Figure 4. Schematic illustration of hydrothermal circulations and the formation of silica on Enceladus.

(a) Deep hydrothermal circulation would have occurred between a warm, and probably porous5,6,7,45,70, rocky core and a cold ocean because of remnant heat from the early stages of Enceladus' evolution. (b) If heating has been induced by a recent heating event such as crustal overturn41, orbital evolution42 or an impact43, hydrothermal reactions would have taken place at the ocean–rock interface. In this case, serpentinization and its associated heat production may have been important in sustaining high-temperature water–rock interactions.