Numerical Investigation on the Feasibility of Estimating the Thickness of Europa's Ice Shell by a Planned Impact

The existence of a liquid water ocean under the icy surface of Jupiter's moon Europa has been considered highly probable for decades. It has been speculated that such an environment could host extraterrestrial life. However, the thickness of Europa's top layer of ice and the depth of the ocean underneath are currently unknown. The authors investigate the feasibility of using seismic-inversion analysis to estimate the thickness of the ice shell and the depth of the subsurface ocean in a hypothetical event, in which a spacecraft-released impactor makes a planned collision with Europa's surface. The wave motions on Europa's surface that would result from a planned impact could be measured by impactor-probes penetrated into the ice shell. This work uses finite element method (FEM) modeling of seismic wave propagation to compute wave motions with a guessed ice thickness and ocean depth as input. Inverse modeling is used to determine the input that produces the best results when comparing the computed wave motions attributable to the input to the wave motion owing to pseudotarget values for ice thickness and ocean depth. To arrive at the solution of the inverse problem, the genetic algorithm (GA) was employed. The presented numerical simulation demonstrates the potential of using the inverse-modeling method for estimating the thickness of Europa's ice shell.