model a surface vent fed by nitrogen-rich volcanic gas from high-temperature magmas passing through graphite-saturated crust. We consider this occurring at pressures of 1-1000bar and temperatures of 1500-1700 ∘C. The equilibrium with graphite purifies the leftover gas, resulting in substantial quantities of nitriles (0.1% HCN and 1ppm HCN) and isonitriles (0.01% HNC) relevant for prebiotic chemistry. We use these results to predict gas-phase concentrations of methyl isocyanide of ∼1 ppm. Methyl isocyanide can participate in the non-enzymatic activation and ligation of the monomeric building blocks of life, and surface or shallow hydrothermal environments provide its only known equilibrium geochemical source.
巨大撞击可产生富含氢的短暂大气层，从而减少大气中的碳。被还原的碳会形成阴霾，沉降到地表，并可能融入地壳。一旦受热，大部分碳会转化为石墨。结果是，太古代地壳的局部区域可能富含石墨。我们探讨了这种地壳对于前生物表面热液喷口情景的影响。我们模拟了一个由来自高温岩浆的富氮火山气体通过石墨饱和地壳供给的表面喷口。我们考虑这种情况发生在1 - 1000巴的压力和1500 - 1700摄氏度的温度下。与石墨的平衡净化了剩余气体，产生了大量与前生物化学相关的腈（0.1%的HCN和1ppm的HCN）和异腈（0.01%的HNC）。我们利用这些结果预测气相中甲基异腈的浓度约为1ppm。甲基异腈可参与生命单体构建块的非酶促活化和连接，而表面或浅层热液环境是其唯一已知的平衡地球化学来源。
