Stressed and sliding ice surfaces liquefy without much heating

The low kinetic friction observed between ice or snow and numerous counterbodies is commonly attributed to a thin interfacial water layer 1-3, which is believed to exist because of pressure melting 4, surface melting 5, 6, or friction-induced heating 7. However, even the currently leading theory of frictional melting keeps being challenged, for example, due to the lack of detectable warming of snow surfaces under a rotating slider at -7C temperature and 1 m/s sliding velocity despite high temporospatial resolution 8. Here we present molecular simulations of ice interfaces that reveal that ice surfaces liquefy readily without melting thermally but rather by displacement driven amorphization, normal-stress gradients, and tensile in-plane stress. Yet, friction coefficients below 0. 01, as observed during the sliding of hydrophobic solids over ice 9, appear possible only when the counterfaces are smooth and allow water to slip past them. Our findings provide fundamental guidelines on how to optimize ice friction and challenge experimentalists to measure the surface temperature of ice and snow at minute scales and with unprecedented speed.