Powering prolonged hydrothermal activity inside Enceladus

Abstract

Geophysical data from the Cassini spacecraft imply the presence of a global ocean underneath the ice shell of Enceladus1, only a few kilometres below the surface in the South Polar Terrain2,3,4. Chemical analyses indicate that the ocean is salty5 and is fed by ongoing hydrothermal activity6,7,8. In order to explain these observations, an abnormally high heat power (>20 billion watts) is required, as well as a mechanism to focus endogenic activity at the south pole9,10. Here, we show that more than 10 GW of heat can be generated by tidal friction inside the unconsolidated rocky core. Water transport in the tidally heated permeable core results in hot narrow upwellings with temperatures exceeding 363 K, characterized by powerful (1–5 GW) hotspots at the seafloor, particularly at the south pole. The release of heat in narrow regions favours intense interaction between water and rock, and the transport of hydrothermal products from the core to the plume sources. We are thus able to explain the main global characteristics of Enceladus: global ocean, strong dissipation, reduced ice-shell thickness at the south pole and seafloor activity. We predict that this endogenic activity can be sustained for tens of millions to billions of years.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Tidal friction in the porous core of Enceladus saturated with liquid water.
Fig. 2: Synthetic characteristics for porous convection of liquid water with heterogeneous tidal heating of the rocky core.
Fig. 3: Heat flux pattern at the interface between rocky core and ocean.
Fig. 4: Hotpots at the seafloor.

References

  1. 1.

    Thomas, P. C. et al. Enceladus’s measured physical libration requires a global subsurface ocean. Icarus 264, 37–47 (2016).

    ADS  Article  Google Scholar 

  2. 2.

    Čadek, O. et al. Enceladus’s internal ocean and ice shell constrained from Cassini gravity, shape, and libration data. Geophys. Res. Lett. 43, 5653–5660 (2016).

    ADS  Article  Google Scholar 

  3. 3.

    Beuthe, M., Rivoldini, A. & Trinh, A. Enceladus’s and Dione’s floating ice shells supported by minimum stress isostasy. Geophys. Res. Lett. 43, 10088–10096 (2016).

    ADS  Article  Google Scholar 

  4. 4.

    Le Gall, A. et al. Thermally anomalous features in the subsurface of Enceladus’s south polar terrain. Nat. Astron 1, 0063 (2017).

    Article  Google Scholar 

  5. 5.

    Postberg, F. et al. Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus. Nature 459, 1098–1101 (2009).

    ADS  Article  Google Scholar 

  6. 6.

    Hsu, H.-W. et al. Ongoing hydrothermal activities within Enceladus. Nature 519, 207–210 (2015).

    ADS  Article  Google Scholar 

  7. 7.

    Sekine, Y. et al. High-temperature water–rock interactions and hydrothermal environments in the chondrite-like core of Enceladus. Nat. Commun 6, 8604 (2015).

    Article  Google Scholar 

  8. 8.

    Waite, J. H. et al. Cassini finds molecular hydrogen in the Enceladus plume: evidence for hydrothermal processes. Science 356, 155–159 (2017).

    ADS  Article  Google Scholar 

  9. 9.

    Porco, C. C. et al. Cassini observes the active south pole of Enceladus. Science 311, 1393–1401 (2006).

    ADS  Article  Google Scholar 

  10. 10.

    Spencer, J. R. et al. Cassini encounters Enceladus: background and the discovery of a south polar hot spot. Science 311, 1401–1405 (2006).

    ADS  Article  Google Scholar 

  11. 11.

    Souček, O., Hron, J., Běhounková, M. & Čadek, O. Effect of the tiger stripes on the deformation of Saturn’s moon Enceladus. Geophys. Res. Lett. 43, 7417–7423 (2016).

    ADS  Article  Google Scholar 

  12. 12.

    Běhounková, M., Souček, O., Hron, J. & Čadek, O. Plume activity and tidal deformation on Enceladus influenced by faults and variable ice shell thickness. Astrobiology 17, 941–954 (2017).

    ADS  Google Scholar 

  13. 13.

    McKinnon, W. B. The shape of Enceladus as explained by an irregular core: implications for gravity, libration, and survival of its subsurface ocean. J. Geophys. Res. 118, 1775–1788 (2013).

    Article  Google Scholar 

  14. 14.

