Souček Ondřej, Běhounková Marie, Lanzendörfer Martin, Tobie Gabriel, Choblet Gaël
Mathematical Institute, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic.
Department of Geophysics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic.
Nat Commun. 2024 Aug 28;15(1):7405. doi: 10.1038/s41467-024-51677-z.
After discovering a jet activity near the south pole of Saturn's moon Enceladus, the Cassini mission demonstrated the existence of a subsurface water ocean with a unique sampling opportunity through flybys. Diurnal variations in the observed brightness of the plume suggest a tidal control, although the existence and timing of two activity maxima seem to contradict stress analysis predictions. Here, we re-interpret the observed plume variability by combining a 3D global model of tidal deformation of the fractured ice shell with a 1D local model of transport processes within south-polar faults. Our model successfully predicts the observed plume's temporal variability by combining two independent vapour transport mechanisms: slip-controlled jet flow and normal-stress-controlled ambient flow. Moreover, it provides a possible explanation for the differences between the vapour and solid emission rates during the diurnal cycle and the observed fractionation of the various icy particle families. Our model prediction could be tested by future JWST observations targeted when Enceladus is at different positions on its orbit and could be used to determine the optimal strategy for plume material sampling by future space missions.
在发现土星卫星土卫二南极附近存在喷流活动后，卡西尼号任务通过多次飞掠展示了地下存在水海洋，并提供了独特的采样机会。羽流观测亮度的昼夜变化表明存在潮汐控制，尽管两个活动最大值的存在和时间似乎与应力分析预测相矛盾。在这里，我们通过将破裂冰壳潮汐变形的三维全球模型与南极断层内输运过程的一维局部模型相结合，重新解释观测到的羽流变化。我们的模型通过结合两种独立的蒸汽输运机制成功预测了观测到的羽流时间变化：滑移控制的喷流和正应力控制的环境流。此外，它还为昼夜循环中蒸汽和固体排放率的差异以及观测到的各种冰粒家族的分馏提供了一种可能的解释。我们的模型预测可以通过未来詹姆斯·韦布空间望远镜（JWST）在土卫二处于其轨道不同位置时进行的观测来检验，并可用于确定未来太空任务采集羽流物质的最佳策略。
