Tensile strength and elastic properties of fine-grained ice aggregates: Implications for crater formation on small icy bodies

Abstract

The mechanical and elastic properties of ice aggregates are important in the physics of avalanches and crater formation on icy bodies, such as icy satellites and cometary nuclei. Here we conducted uniaxial tensile tests and elastic-wave velocity measurements on artificial fine-grained ice aggregates (snow) to infer the potential for crater formation on small icy bodies. The uniaxial tensile tests on the artificial snow with filling factors (f) in the 0.30–0.59 range at −15 °C demonstrate that the tensile strength (Yt) depends on its filling factor; we obtained the empirical equation Yt=103.5f3.5 (in kPa) based on our results, which is consistent with the upper limit of natural snow’s tensile strength. The compressional- and shear-wave velocities of artificial snow with f≥ 0.4 were measured via the ultrasonic pulse velocity method. The elastic-wave velocities decrease linearly with decreasing f values. Our calculations for the Young’s moduli of the artificial snow from the elastic-wave velocity measurements are 10–40 times higher than those from the tensile tests, which indicate the rate-dependent properties of the fine-grained ice aggregates. We propose a tensile strength estimation of a cometary surface via an artificial impact based on our results and a crater-scaling law in the strength-dominated regime.