Seminar: Little to No Active Faulting Likely at Europa’s Seafloor Today

Many of the outer Solar System’s icy satellites feature known or suspected subsurface oceans, at least some of which are likely situated atop rocky interiors. Water–rock interactions at and beneath these seafloors might support chemoautotrophic habitats there, sustained by hydrothermal systems and perhaps even ongoing seafloor volcanism. Any attainment of chemical equilibrium between the seafloor and ocean might limit the availability of chemical energy for life, however. In this talk, I review how we have characterised the stress state of Europa’s seafloor, and thus the prospect for fracturing and associated sub-seafloor fluid flow. We consider stresses from tidal forcing, global contraction, mantle convection, and serpentinisation, and find that none of these mechanisms is likely able to drive slip along even pre-existing fractures in the present. Ocean water–rock reactions taking place beneath the seafloor today are therefore probably restricted to fluid flow through only the upper few hundred metres of the seafloor. Any processes able to sustain habitable conditions at the Europan seafloor in the present are most likely independent of ongoing tectonic activity.