Hydrothermal processes on Enceladus Saturn's moon Enceladus has a subsurface ocean covered by a layer of ice. Some liquid escapes into space through cracks in the ice, which is the source of one of Saturn's rings. In October 2015, the Cassini spacecraft flew directly through the plume of escaping material and sampled its chemical composition. Waite et al. found that the plume contains molecular hydrogen, H2, a sign that the water in Enceladus' ocean is reacting with rocks through hydrothermal processes (see the Perspective by Seewald). This drives the ocean out of chemical equilibrium, in a similar way to water around Earth's hydrothermal vents, potentially providing a source of chemical energy. Science, this issue p. 155; see also p. 132 Enceladus’ subsurface ocean contains H2, a sign of hydrothermal reactions between rock and water. Saturn’s moon Enceladus has an ice-covered ocean; a plume of material erupts from cracks in the ice. The plume contains chemical signatures of water-rock interaction between the ocean and a rocky core. We used the Ion Neutral Mass Spectrometer onboard the Cassini spacecraft to detect molecular hydrogen in the plume. By using the instrument’s open-source mode, background processes of hydrogen production in the instrument were minimized and quantified, enabling the identification of a statistically significant signal of hydrogen native to Enceladus. We find that the most plausible source of this hydrogen is ongoing hydrothermal reactions of rock containing reduced minerals and organic materials. The relatively high hydrogen abundance in the plume signals thermodynamic disequilibrium that favors the formation of methane from CO2 in Enceladus’ ocean.

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卡西尼号在土卫二羽流中发现分子氢：热液过程的证据

土卫二的热液过程 土卫二的卫星土卫二有一个被一层冰覆盖的地下海洋。一些液体通过冰裂缝逃逸到太空，这是土星环之一的来源。2015 年 10 月，卡西尼号宇宙飞船直接飞越了逃逸物质的羽流，并对其化学成分进行了采样。韦特等人。发现羽流中含有分子氢 H2，这是土卫二海洋中的水通过热液过程与岩石发生反应的迹象（参见 Seewald 的观点）。这使海洋脱离化学平衡，类似于地球热液喷口周围的水，可能提供化学能源。科学，这个问题 p。155; 另见第。132 土卫二的地下海洋含有 H2，岩石和水之间热液反应的标志。土星的卫星土卫二有一片冰雪覆盖的海洋；一股物质从冰的裂缝中喷涌而出。羽流包含海洋和岩石核心之间水岩相互作用的化学特征。我们使用卡西尼号飞船上的离子中性质谱仪检测羽流中的分子氢。通过使用仪器的开源模式，仪器中氢气生产的背景过程被最小化和量化，从而能够识别土卫二原生氢的具有统计意义的信号。我们发现这种氢的最可能来源是含有还原矿物和有机材料的岩石正在进行的热液反应。