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Abiotic nitrogen reduction on the early Earth (see comments)

机译：地球早期的非生物氮减少（见评论）

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摘要

The production of organic precursors to life depends critically on the form of the reactants. In particular, an environment dominated by N2 is far less efficient in synthesizing nitrogen-bearing organics than a reducing environment rich in ammonia. Relatively reducing lithospheric conditions on the early Earth have been presumed to favour the generation of an ammonia-rich atmosphere, but this hypothesis has not been studied experimentally. Here we demonstrate mineral-catalysed reduction of N2, NO2- and NO3- to ammonia at temperatures between 300 and 800 degrees C and pressures of 0.1-0.4 GPa-conditions typical of crustal and oceanic hydrothermal systems. We also show that only N2 is stable above 800 degrees C, thus precluding significant atmospheric ammonia formation during hot accretion. We conclude that mineral-catalysed N2 reduction might have provided a significant source of ammonia to the Hadean ocean. These results also suggest that, whereas nitrogen in the Earth's early atmosphere was present predominantly as N2, exchange with oceanic, hydrothermally derived ammonia could have provided a significant amount of the atmospheric ammonia necessary to resolve the early-faint-Sun paradox.
机译：生命有机前体的产生关键取决于反应物的形式。特别地，由N 2为主的环境在合成含氮有机物中的效率远低于富含氨的还原性环境。据推测，地球早期岩石圈条件的相对减少有利于富氨大气的产生，但是这一假设尚未进行实验研究。在这里，我们证明了在地壳和海洋热液系统的典型条件下，在300至800摄氏度之间的温度和0.1-0.4 GPa的压力下，矿物催化的N2，NO2-和NO3-还原为氨。我们还表明，只有N2在800摄氏度以上才是稳定的，因此可以防止在热积聚过程中形成大量的大气氨。我们得出的结论是，矿物催化的N2还原可能已经为哈迪亚海洋提供了重要的氨来源。这些结果还表明，虽然地球早期大气中的氮主要以N2的形式存在，但与海洋热液衍生的氨进行交换可能会提供大量的大气氨，以解决早期太阳微弱的太阳悖论。

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