Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published June 2023 | Supplemental Material
Journal Article Open

Inferring the Mean Thickness of the Outer Ice Shell of Enceladus From Diurnal Crustal Deformation


The thickness of the outer ice shell plays an important role in several geodynamical processes at ocean worlds. Here, we show that observations of tidally driven diurnal surface displacements can constrain the mean ice shell thickness, dᵢ꜀ₑ. Such estimates are sensitive to any significant structural features that break spherical symmetry such as faults and lateral variation in ice shell thickness and structure. We develop a finite-element model of Enceladus to calculate diurnal tidal displacements for a range of dᵢ꜀ₑ values in the presence of such structural heterogeneities. Consistent with results from prior studies, we find that the presence of variations in ice shell thickness can significantly amplify deformation in thinned regions. If major faults are also activated by tidal forcing—such as Tiger Stripes on Enceladus—their characteristic surface displacement patterns could easily be measured using modern geodetic methods. Within the family of Enceladus models explored, estimates of dᵢ꜀ₑ that assume spherical symmetry a priori can deviate from the true value by as much as ∼41% when structural heterogeneities are present. Additionally, we show that crustal heterogeneities near the South Pole produce differences of up to 35% between Love numbers evaluated at different spherical harmonic orders. A ∼41% range in estimates of dᵢ꜀ₑ from Love numbers is smaller than that found with approaches relying on static gravity and topography (∼250%) or analyzing diurnal libration amplitudes (∼85%) to infer dᵢ꜀ₑ at Enceladus. As such, we find that analysis of diurnal tidal deformation is a relatively robust approach to inferring mean crustal thickness.

Additional Information

© 2023 American Geophysical Union. We would like to express our gratitude to the reviewers and editors for their valuable contributions in improving the clarity and content of this manuscript. This research was supported by the Future Investigators in NASA Earth and Space Science and Technology (FINESST) Program (80NSSC22K1318). We also thank the Keck Institute for Space Studies (KISS) at California Institute of Technology for organizing two workshops about "Next-Generation Planetary Geodesy" which provided insight, expertise, and discussions that greatly assisted the research. We also thank Matthew Knepley, Brad Aagaard, and Charles Williams for providing invaluable advice to modify PyLith for the simulations described this work. A portion of this research was supported by a Strategic Research and Technology Development task led by James T. Keane and Ryan S. Park at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). Data Availability Statement: The data used in this study were generated using the software package PyLith (Aagaard et al., 2007, 2022). PyLith is an open-source finite element code for modeling geodynamic processes and is available on GitHub and Zenodo repositories (Aagaard et al., 2022). The specific PyLith version used in this study was v2.2.2. PyLith input files, post-processing scripts, and selected output files for this work are available on (Berne, 2023). The mesh geometries utilized in this study were created using CUBIT (v15.2), a node-locked licensed software which is available through the developer Sandia National Laboratories (CoreForm, 2020; Skroch et al., 2019).

Attached Files

Supplemental Material - 2022je007712-sup-0001-supporting_information_si-s01.pdf


Files (1.7 MB)

Additional details

August 22, 2023
October 20, 2023