Ongoing hydrothermal activities within Enceladus
Ongoing hydrothermal activities within Enceladus
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DOI：
10.1038/nature14262
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发表时间：
2015-03-12
期刊：
影响因子：
64.8
通讯作者：
Srama, Ralf
中科院分区：
文献类型：
--
作者：
Hsu, Hsiang-Wen;Postberg, Frank;Srama, Ralf
从土星卫星土卫二的羽流中发出的富含钠盐的冰粒的检测表明，这些冰粒是从液态水水库中形成的冻结液滴，该水库是或已经与岩石接触（1，2）。重力场测量表明，在30至40公里厚的冰壳之下存在着一个约10公里厚的区域性南极地下海洋（3）。这些发现意味着土卫二核心周围地区的岩石-水相互作用。由此产生的化学“足迹”预计将被保存在液体中，随后向上传输到近地表羽流源，在那里它们最终将被喷射出来，并可由航天器测量（4）。在这里，我们报告了对富含硅的纳米级尘埃颗粒（5-8）（所谓的流颗粒）的分析，这些颗粒从土星的水冰主导的物体中脱颖而出。我们将这些颗粒解释为纳米级的SiO2（二氧化硅）颗粒，最初嵌入在土卫二地下沃茨中散发出的冰粒中，并通过土星E环的溅射侵蚀释放出来。流粒子的组成和有限的大小范围（半径2至8纳米）表明，与全球规模的地热活动有关的高温（>90摄氏度）热液反应正在进行，这种地热活动将热液产物从至少40公里深的海底迅速输送到土卫二的羽流。
Detection of sodium-salt-rich ice grains emitted from the plume of the Saturnian moon Enceladus suggests that the grains formed as frozen droplets from a liquid water reservoir that is, or has been, in contact with rock(1,2). Gravitational field measurements suggest a regional south polar subsurface ocean of about 10 kilometres thickness located beneath an ice crust 30 to 40 kilometres thick(3). These findings imply rock-water interactions in regions surrounding the core of Enceladus. The resulting chemical 'footprints' are expected to be preserved in the liquid and subsequently transported upwards to the near-surface plume sources, where they eventually would be ejected and could be measured by a spacecraft(4). Here we report an analysis of silicon-rich, nanometre-sized dust particles(5-8) (so-called stream particles) that stand out from the water-ice-dominated objects characteristic of Saturn. We interpret these grains as nanometre-sized SiO2 (silica) particles, initially embedded in icy grains emitted from Enceladus' subsurface waters and released by sputter erosion in Saturn's E ring. The composition and the limited size range (2 to 8 nanometres in radius) of stream particles indicate ongoing high-temperature (>90 degrees C) hydrothermal reactions associated with global-scale geothermal activity that quickly transports hydrothermal products from the ocean floor at a depth of at least 40 kilometres up to the plume of Enceladus.