TY  - JOUR
A1  - Postberg, Frank
A1  - Kempf, Sascha
A1  - Schmidt, Jürgen
A1  - Brilliantov, Nikolai V.
A1  - Beinsen, Alexander
A1  - Abel, Bernd
A1  - Buck, Udo
A1  - Srama, Ralf
T1  - Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus
N2  - Saturn's moon Enceladus emits plumes of water vapour and ice particles from fractures near its south pole(1-5), suggesting the possibility of a subsurface ocean(5-7). These plume particles are the dominant source of Saturn's E ring(7,8). A previous in situ analysis(9) 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(9,10). It was not clear, however, whether the liquid is still present today or whether it has frozen. Here we report the identification of a population of E-ring grains that are rich in sodium salts (similar to 0.5- 2% by mass), which can arise only if the plumes originate from liquid water. The abundance of various salt components in these particles, as well as the inferred basic pH, exhibit a compelling similarity to the predicted composition of a subsurface Enceladus ocean in contact with its rock core(11). The plume vapour is expected to be free of atomic sodium. Thus, the absence of sodium from optical spectra(12) is in good agreement with our results. In the E ring the upper limit for spectroscopy(12) is insufficiently sensitive to detect the concentrations we found.
Y1  - 2009
UR  - http://www.nature.com/nature/
U6  - https://doi.org/10.1038/Nature08046
SN  - 0028-0836
ER  -