Liquid processes within icy world cryospheres: Insights from experimental and natural analogues

The cryospheres of ice-covered ocean worlds (i.e., their surfaces and solid ice layers) represent a new frontier in our understanding of the functioning and evolution of planetary systems. Cryospheres govern ocean-surface interaction and play active roles in the evolution and habitability of icy worlds. Furthermore, icy world cryospheres show evidence for a fascinating spectrum of geological activity that is unique to this class of world. Dynamic processes such as ‘cryovolcanic’ plumes or brine extrusions offer immense promise for exploration, as they may transport liquids from the subsurface to the surface environment where they can be studied by spacecraft. Indeed, salts and other endogenic materials have been detected at the surfaces of Enceladus, Europa, Ganymede and Ceres, indicating that some ocean to surface transport takes place. However, interpreting the archive of ocean chemistry recorded at icy world surfaces requires accounting for how the composition of ocean materials is influenced by cryosphere processes. Many of these processes have no direct analogy in silicate rocky planetary systems, meaning new frameworks are required. This challenge can be met by integrating studies of Earth’s cryosphere with laboratory simulations.

I will present results from studies of experimental and natural analogues that provide insight into the potential chemical diversity generated by dynamic processes in icy world cryospheres. I will show how permafrost-hosted brine seeps in the High Arctic can help us understand how ocean composition and evidence of habitability could be transported and altered by ice-hosted brines. I will describe laboratory investigations into how salts emplaced from subsurface fluids can influence long-term evolution of icy world surface features. Finally, I will highlight recent laboratory discoveries of novel hydrates that show how the thermal history of frozen fluids can be recorded in their mineralogical composition. Together, this work provides new frameworks for interpreting surface composition of icy worlds that can be used by upcoming missions such as NASA's Europa Clipper and ESA's JUICE to identify regions of recent fluid delivery to the surfaces of icy worlds.