Dike-Driven Hydrothermal Processes on Mars and Sill Emplacement on Europa
Craft, Kathleen Liana
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Evidence of hydrothermal and tectonic activity is found throughout our solar system. Here I investigated hydrothermal and fracturing processes on three planetary bodies: Earth, Mars and Europa. For the first project, we set up a dike-driven hydrothermal system and calculated heat and water flow using boundary layer theory. Water flow rates and volumes were then compared to the requirements for surface feature formation. Results found that the water volumes produced were adequate to form Athabasca Valles, except the flow rates were low. Episodic flood releases could enable the higher flow rates if water was first collected in aquifers, possibly stored beneath ice. On the icy moon Europa, I modeled a proposed sill emplacement mechanism using a finite element code and found that water could flow up through an approximately 10 km thick ice shell without freezing. The analysis also found that shallow cracks in the ice combined with deep cracks cause a stress direction change that helps the fracture turn and propagate more horizontally. However, the sill lifetime is less than the time a study by Dombard et al.  calculated to be necessary for the formation of flexure fractures along margins of double ridges. Replenishment processes will be explored in future work to help extend sill lifetime. The last investigation calculated dike induced permeability changes in the crust on Earth and Mars and related the changes to water and heat flow rates and water volumes. Comparisons were made to event plume heat and elevated fluid temperatures observed at mid-ocean ridges. Heat values determined by the models agreed well with the 10^14 to 10^17 J expected. For the Martian model, water flow rates and volumes were compared to formation requirements for the valley system Athabasca Valles. Results found that flow rates would be adequate in the high permeability damage zone adjacent to the dike. However, the lowered permeability outside the damage zone would restrict replenishment flow and could cause the need for water storage and periodic release between flood events as the volume within the damage zone is not adequate for the valley formation.
- Doctoral Dissertations