Meteorite impacts on ancient oceans opened up multiple NH3 production pathways
Meteorite impacts on ancient oceans opened up multiple NH3 production pathways
复制标题
陨石对古代海洋的影响开辟了多种 NH3 生产途径
DOI：
10.1039/c7cp00870h
复制
发表时间：
2017
影响因子：
3.3
通讯作者：
and Shigenori Tanaka
中科院分区：
文献类型：
--
作者：
Kohei Shimamura;Fuyuki Shimojo;Aiichiro Nakano;and Shigenori Tanaka
Nakazawa等人从2005年开始的最近一系列冲击实验（例如[Nakazawa等人，地球行星。Sci.信件：2005年，235，356]）提出，陨石撞击古代海洋会产生相当数量的NH3的早期地球从大气中的N2和海洋H2O通过还原陨石铁。为了澄清的机制，我们模仿的影响事件进行多尺度冲击技术为基础的从头算分子动力学的密度泛函理论的框架下，结合多尺度冲击技术（MSST）模拟。我们之前的模拟与实验的冲击能量接近，揭示了冲击压缩期间皮秒级快速NH3的产生[Shimamura等人，Sci.代表：2016，6，38952]。研究还表明，N2的还原与固氮酶的催化作用有关。在这项研究中，我们进行了MSST-AIMD模拟，以调查更高能量的陨石撞击产生的物质，这些物质更接近早期地球上的预期值。发现NH3的产生量进一步增加。我们还发现，增加的NH3生产是由于在增加的冲击能量的多个反应机制的出现。我们阐明了N2的还原不仅归因于缔合机制，而且还归因于Haber-Bosch过程中所见的解离机制和通过肼离子的机制。这些能够提供大量NH3的多种生产机制的出现将比以前认为的更强烈地支持来自最近实验的建议，即，冲击引起的NH3产生在地球生命的起源中发挥了关键作用。
A recent series of shock experiments by Nakazawa et al. starting in 2005 (e.g. [Nakazawa et al., Earth Planet. Sci. Lett., 2005, 235, 356]) suggested that meteorite impacts on ancient oceans would have yielded a considerable amount of NH3 to the early Earth from atmospheric N2 and oceanic H2O through reduction by meteoritic iron. To clarify the mechanisms, we imitated the impact events by performing multi-scale shock technique-based ab initio molecular dynamics in the framework of density functional theory in combination with multi-scale shock technique (MSST) simulations. Our previous simulations with impact energies close to that of the experiments revealed picosecond-order rapid NH3 production during shock compression [Shimamura et al., Sci. Rep., 2016, 6, 38952]. It was also shown that the reduction of N2 took place with an associative mechanism as seen in the catalysis of nitrogenase enzymes. In this study, we performed an MSST-AIMD simulation to investigate the production by meteorite impacts with higher energies, which are closer to the expected values on the early Earth. It was found that the amount of NH3 produced further increased. We also found that the increased NH3 production is due to the emergence of multiple reaction mechanisms at increased impact energies. We elucidated that the reduction of N2 was not only attributed to the associative mechanism but also to a dissociative mechanism as seen in the Haber–Bosch process and to a mechanism through a hydrazinium ion. The emergence of these multiple production mechanisms capable of providing a large amount of NH3 would support the suggestions from recent experiments much more strongly than was previously believed, i.e., shock-induced NH3 production played a key role in the origin of life on Earth.