After discovering a jet activity near the south pole of Saturn's moon Enceladus, the Cassini mission demonstrated the existence of a subsurface water ocean with a unique sampling opportunity through flybys. Diurnal variations in the observed brightness of the plume suggest a tidal control, although the existence and timing of two activity maxima seem to contradict stress analysis predictions. Here, we re-interpret the observed plume variability by combining a 3D global model of tidal deformation of the fractured ice shell with a 1D local model of transport processes within south-polar faults. Our model successfully predicts the observed plume's temporal variability by combining two independent vapour transport mechanisms: slip-controlled jet flow and normal-stress-controlled ambient flow. Moreover, it provides a possible explanation for the differences between the vapour and solid emission rates during the diurnal cycle and the observed fractionation of the various icy particle families. Our model prediction could be tested by future JWST observations targeted when Enceladus is at different positions on its orbit and could be used to determine the optimal strategy for plume material sampling by future space missions.

Department of Geophysics Faculty of Mathematics and Physics Charles University Prague Czech Republic

Institute of Hydrogeology Engineering Geology and Applied Geophysics Faculty of Science Charles University Prague Czech Republic

Laboratoire de Planétologie et Géosciences UMR 6112 Nantes Université Univ Angers Le Mans Université CNRS Nantes France

Mathematical Institute Faculty of Mathematics and Physics Charles University Prague Czech Republic

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Hurford, T. A., Helfenstein, P., Hoppa, G. V., Greenberg, R. & Bills, B. G. Eruptions arising from tidally controlled periodic openings of rifts on Enceladus. Nature447, 292–294 (2007). 10.1038/nature05821 PubMed DOI

Hurford, T. A. et al. Geological implications of a physical libration on Enceladus. Icarus203, 541–552 (2009).10.1016/j.icarus.2009.04.025 DOI

Hedman, M. M. et al. An observed correlation between plume activity and tidal stresses on Enceladus. Nature500, 182–184 (2013). 10.1038/nature12371 PubMed DOI

Nimmo, F., Porco, C. & Mitchell, C. Tidally modulated eruptions on Enceladus: Cassini ISS observations and models. The Astronomical Journal148, 46 (2014).10.1088/0004-6256/148/3/46 DOI

Porco, C. C., DiNino, D. & Nimmo, F. How the Geysers, Tidal Stresses, and Thermal Emission Across the South Polar Terrain of Enceladus Are Related. The Astronomical Journal148, 45 (2014).10.1088/0004-6256/148/3/45 DOI

Saur, J. et al. Evidence for temporal variability of Enceladus’ gas jets: Modeling of Cassini observations. Geophysical Research Letters35, 10.1029/2008GL035811 (2008).

Hansen, C. J. et al. The composition and structure of Enceladus’ plume from the complete set of Cassini UVIS occultation observations. Icarus344, 113461 (2020).10.1016/j.icarus.2019.113461 DOI

Teolis, B. et al. Enceladus plume structure and time variability: comparison of Cassini observations. Astrobiology17, 926–940 (2017). 10.1089/ast.2017.1647 PubMed DOI PMC

Villanueva, G.L. et al. JWST molecular mapping and characterization of Enceladus’ water plume feeding its torus. Nature Astronomy, 10.1038/s41550-023-02009-6 (2023).

Denny, K. E., Hedman, M. M., Bockelée-Morvan, D., Filacchione, G. & Capaccioni, F. Constraining time variations in enceladus’s water-vapor plume with near-infrared spectra from cassini’s visual and infrared mapping spectrometer. The Planetary Science Journal5, 144 (2024).10.3847/PSJ/ad4c69 DOI

Běhounková, M. et al. Timing of water plume eruptions on Enceladus explained by interior viscosity structure. Nature Geosci.8, 601–604 (2015).10.1038/ngeo2475 DOI

Beuthe, M., Rivoldini, A. & Trinh, A. Enceladus’s and dione’s floating ice shells supported by minimum stress isostasy. Geophysical Research Letters43, 10088–10096 (2016).10.1002/2016GL070650 DOI

Čadek, O. et al. Enceladus’s internal ocean and ice shell constrained from cassini gravity, shape, and libration data. Geophysical Research Letters46, 5653–5660 (2016).10.1002/2016GL068634 DOI

Čadek, O. et al. Long-term stability of Enceladus’ uneven ice shell. Icarus319, 476–484 (2019).10.1016/j.icarus.2018.10.003 DOI

