Seismic wavefield modelling 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 - 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.