Enceladus' Icy Plume - The E-Ring Cradle

在2005年三次飞越土卫二期间，卡西尼号探测器发现了一个巨大的气尘羽流，它来自南极一个地质上年轻、伤痕累累、非常温暖的地区。这一独特的探测清楚地表明，土星的E环是在地球物理活跃的南极的小冰世界土卫二的种子。在这个项目中，我们计划开发一个模型的E环粒子的起源与目标，以获得速度和冰粒的大小分布。其基本思想包括冰粒在土卫二南极冰壳的地下通道或裂缝中的水蒸气中的成核、生长和加速。这些研究将包括固体冰粒稳定出现的过饱和气体通道流动的热力学和流体力学/动力学。为了再现所观察到的尘埃羽流的性质，该模型必须包括允许羽流颗粒减速的过程，如与通道壁的碰撞。发射粒子的速度和大小的分布将决定土卫二的羽流的属性，并最终随后的动态和外观的土星E环。与卡西尼日期的尘埃羽流和E环的建模和分析之间的迭代方法，我们试图获得新的见解，在地下通道地质和流动动力学，否则仍然隐藏在南极冰。此外，我们预计，我们的建模预测将是至关重要的利益，规划即将到来的近距离飞越的卡西尼号航天器的土卫二在2008年及以后。

During three flybys of Enceladus in 2005 the Cassini-spacecraft spotted a gigantic gas-dust plume emanating from a geologically young, scarred and remarkably warm region at the south pole. This unique detection made clear that the Saturn's E ring is seeded in the geo-physically active south pole of the small icy world Enceladus.In this project we plan to develop a model of the origin of the E ring particles with the goal to derive the velocity and the size distribution of the icy grains. The basic ideas include nucleation, growth and acceleration of icy motes in the water vapor in underground channels or cracks perforating the south-polar ice-shell of Enceladus. The studies will incorporate the thermo - and hydrodynamics/kinetics of the channel-flow of the supersaturated gas from where solid ice particles steadily emerge. In order to reproduce the properties of the observed dust plume, the model must include processes which allow for a deceleration of the plume-grains like collisions with the channel walls. The resulting distributions of velocities and sizes of the launched particles will determine the properties of Enceladus' plume and eventually the subsequent dynamics and appearance of the E ring of Saturn.With an iterative approach between modeling and analysis of the Cassini-date of the dust plume and the E ring we try to gain new insights in the underground channel-geology and flow dynamics which otherwise remained hidden by the south-polar ice. Furthermore, we expect that predictions of our modeling will be of vital interest for the planning of the upcoming close flybys of the Cassini spacecraft of Enceladus in 2008 and later.