Hemingway, D. J. & Mittal, T. Enceladus’s ice shell structure as a window on internal heat production. Icarus332, 111–131 (2019).10.1016/j.icarus.2019.03.011 DOI

Běhounková, M., Souček, O., Hron, J. & Čadek, O. Plume activity and tidal deformation on Enceladus influenced by faults and variable ice shell thickness. Astrobiology17, 941–954 (2017). 10.1089/ast.2016.1629 PubMed DOI PMC

Souček, O. et al. Tidal dissipation in Enceladus’ uneven, fractured ice shell. Icarus328, 218–231 (2019).10.1016/j.icarus.2019.02.012 DOI

Thomas, P. C. et al. Enceladus’s measured physical libration requires a global subsurface ocean. Icarus264, 37–47 (2016).10.1016/j.icarus.2015.08.037 DOI

Pleiner Sládková, K., Souček, O. & Běhounková, M. Enceladus’ tiger stripes as frictional faults: Effect on stress and heat production. Geophysical Research Letters48, 2021–094849 (2021).10.1029/2021GL094849 DOI

Berne, A. et al. Jet activity on Enceladus linked to tidally driven strike-slip motion along tiger stripes. Nature Geoscience17, 385–391 (2024).10.1038/s41561-024-01418-0 DOI

Schmidt, J., Brilliantov, N., Spahn, F., Kempf, S. Slow dust in Enceladus’ plume from condensation and wall collisions in tiger stripe fractures. Nature451, 10.1038/nature06491 (2008). PubMed

Ingersoll, A. P. & Pankine, A. A. Subsurface heat transfer on Enceladus: Conditions under which melting occurs. Icarus206, 594–607 (2010).10.1016/j.icarus.2009.09.015 DOI

Kite, E. S. & Rubin, A. M. Sustained eruptions on Enceladus explained by turbulent dissipation in tiger stripes. Proceedings of the National Academy of Sciences113, 201520507 (2016).10.1073/pnas.1520507113 PubMed DOI PMC

Nakajima, M. & Ingersoll, A. P. Controlled boiling on Enceladus. 1. model of the vapor-driven jets. Icarus272, 309–318 (2016).10.1016/j.icarus.2016.02.027 DOI

Spencer, J.R. et al. Plume Origins and Plumbing: From Ocean to Surface. In: Schenk, P.M., Clark, R.N., Howett, C.J.A., Verbiscer, A.J., Waite, J.H. (eds.) Enceladus and the Icy Moons of Saturn, p. 163, 10.2458/azu_uapress_9780816537075-ch008 (2018).

Elsworth, D. & Goodman, R. E. Characterization of rock fissure hydraulic conductivity using idealized wall roughness profiles. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts23, 233–243 (1986).10.1016/0148-9062(86)90969-1 DOI

Ingersoll, A. P., Ewald, S. P. & Trumbo, S. K. Time variability of the Enceladus plumes: orbital periods, decadal periods, and aperiodic change. Icarus344, 113345 (2020).10.1016/j.icarus.2019.06.006 DOI

Oksanen, P. & Keinonen, J. The mechanism of friction of ice. Wear78, 315–324 (1982).10.1016/0043-1648(82)90242-3 DOI

Yin, A., Zuza, A. V. & Pappalardo, R. T. Mechanics of evenly spaced strike-slip faults and its implications for the formation of tiger-stripe fractures on Saturn’s moon Enceladus. Icarus266, 204–216 (2016).10.1016/j.icarus.2015.10.027 DOI

Rossi, C., Cianfarra, P., Salvini, F., Bourgeois, O. & Tobie, G. Tectonics of Enceladus’ south pole: Block rotation of the tiger stripes. Journal of Geophysical Research: Planets125, 2020–006471 (2020).

Petrovic, J. Review mechanical properties of ice and snow. Journal of materials science38, 1–6 (2003).10.1023/A:1021134128038 DOI

Postberg, F. et al. Plume and Surface Composition of Enceladus, pp. 129–162. University of Arizona Press, Tucson, http://www.jstor.org/stable/j.ctv65sw2b.16 (2018). Accessed 2023-06-23.

