CRYOVOLCANIC EMPLACEMENT OF DOMES ON EUROPA

Many putative cryovolcanic features exist on the surface of Europa, and previous investigators have suggested that a subset of domes imaged by the Galileo spacecraft may be volcanic in origin. Assuming these domes were emplaced by viscous effusions of cryolava, models for the formation of volcanic domes on the terrestrial planets have been applied to the formation of cryovolcanic domes on Europa. Previous models applied to the emplacement of putative cryolava domes, which were initially developed for the formation of silicic domes on Earth and Venus, assumed a constant viscosity and, inter alia, non-physical singularities in the flow depth at the source of the eruption. Many of these shortcomings have been alleviated in our new modeling approach, which warrants a reassessment of the possibility of cryovolcanic domes on Europa.

Assuming a constant volume of cryolava has been rapidly emplaced onto the surface, we have investigated the formation of cryovolcanic domes on Europa, exploring the effect of boundary conditions on the solution of the Boussinesq equation for pressure driven fluid flow in a cylindrical geometry. Our new similarity solution eliminates singularities that were inherent in previous models and employs a viscosity that increases exponentially with time to account for cryolava cooling.

We have obtained axisymmetric profiles for dome height as a function of radial distance from the origin at multiple time steps. Our preliminary results show that at the onset of relaxation, bulk kinematic cryolava viscosities may be on the order of 10⁷ m²/sec, while the actual fluid lava viscosity within the dome may be much lower. The relaxation time to form the dome, which is linked to bulk cryolava rheology, is found to be approximately 3 years. Finally, cooling of the cryolava, while dominated by conduction through an icy skin, should not prevent fluids from advancing and relaxing to form domes within the allotted timescales. The next step of this work will be to apply this model to other putative cryovolcanic domes imaged by the Galileo spacecraft to constrain the range of emplacement times and eruption rates for this particular style of cryovolcanism on Europa.