The discovery of water vapour and ice particles erupting from Saturn's moon Enceladus fuelled speculation that an internal ocean was the source. The presence of sodium chloride is expected in a long-lived ocean in contact with a rocky core; however, a ground-based spectroscopic search for atomic sodium near Enceladus now places an upper limit on the mixing ratio in the vapour plumes orders of magnitude below expected ocean salinity. These observations are consistent with a variety of alternative eruption sources including a deep ocean, a freshwater reservoir, or ice.
- Nicholas M. Schneider
- Matthew H. Burger
- Nicholas A. Achilleos
