Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus

@article{Postberg2009SodiumSI,
  title={Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus},
  author={Frank Postberg and Sascha Kempf and J{\"u}rgen Schmidt and Nikolai V. Brilliantov and Alexander Beinsen and Bernd Abel and Udo Buck and Ralf Srama},
  journal={Nature},
  year={2009},
  volume={459},
  pages={1098-1101}
}
Saturn's moon Enceladus emits plumes of water vapour and ice particles from fractures near its south pole, suggesting the possibility of a subsurface ocean. These plume particles are the dominant source of Saturn’s E ring. A previous in situ analysis of these particles concluded that the minor organic or siliceous components, identified in many ice grains, could be evidence for interaction between Enceladus’ rocky core and liquid water. It was not clear, however, whether the liquid is still… 
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References

SHOWING 1-10 OF 31 REFERENCES
No sodium in the vapour plumes of Enceladus
TLDR
A ground-based spectroscopic search for atomic sodium near Enceladus places an upper limit on the mixing ratio in the vapour plumes orders of magnitude below the expected ocean salinity.
An oceanic composition on early and today's Enceladus
The oceanic composition on Saturn's moon Enceladus is evaluated through calculations of thermochemical equilibria at hydrothermal and freezing settings. Conditions of rock alteration are constrained
Slow dust in Enceladus' plume from condensation and wall collisions in tiger stripe fractures
TLDR
It is shown that repeated wall collisions of grains, with re-acceleration by the gas, induce an effective friction, offering a natural explanation for the reduced grain velocity, and suggests liquid water below Enceladus’ south pole.
Shear heating as the origin of the plumes and heat flux on Enceladus
TLDR
It is shown that the most likely explanation for the heat and vapour production is shear heating by tidally driven lateral (strike-slip) fault motion with displacement of ∼0.5 m over a tidal period, suggesting that the ice shell is decoupled from the silicate interior by a subsurface ocean.
A Clathrate Reservoir Hypothesis for Enceladus' South Polar Plume
We hypothesize that active tectonic processes in the south polar terrain of Enceladus, the 500-kilometer-diameter moon of Saturn, are creating fractures that cause degassing of a clathrate reservoir
Cassini Encounters Enceladus: Background and the Discovery of a South Polar Hot Spot
TLDR
Cassini's Composite Infrared Spectrometer (CIRS) detected 3 to 7 gigawatts of thermal emission from the south polar troughs at temperatures up to 145 kelvin or higher, making Enceladus only the third known solid planetary body—after Earth and Io—that is sufficiently geologically active for its internal heat to be detected by remote sensing.
The possible origin and persistence of life on Enceladus and detection of biomarkers in the plume.
TLDR
The jets of icy particles and water vapor issuing from the south pole of Enceladus are evidence for activity driven by some geophysical energy source, and it is possible that a liquid water environment exists beneath the south polar cap, which may be conducive to life.
Cassini Observes the Active South Pole of Enceladus
TLDR
The shape of Enceladus suggests a possible intense heating epoch in the past by capture into a 1:4 secondary spin/orbit resonance.
Cassini Ion and Neutral Mass Spectrometer: Enceladus Plume Composition and Structure
TLDR
INMS data indicate that the atmospheric plume and coma are dominated by water, with significant amounts of carbon dioxide, an unidentified species with a mass-to-charge ratio of 28 daltons (either carbon monoxide or molecular nitrogen), and methane.
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