Modeling and Simulation of Planetary Porous Ice Analogs

Abstract:

In recent years, there has been a growing interest in the robotic exploration of icy bodies that have shown particularly favorable conditions for the emergence of life, like Enceladus and Europa. One of the main challenges for the design and control of planetary robotic exploration systems is the lack of information about the surface mechanical behavior. To date, only remote sensing data is available, which only loosely constrains the properties of the surface. To better characterize the surface mechanical behavior and enable the simulation of robot-terrain interactions, a numerical model of the terrain is needed. In this work, we present a physics-based numerical mechanical model of icy surfaces that explicitly represents the microstructure and its evolution upon sintering. The model is based on the Discrete Element Method with frictional and cohesive intergranular interactions. The model dimension and grain size is carefully tuned following a pareto-optimality analysis. The effect of grain and bond parameters is also examined in details with a sensitivity analysis. Finally, calibration to laboratory analogs of planetary porous ice is performed following a proposed probabilistic method. The cohesion energy density and the friction coefficient were found to be descriptive parameters that established a link between the micro- and macro-mechanical properties of porous ice. The model also revealed good correspondence between the evolution of the bond strength and the overall sample strength, which suggests that the strengthening of ice in the sample resulted from the evolution of a large-scale network due to intergranular bonding. Our results demonstrate that this methodology can provide a critical link between theoretical and experimental studies, and show the critical impact of sintering on the mechanical properties of ice plume deposits to design robust robotic systems.