Between 2004 and 2007 the instruments of the CASSINI spacecraft discovered hydrocarbon lakes in the polar regions of Titan. We have developed a lake-atmosphere equilibrium model allowing the determination of the chemical composition of these liquid areas. The model is based on uncertain thermodynamic data and precipitation rates of organic species predicted to be present in the lakes and seas that are subject to spatial and temporal variations. Here we explore and discuss the influence of these uncertainties and variations. The errors and uncertainties relevant to thermodynamic data are simulated via Monte-Carlo simulations. Global Circulation Models (GCM) are also employed in order to investigate the possibility of chemical asymmetry between the south and the north poles, due to differences in precipitation rates. We find that mole fractions of compounds in the liquid phase have a high sensitivity to thermodynamic data used as inputs, in particular molar volumes and enthalpies of vaporization. When we combine all considered uncertainties, the ranges of obtained mole fractions are rather large (up to ~8500%) but the distributions of values are narrow. The relative standard deviations remain between 10% and ~300% depending on the compound considered. Compared to other sources of uncertainties and variability, deviation caused by surface pressure variations are clearly negligible, remaining of the order of a few percent up to ~20%. Moreover no significant difference is found between the composition of lakes located in north and south poles. Because the theory of regular solutions employed here is sensitive to thermodynamic data and is not suitable for polar molecules such as HCN and CH3CN, our work strongly underlines the need for experimental simulations and the improvement of Titan's atmospheric models.
Air-Sea Interactions on Titan: Lake Evaporation, Atmospheric Circulation, and Cloud Formation
泰坦丰富的湖泊和海洋通过一种通常被称为空气-海洋相互作用的过程与大气交换甲烷蒸汽和能量。这种湍流交换过程的研究与大气中尺度模式耦合到一个平板模式表示下垫面湖泊。通过几十个二维数值模拟，研究了湖泊尺度、有效湖混合层深度、背景风速、气湖温差和大气湿度对海气相互作用过程的影响。一般的，准稳定的解决方案是一个非常弱的背景羽流环流驱动的浮力蒸发的甲烷与一个强大的相反的热直接（海风）环流驱动的湖泊和温暖的内陆空气之间的热对比的非线性叠加。具体的解决方案取决于所选择的大气和湖泊属性参数的值，但这两个环流的叠加的一般解决方案是持久的。与前人的分析工作相一致，感热通量和潜热通量趋向于相反和相等的值，使得它们的比值Bowen比在大多数（但不是全部）准稳态解中接近-1.0。重要的是，在几乎所有的情况下，通量的绝对星等的趋势非常小的值，这样的平衡解决方案也几乎是一个平凡的解决方案，其中海气能量交换约3 W m-2或less. In所有情况下，一个凉爽，潮湿，静态稳定的浅海层，近平静的风和小湍流通量交换与一个较冷的底层湖泊产生的模型。湖泊的温度、空气的海洋属性和海风的强度取决于初始条件，在较小程度上取决于边界条件。
Science goals and new mission concepts for future exploration of Titan's atmosphere geology and habitability: Titan POlar Scout/orbitEr and In situ lake lander and DrONe explorer (POSEIDON)
为了响应ESA Voyage 2050宣布的机会，我们提出了一项雄心勃勃的L级任务，以探索太阳系中最令人兴奋的天体之一，土星最大的卫星泰坦。泰坦是一个“两洋世界”，是一个富含有机物的天体，其走廊-表面-大气层的相互作用在复杂性上与地球相当。土卫六也是太阳系中少数几个具有可居住潜力的地方之一。土卫六非凡的性质只是部分揭示了卡西尼-惠更斯任务，仍然持有的奥秘，需要使用各种车辆和仪器进行全面探索。拟议的飞行任务概念POSEIDON（Titan Polar Scout/orbitEr and In situ lake lander Drone explorer）将对Titan进行联合轨道和现场调查。其目的是在卡西尼-惠更斯号探测器的范围和科学/技术成就的基础上再接再厉，以以前不可能的方式探索土卫六，特别是通过长时间的全特写和现场覆盖。在拟议的飞行任务结构中，海神号由两个主要部分组成：一个航天器，带有一套大型仪器，将围绕土卫六运行，最好是在低偏心率的极地轨道上运行;一套现场调查组件，即一个湖泊着陆器、一架“重型”无人驾驶飞机（可能是水陆两用的）和/或一队小型无人驾驶飞机，专门用于探索极地地区。理想的到达泰坦的时间应该是在下一个北方的春分（2039年）之前，因为春分是监测大气和地表季节变化的最活跃时期。用轨道飞行器和现场元件探索土卫六北纬度将与即将进行的美国航天局新边疆蜻蜓飞行任务高度互补，该…
