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arXiv 2209.11264astro-ph.EP
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低温N2-CH4等离子体放电实验揭示的土卫六大气化学

Titan Atmospheric Chemistry Revealed by Low-temperature N2-CH4 Plasma Discharge Experiments

Chao He, Joseph Serigano, Sarah M. Horst, Michael Radke, Joshua A. Sebree

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Accepted in ACS Earth and Space Chemistry, 6 figures
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摘要：

土卫六的N2-CH 4大气中的化学物质产生了复杂的有机气溶胶。化学过程和由此产生的有机化合物仍然远未被理解，尽管广泛的观察，实验室和理论模拟已经大大改善了土卫六大气层的物理和化学约束。在这里，我们进行了一系列的泰坦大气模拟实验与N2-CH 4气体混合物和调查的影响，初始CH 4的比例，压力和流量上的生产率和气体和固体产品的组成在泰坦的相关温度（100 K）的第一次。我们发现，气体和固体产物的生产率增加，增加甲烷比例。含氮物质具有比气体产物中的烃高得多的产率，并且固体产物的N-对-C比率与具有相同CH 4比率的先前等离子体模拟相比似乎是最高的。在低温模拟实验中，氮的掺入程度更大，这表明温度可能在土卫六寒冷大气中的氮掺入中发挥重要作用。我们还发现，H2是占主导地位的气体产品，并作为新的有机分子在实验中的生产率的指标，和CH 2NH可能大大有助于将碳和氮的固体颗粒。压力和流速影响气体混合物暴露于能源的时间量，并因此影响由等离子体放电引发的N2-CH 4化学，强调了能量通量在泰坦大气化学中的影响。

英文摘要：

Chemistry in Titan's N2-CH4 atmosphere produces complex organic aerosols. The chemical processes and the resulting organic compounds are still far from understood, although extensive observations, laboratory, and theoretical simulations have greatly improved physical and chemical constraints on Titan's atmosphere. Here, we conduct a series of Titan atmosphere simulation experiments with N2-CH4 gas mixtures and investigate the effect of initial CH4 ratio, pressure, and flow rate on the production rates and composition of the gas and solid products at a Titan relevant temperature (100 K) for the first time. We find that the production rate of the gas and solid products increases with increasing CH4 ratio. The nitrogen-containing species have much higher yield than hydrocarbons in the gas products, and the N-to-C ratio of the solid products appears to be the highest compared to previous plasma simulations with the same CH4 ratio. The greater degree of nitrogen incorporation in the low temperature simulation experiments suggests temperature may play an important role in nitrogen incorporation in Titan's cold atmosphere. We also find that H2 is the dominant gas product and serves as an indicator of the production rate of new organic molecules in the experiment, and that CH2NH may greatly contribute to the incorporation of both carbon and nitrogen into the solid particles. The pressure and flow rate affect the amount of time of the gas mixture exposed to the energy source and therefore impact the N2-CH4 chemistry initiated by the plasma discharge, emphasizing the influence of the energy flux in Titan atmospheric chemistry.

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