Abstract
Water-rich plumes with sodium salts erupting from warm fractures near the south pole of Saturn's icy moon Enceladus suggest the presence of a liquid-water reservoir in the interior. The findings of silica nanoparticles in Saturn's E-ring derived from the plumes imply active geochemistry involving water-rock interactions. It is however highly unknown the particular conditions of temperature, pH, and mineral compositions that can sustain the formation of silica in Enceladus. Here we report laboratory experiments and calculation of hydrothermal reactions simulating Enceladus' interior. To achieve high silica concentrations in the fluids, hydrous silicates of Enceladus' core would be composed mainly of serpentine and saponite (or talc at higher temperatures), consistent with chondritic compositions of its rocky core. To form silica nanoparticles in Enceladus, the fluid temperature needs to reach ? 150?200°C, suggesting extensive hydrothermal activity. These results support the idea that deep hydrothermal circulation in a warm core drives hotspots in the H2O mantle, possibly causing large tidal dissipation and internal melting.
