Deep Ice Formation in Convecting Ice-Ocean Systems: Implications for Trace Element Transport from Europa's Ocean to its Surface
Abstract
Outer planetary missions and telescopic discoveries, together with theoretical predictions, have identified a plethora of potential astrobiological candidates that possess diverse signatures such as liquid water, chemical circulation, mineral assemblages and optimal temperatures that may have or still favor biological life. Europa with its deformed surface, an ice shell with a putative subsurface liquid water ocean and an induced magnetic signal still presents one of the accessible targets of astrobiological exploration. Of critical interest is whether chemistry of the subsurface liquid water ocean can be transported to the surface to be detected by future missions. We hypothesize that for a convecting ice shell, the ice-ocean boundary involves melting in downwelling regions and freezing in upwelling regions. New ice formed by freezing at the phase change boundary could reflect the capture of trace elements from the fluid layer below and thus the study of its propagation can provide interesting speculations on transport of trace species from the ocean to the surface. We have initiated a study of the two phase convective system in order to understand the effects of the phase boundary between the solid and liquid components. First, we have established a solid ice-proxy fluid system that is a convenient approximation of the real system. This is achieved by employing a proxy fluid whose viscosity is higher than that of liquid water yet remains orders of magnitude smaller than that of ice viscosity. We have demonstrated that this approximation sufficiently decouples the convective dynamics of the solid and fluid layers with little variation on further decrease of the fluid viscosity. The numerical models employ tracers to track the new ice and the fractional density of the new ice is mapped throughout the shell. We then proceed to analyze the formation of new ice at the transition interface and its transport by solid state convection in the ice shell. The tracer density fraction estimates the relative concentration of the new ice in different regions of the warm ice plumes at each time step. We present preliminary results which demonstrate that entrainment of new ice into diapirs occurs at the interface. This new ice further traces the convection patterns within the shell. These calculations aim to study the rate of formation of new ice, and to investigate the potential pathways of new ice through the shell i.e. whether it is possible for the warm upwelling ice to deform or break the cold ice lid above.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.P54A..05A
- Keywords:
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- 6221 PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS Europa;
- 5422 PLANETARY SCIENCES: SOLID SURFACE PLANETS Ices;
- 5200 PLANETARY SCIENCES: ASTROBIOLOGY