Hydrothermal Activity in the Solar System's Ocean Worlds

Evidence from spacecraft data indicates hydrothermal activity in many places in the solar system, most compellingly in the planet Mars and Saturn's moon Enceladus. The current understanding of the duration, extent, and underlying geochemistry of this hydrothermalism is poorly constrained. In the solar system's extant ocean worlds—Europa, Ganymede, Callisto, Enceladus, Titan, and possibly also Triton and Pluto—the potential for continued hydrothermal circulation and water-rock chemistry creates the prospect for long-term redox disequilibria that might provide the energy needed for life. However, in the absence of large-scale tectonic activity, the available supply of rocky substrate must be determined when the planet or moon forms, and the extent of reaction must be limited by the depths to which fluids can percolate into the rock (Vance et al. 2016). Geophysical forward modeling, incorporating improved geochemical data, provides a way to constrain possible paths in the geochemical evolution of potentially habitable worlds, and the consequent chemical and geophysical signatures of those different paths that might be measured by planned spacecraft missions (Vance et al. 2018).

Vance, S. D. et al. (2016). Geophysical controls of chemical disequilibria in Europa. Geophysical Research Letters, 43(10):4871-4879.

Vance, S. D. et al. (2018). Geophysical investigations of habitability in ice-covered ocean worlds. Journal of Geophysical Research: Planets, 123, 180-205.