Impact and friction mechanisms and structural changes of snow and ice in snow avalanches, ice blasts and icy planetecimal impacts

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Ice-ice friction measurements were extended to the lowest sliding velocities aimed originally in the project. For the experiment a new device of non-rotation type was constructed and installed in a cold room, which enabled us to carry out the friction experiment to the velocities of 10^<-7> to 10^<-3> m/s and normal stresses of 123 to 368 kPa. The obtained results below 10^<-4> m/s was different f rom what has been expected from the traditional adhesion shear mechanism. Based on the experiment al result a new model of adhesion shear mechanism was proposed taking account of junction growth d ue to sintering of ice asperities on the sliding surfaces.High speed impact experiments were conducted in relation to the formation mechanism of characteristic craters found on regolith layers on asteroids, Mars, and other icy bodies. Samples used are mixtures of H_2O ice, CO_2 ice and rocks, and projectiles, made of H_2O ice, metal or plastic, were impacted with a speed of 100 to 600 m/s. The project was conducted with cooperation of Prof. Leliwa-Kopystysnski of Warsaw University. Effects of electric field on ice friction were investigated.