Postberg, F. et al. The E-ring in the vicinity of Enceladus: II. probing the moon’s interior - the composition of E-ring particles. Icarus193, 438–454 (2008).10.1016/j.icarus.2007.09.001 DOI

Postberg, F. et al. Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus. Nature459, 1–4 (2009).10.1038/nature08046 PubMed DOI

Postberg, F., Schmidt, J., Hillier, J., Kempf, S. & Srama, R. A salt-water reservoir as the source of a compositionally stratified plume on Enceladus. Nature474, 620–622 (2011). 10.1038/nature10175 PubMed DOI

Postberg, F. et al. Detection of phosphates originating from Enceladus’s ocean. Nature618, 489–493 (2023). 10.1038/s41586-023-05987-9 PubMed DOI PMC

Marusiak, A. G. et al. Exploration of icy ocean worlds using geophysical approaches. The Planetary Science Journal2, 150 (2021).10.3847/PSJ/ac1272 DOI

Ermakov, A. I. et al. A recipe for the geophysical exploration of Enceladus. The Planetary Science Journal2, 157 (2021).10.3847/PSJ/ac06d2 DOI

Vance, S. et al. Distributed geophysical exploration of Enceladus and other ocean worlds. Bulletin of the AAS53, https://baas.aas.org/pub/2021n4i127 (2021).

Choblet, G. et al. Enceladus as a potential oasis for life: Science goals and investigations for future explorations. Experimental Astronomy54, 809–847 (2022).10.1007/s10686-021-09808-7 DOI

Souček, O. et al. Radar attenuation in Enceladus’ ice shell: Obstacles and opportunities for constraining shell thickness, chemistry, and thermal structure. Journal of Geophysical Research: Planets128, 2022–007626 (2023).

MacKenzie, S. M. et al. The Enceladus orbilander mission concept: Balancing return and resources in the search for life. The Planetary Science Journal2, 77 (2021).10.3847/PSJ/abe4da DOI

Savitzky, A. & Golay, M. J. E. Smoothing and differentiation of data by simplified least squares procedures. Analytical Chemistry36, 1627–1639 (1964).10.1021/ac60214a047 DOI

Virtanen, P. et al. SciPy 1.0: Fundamental Algorithms for Scientific Computing in Python. Nature Methods17, 261–272 (2020). 10.1038/s41592-019-0686-2 PubMed DOI PMC

Souček, O., Hron, J., Běhounková, M. & Čadek, O. Effect of the tiger stripes on the deformation of Saturn’s moon Enceladus. Geophysical Research Letters43, 7417–7423 (2016).10.1002/2016GL069415 DOI

Dong, Y., Hill, T.W., Teolis, B.D., Magee, B.A., Waite, J.H. The water vapor plumes of Enceladus. Journal of Geophysical Research: Space Physics 116, 10.1029/2011JA016693 (2011).

Hansen, C.J. et al. The composition and structure of the Enceladus plume. Geophysical Research Letters 38, 10.1029/2011GL047415 (2011).

Olsson, R. & Barton, N. An improved model for hydromechanical coupling during shearing of rock joints. International Journal of Rock Mechanics and Mining Sciences38, 317–329 (2001).10.1016/S1365-1609(00)00079-4 DOI

Schulson, E.M., Duval, P.Creep and Fracture of Ice. Cambridge University Press, Cambridge (2009).

Maugis, D.Contact, Adhesion and Rupture of Elastic Solids, 1st edn. Springer Series in Solid-State Sciences Nr. 130. Springer, Heidelberg (2000).

Marriott, M.Nalluri And Featherstone’s Civil Engineering Hydraulics: Essential Theory with Worked Examples, 6th edn. Wiley-Blackwell, Chichester (2016).

Foreman-Mackey, D., Hogg, D. W., Lang, D. & Goodman, J. emcee: The MCMC Hammer. Publications of the Astronomical Society of the Pacific125, 306 (2013).10.1086/670067 DOI

Goodman, J. & Weare, J. Ensemble samplers with affine invariance. Communications in Applied Mathematics and Computational Science5, 65–80 (2010).10.2140/camcos.2010.5.65 DOI

Souček, O., Běhounková, M., Lanzendörfer, M., Tobie, G., Choblet, G. Figshare repository for NCOMMS-23-38372B: “Variations in plume activity reveal the dynamics of water-filled faults on Enceladus”. Figshare, 10.6084/m9.figshare.26356342. (2024). PubMed

Tidal Deformation and Dissipation Processes in Icy Worlds

Variations in plume activity reveal the dynamics of water-filled faults on Enceladus