标题： 金属性气体分馏预测用于金星上层大气的高速采样 显示英文标题

标题： Noble Gas Fractionation Predictions for High Speed Sampling in the Upper Atmosphere of Venus

摘要： 金星，我们的邻近行星，是一个露天实验室，可用于研究为什么地球和金星以如此不同的方式演化。 行星大气中的惰性气体是其地质物理演化的示踪剂，测量金星大气中惰性气体的元素和同位素组成，可以告诉我们整个行星的起源和演化。 在本工作中，我们描述了一种新的小型卫星任务概念，金星大气采样返回（VATMOS-SR），该任务将从金星高层大气中带回气体样本到地球进行科学分析。 为了确保能够将采样气体的组成（当航天器以超过10公里/秒的速度飞行时采集）与自由流大气组成相关联，采用了大规模数值模拟来模拟流入和通过采样系统的流动。 重点是量化在采样和传输过程中发生的惰性气体元素和同位素分馏，以确定样品中测得的惰性气体同位素比值与金星大气中实际同位素比值的比较。 我们发现，与自由流条件相比，较轻的惰性气体在采样后被耗尽，而较重的则被富集，这是由于流动场中存在的高压梯度。 最后，我们观察到，一般来说，数值参数对观察到的分馏没有重大影响。 然而，自由流速度和密度对分馏有重大影响，需要精确知道以正确重建采样系统中的分馏。 我们证明，可以通过数值模拟预测样品分馏，并认为VATMOS-SR，这可能是第一个从另一颗行星带回样本的任务，可以回答有关理解金星演化的关键科学问题。 显示英文摘要

摘要： Venus, our neighboring planet, is an open-air laboratory that can be used to study why Earth and Venus evolved in such different ways. Noble gases in planetary atmospheres are tracers of their geophysical evolution, and measuring the elemental and isotopic composition of noble gases in the Venus atmosphere informs us about the origin and evolution of the entire planet. In this work we describe a new SmallSat mission concept, Venus ATMOSpheric - Sample Return (VATMOS-SR), that would return gas samples from the upper atmosphere of Venus to Earth for scientific analysis. To ensure it is possible to relate the composition of the sampled gases (acquired when the spacecraft is traveling >10 km/s) to the free stream atmospheric composition, large-scale numerical simulations are employed to model the flow into and through the sampling system. An emphasis is placed on quantifying noble gas elemental and isotopic fractionation that occurs during the sample acquisition and transfer process, to determine how measured isotopic ratios of noble gases in the sample would compare to the actual isotopic ratios in the Venusian atmosphere. We find that lighter noble gases are depleted after they are sampled compared to the freestream conditions, and heavier ones are enriched, due to the high pressure gradients present in the flowfield. Finally, we observe that, in general, the numerical parameters do not have a major impact on the observed fractionation. However, the freestream velocity and density have a major impact on fractionation and need to be precisely known to properly reconstruct the fractionation in the sampling system. We demonstrate that the sample fractionation can be predicted with numerical simulations, and believe that VATMOS-SR, which could be the first mission to bring back samples from another planet, could answer key scientific questions related to understanding the evolution of Venus.