The Physical Origin of the Venus Low Atmosphere Chemical Gradient
The Physical Origin of the Venus Low Atmosphere Chemical Gradient
复制标题
金星低大气层化学梯度的物理起源
DOI：
10.3847/1538-4357/ab27bd
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
F. García
中科院分区：
文献类型：
--
作者：
D. Cordier;D. Bonhommeau;S. Port;V. Chevrier;S. Lebonnois;F. García
金星与地球有许多相似之处，但同时，它的一些特征也非常原始。尤其是它的大气层，在地面上发现高压和高温。在这些条件下，金星大气的主要成分二氧化碳是超临界流体。对Vega-2探测数据的分析揭示了位于地面以上最后几公里的区域的高度不稳定性。最近的研究提出了一种基于分子氮丰度垂直梯度存在的解释，约为每米5 ppm。我们的目标是确定哪些物理过程可能导致金星深层大气中这种有趣的氮梯度的建立。使用一个适当的状态方程的二元混合物CO2-N2在超临界条件下，也分子动力学模拟，我们研究了分离过程中的N2和CO2在金星的背景下。我们的研究结果表明，分子扩散是非常低效的，和潜在的相分离是一个不太可能的机制。我们已经比较了所需的CO2的量，以形成所提出的梯度与什么可以从低火山活动的扩散脱气释放。所需的二氧化碳通量与在一些陆地火山系统上测量到的没有太大的不同，这表明金星上也有类似的作用。
Venus shares many similarities with the Earth, but concomitantly, some of its features are extremely original. This is especially true for its atmosphere, where high pressures and temperatures are found at the ground level. In these conditions, carbon dioxide, the main component of Venus’ atmosphere, is a supercritical fluid. The analysis of VeGa-2 probe data has revealed the high instability of the region located in the last few kilometers above the ground level. Recent works have suggested an explanation based on the existence of a vertical gradient of molecular nitrogen abundances, around 5 ppm per meter. Our goal was then to identify which physical processes could lead to the establishment of this intriguing nitrogen gradient, in the deep atmosphere of Venus. Using an appropriate equation of state for the binary mixture CO2–N2 under supercritical conditions, and also molecular dynamics simulations, we have investigated the separation processes of N2 and CO2 in the Venusian context. Our results show that molecular diffusion is strongly inefficient, and potential phase separation is an unlikely mechanism. We have compared the quantity of CO2 required to form the proposed gradient with what could be released by a diffuse degassing from a low volcanic activity. The needed fluxes of CO2 are not so different from what can be measured over some terrestrial volcanic systems, suggesting a similar effect at work on Venus.