Jet activity on Enceladus linked to tidally driven strike-slip motion along tiger stripes
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1.
California Institute of Technology
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2.
Jet Propulsion Lab
Abstract
At Saturn’s moon Enceladus, jets along four distinct fractures called ‘tiger stripes’ erupt ice crystals into a broad plume above the South Pole. The tiger stripes experience variations in tidally driven shear and normal traction as Enceladus orbits Saturn. Here, we use numerical finite-element modelling of a spherical ice shell subjected to tidal forces to show that this traction may produce quasi-periodic strike-slip motion in the Enceladus crust with two peaks in activity during each orbit. We suggest that friction modulates the response of tiger stripes to driving stresses, such that tidal traction on the faults results in a difference in the magnitudes of peak strike slip and delays the first peak in fault motion following peak tidal stress. The simulated double-peaked and asymmetric strike-slip motion of the tiger stripes is consistent with diurnal variations in jet activity inferred from Cassini spacecraft images of plume brightness. The spatial distribution of strike-slip motion also matches Cassini infrared observations of heat flow. We hypothesize that strike-slip motion can extend transtensional bends (for example, pull-apart structures) along geometric irregularities over the tiger stripes and thus modulate jet activity. Tidally driven fault motion may also influence longer term tectonic evolution near the South Pole of the satellite.
Copyright and License
© 2024 Springer Nature Limited.
Acknowledgement
This research was supported by the Future Investigators in NASA Earth and Space Science and Technology (FINESST) Program (80NSSC22K1318)(A.B., M.S.). We thank the Keck Institute for Space Studies (KISS) at the California Institute of Technology for organizing two workshops about ‘Next-Generation Planetary Geodesy’ which provided insight, expertise and discussions that inspired this research. We also thank M. Knepley, B. Aagaard and C. Williams for providing valuable advice on how to modify PyLith for our simulations. A portion of this research was supported by a Strategic Research and Technology Development task led by J. T. Keane and R. S. Park at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004)(J.T.K., R.S.P.).
Data Availability
Data used for Fig. 3 (slab densities derived from Cassini ISS images) is publicly available via Time variability of the Enceladus plumes: Orbital periods, decadal periods, and aperiodic changehttps://doi.org/10.1016/j.icarus.2019.06.006 (ref. 7). Data used for Fig. 4 (heat flow along the tiger stripe faults derived from Cassini Composite Infrared Spectrometer measurements) is publicly available via Plume Origins and Plumbing (Ocean to Surface)https://doi.org/10.2458/azu_uapress_9780816537075-ch008 (ref. 4).
Code Availability
The results used in this study were generated using the software package PyLith44,50. PyLith is an open-source finite-element code for modelling geodynamic processes and is available via Zenodo at https://doi.org/10.5281/zenodo.3269486 (ref. 50). The specific PyLith version used in this study was v2.2.2. The full code used to simulate deformation in this work (including modifications Pylith, CUBIT and PETSc and a user manual) are publicly available via https://doi.org/10.5281/zenodo.10585162 (ref. 51). 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 via https://cubit.sandia.gov/2021/09/14/cubit-15-7-released-october-20-2020/ (ref. 48).
Supplemental Material
Supplementary Table 1.
Movies of tidally driven deformation at Enceladus over the full tidal cycle. Top: South Polar orthographic projections of radial displacement at the surface relative to that produced by models without tiger stripe faults. Bottom: perspective view of lateral slip along tiger stripe faults: ‘A’ Alexandria, ‘C’ Cairo, ‘B’ Baghdad and ‘D’ Damascus. We assign μ = 0.4 to tiger stripe faults for this example. Faults are viewed from 130° W, looking upward from 35° below the horizontal. Mean anomaly value (and relative distance of Enceladus to Saturn) is labelled above (and to the upper left) for reference.
Contributions
A.B. conceived and designed this study under the supervision of M.S. A.B. drafted the article and constructed Figs. 1–4. M.S., J.T.K. and A.B. developed numerical models used in the study. R.S.P. provided the shape model necessary for numerical simulations. J.T.K., with the aid of A.B., constructed Fig. 5. E.J.L. provided expertise regarding the geological evolution of the SPT. All authors discussed the results of the study and commented on the manuscript at each stage of revision.
Conflict of Interest
The authors declare no competing interests.
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Additional details
- National Aeronautics and Space Administration
- NASA Earth and Space Science and Technology Fellowship 80NSSC22K1318
- National Aeronautics and Space Administration
- 80NM0018D0004
- Accepted
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2024-03-08
- Available
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2024-04-29Published
- Caltech groups
- Division of Geological and Planetary Sciences (GPS), Keck Institute for Space Studies
- Publication Status
- Published