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Laboratory Friction Experiments: Shear Heating and the Seismogenic Zone on Icy Satellite Faults
We performed friction experiments with water ice and ice+ammonia mixtures at icy satellite conditions to better understand the frictional behavior of icy satellite faults. We observed a temperature dependence on the coefficient of friction and explored the effect of partial melt, which may inform heat generation rates in shear heating models of icy faults. We've also mapped out a temperature dependent seismogenic zone in an ice shell based on the rate-state formulation for friction. Published results of this work can be found here. We are currently exploring the tidal effects on the frictional behavior of icy satellite faults through the results of our oscillatory loading friction experiments.
Running an ice-on-ice friction experiment with our liquid nitrogen-cooled and servo-hydraulically controlled biaxial deformation apparatus.
Laboratory Melt Experiments: Melt Transport Rates Under Icy Satellite Faults
Funded by the Future Investigators in NASA Earth and Space Science Technology (FINESST) award, we are conducting laboratory experiments to measure the bulk viscosity, permeability, and capillarity of partially molten ice mixtures. Using these parameters we will model melt migration under strike-slip faults on Europa to better estimate melt transport rates and the stability of melt ponds in the ice shell. To measure bulk viscosity, we are compacting ice+ammonia mixtures at a range of temperatures, grain sizes, and partial melt fractions in a uniaxial pressure cell. To constrain permeability and capillarity, we will measure the amount of melt infiltration from an ice+ammonia sample to a pure ice sample without uniaxial stress through microstructural characterization.
Left to right: image and schematic of the uniaxial pressure cell, sample setup to measure capillary infiltration with no stress (a), and sample setup to measure bulk viscosity by compaction (b).
Identifying the Feasibility and Limits of Subduction on Europa
Subduction, if present on Europa, could be a potentially significant transport mechanism for material through the ice shell. Improving upon work by Howell & Pappalardo (2019), we are are re-working the force balance framework of subduction to incorporate more realistic rheological and frictional behaviors on an ice shell based on laboratory experiments. We are exploring the conditions under which subduction may be possible and estimating potential oxidant transport rates from subduction.
"Subsumption" of cold, brittle ice into a warmer, ductile ice layer (Kattenhorn & Prockter, 2014).
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