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Nature. 2015 Mar 12;519(7542):207-10. doi: 10.1038/nature14262.

Ongoing hydrothermal activities within Enceladus.

Author information

1
Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado 80303, USA.
2
1] Institut für Geowissenschaften, Universität Heidelberg, 69120 Heidelberg, Germany [2] Institut für Raumfahrtsysteme, Universität Stuttgart, 70569 Stuttgart, Germany.
3
Department of Complexity Science and Engineering, University of Tokyo, Kashiwa 277-8561, Japan.
4
Laboratory of Ocean-Earth Life Evolution Research, JAMSTEC, Yokosuka 237-0061, Japan.
5
1] Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado 80303, USA [2] Institute for Particle and Nuclear Physics, Wigner RCP, 1121 Budapest, Hungary.
6
European Space Agency, ESAC, E-28691 Madrid, Spain.
7
Research and Development Center for Submarine Resources, JAMSTEC, Yokosuka 237-0061, Japan.
8
Graduate School of Environmental Studies, Tohoku University, Sendai 980-8579, Japan.
9
Department of Natural History Sciences, Hokkaido University, Sapporo 060-0810, Japan.
10
Graduate School of Environmental Sciences, Nagoya University, Nagoya 464-8601, Japan.
11
Institut für Raumfahrtsysteme, Universität Stuttgart, 70569 Stuttgart, Germany.

Abstract

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. 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. 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. Here we report an analysis of silicon-rich, nanometre-sized dust particles (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 °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.

PMID:
25762281
DOI:
10.1038/nature14262

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