| Abstract | High-speed imaging (30,000 images/s has been used to observe the behavior of freshwater ice during crushing at –10°C. The ice contact zone consisted of an intact high-pressure central area surrounded by pulverized spall debris and partially refrozen melt. The removal of ice from the intact ice zone occurred through the viscous radial flow of a pressurized thin layer of melt. A sawtooth pattern was evident in the load record, due to spalling behavior. The movement of the platen and ice towards each other was intermittent, that is, slow on the ascending side of a sawtooth and very rapid on the descending side. Liquid was produced at the platen/ice interface during both the slow and rapid movements and was observed to create rapidly moving jets of ice and liquid (up to 40 m/s) emanating from the periphery of the contact zone during the load drops. The Saturnian moon Enceladus is an intriguing body consisting largely of water ice that exhibits great tectonic behavior in some areas, known as tiger stripes, and has been observed to eject plumes of water vapour and ice crystals from faults in these regions. The ice crushing mechanisms described here could occur when warm ice prominences, on opposing walls of open fissures in the upper regions of faults, crush against each other during the interfacial sliding events that are known to occur throughout the diurnal tidal stress cycle. This may contribute to the plumes through generation of liquid and warm ice that act as sources of water vapour that escapes from the moon. Furthermore, the liquid/solid ejecta itself may be jettisoned directly out of the fissures, upwards from the moon’s surface to significant altitude, possibly even at escape velocity. Some ice-ice interaction scenarios at the sliding ice interfaces of faults in the tiger stripes region are proposed that may generate ice crushing conditions similar to those in the experiments reported here. |
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