Seismic Wavefield Modeling of Enceladus: Challenges and Opportunities Presented by a 3D Ice Shell

Abstract

Understanding the interior structures of icy moons will be crucial in untangling narratives of formation and evolution, both within our solar system and beyond it. Seismology is a proven and unparalleled methodology for investigating the deep interiors of planetary bodies but has never been deployed on an icy moon. To improve future mission design, we conduct seismic simulations for Saturn's icy moon Enceladus which account for the unique seismic responses of icy ocean worlds. We discover that even with high surface temperatures at the south pole and 3D ice thickness models, seismic amplitudes are two orders of magnitude higher than the self-noise of mission-candidate instrumentation. We compare the effects of a 2D and 3D ice shell to determine the detail of seismic inversion for ice shell properties and how this varies with source and receiver location. We also compare the travel time differences caused by ice shell variation with potential effects from the uncertain core structure and discover that these two sources of travel time perturbation have similar magnitudes but could be distinguished through careful inversion strategy. We investigate varied source types to represent focal mechanisms likely to be present at the south pole of Enceladus. We finally make recommendations supporting landing sites between 20 and 30$°$ from the south pole that should enable observation of a wide range of seismic phases, including core-transmitted phases that could constrain core velocities.