Characterizing the Icy H2O-MgSO4 Eutectic System: Preliminary Results on Microstructure and Mechanical Properties

A columnar multiphase ice-rich system, with column diameter of 1-2 mm, has been produced through unidirectional solidification of the H₂O-MgSO₄ eutectic solution and was characterized using thin sections and scanning electron microscopy (SEM). Phases have been identified using electron dispersion spectroscopy (EDS). Elastic properties were determined using acoustic emission and the ductile-brittle transition was determined from uniaxial compression. Measurements of fracture toughness, by three point bending at -10 ^oC, indicate the columnar eutectic material is ~1.3 times tougher than freshwater columnar ice, while cantilever bending tests at -10 ^oC indicate the eutectic system is ~1.6 times stronger. Measurements of the kinetic coefficient of friction, by double shear sliding at temperatures of -10 ^oC and -175 ^oC, indicate that friction for the eutectic system is ~1.6 times larger compared to freshwater columnar ice. These initial results are of importance in modeling the behavior of extraterrestrial icy material, with particular attention to Europa and the possibility of a subsurface ocean.