    Monteux, J., Collins, G. S., Tobie, G. & Choblet, G. Consequences of large impacts on Enceladus’ core shape. Icarus. 264, 300–310 (2016).

    ADS  Article  Google Scholar 

  15. 15.

    Neveu, M. & Rhoden, A. R. The origin and evolution of a differentiated Mimas. J. Geophys. Res. 296, 183–196 (2015).

    Google Scholar 

  16. 16.

    Travis, B. J. & Schubert, G. Keeping Enceladus warm. Icarus 250, 32–42 (2015).

    ADS  Article  Google Scholar 

  17. 17.

    Roberts, J. H. The fluffy core of Enceladus. Icarus 258, 54–66 (2015).

    ADS  Article  Google Scholar 

  18. 18.

    Rollins, K. M., Evans, M. D., Diehl, N. B. & Daily, W. D. Shear modulus and damping relationships for gravels. J. Geotech. Geoenviron. Eng 124, 396–405 (1998).

    Article  Google Scholar 

  19. 19.

    Hedman, M. M. et al. An observed correlation between plume activity and tidal stresses on Enceladus. Nature 500, 182–184 (2013).

    ADS  Article  Google Scholar 

  20. 20.

    Nimmo, F., Porco, C. C. & Mitchell, C. Tidally modulated eruptions on Enceladus: Cassini ISS observations and models. Astron. J. 148, 46 (2014).

    ADS  Article  Google Scholar 

  21. 21.

    Běhounkovà, M. et al. Timing of water plume eruptions on Enceladus explained by interior viscosity structure. Nat. Geosci 8, 601 (2015).

    ADS  Article  Google Scholar 

  22. 22.

    Monnereau, M. & Dubuffet, F. Is Io’s mantle really molten? Icarus 158, 450–459 (2002).

    ADS  Article  Google Scholar 

  23. 23.

    Soderlund, K. M., Schmidt, B. E., Wicht, J. & Blankenship, D. D. Ocean-driven heating of Europa’s icy shell at low latitudes. Nat. Geosci 7, 16–19 (2014).

    ADS  Article  Google Scholar 

  24. 24.

    Grannan, A. M., Favier, B., Le Bars, M. & Aurnou, J. M. Tidally forced turbulence in planetary interiors. Geophys. J. Int. 208, 1690–1703 (2016).

    ADS  Google Scholar 

  25. 25.

    Lainey, V. et al. New constraints on Saturn’s interior from Cassini astrometric data. Icarus 281, 286–296 (2017).

    ADS  Article  Google Scholar 

  26. 26.

    Fuller, J., Luan, J. & & Quataert, E. Resonance locking as the source of rapid tidal migration in the Jupiter and Saturn moon systems. Mon. Not. R. Astr. Soc. 458, 3867–3879 (2016).

    ADS  Article  Google Scholar 

  27. 27.

    Postberg, F. et al. The E ring in the vicinity of Enceladus. II. Probing the moon’s interior—the composition of E-ring particles. Icarus 193, 438–454 (2008).

    ADS  Article  Google Scholar 

  28. 28.

    Iess, L. et al. The gravity field and interior structure of Enceladus. Science 344, 78–80 (2014).

    ADS  Article  Google Scholar 

  29. 29.

    McKinnon, W. B. Effect of Enceladus’s rapid synchronous spin on interpretation of Cassini gravity. Geophys. Res. Lett. 42, 2137–2143 (2015).

    ADS  Article  Google Scholar 

  30. 30.

    Fountain, A. G. & Walder, J. S. Water flow through temperate glaciers. Rev. Geophys. 36, 299–328 (1998).

    ADS  Article  Google Scholar 

  31. 31.

    Johnson, J. W., Oelkers, E. H. & Helgeson, H. C. SUPCRT92: a software package for calculating the standard molal thermodynamic properties of minerals, gases, aqueous species, and reactions from 1 to 5000 bar and 0 to 1000 °C. Chem. Geol. 18, 899–947 (1992).

    Google Scholar 

  32. 32.

    Johnson, J. W. & Norton, D. Critical phenomena in hydrothermal systems; state, thermodynamic, electrostatic, and transport properties of H2O in the critical region. Am. J. Sci. 291, 541–648 (1991).

    ADS  Article  Google Scholar 

  33. 33.

    Ishibashi, I. & Zhang, X. Unified dynamic shear moduli and damping ratios of sand and clay. Soils Found. 33, 182–191 (1993).

    Article  Google Scholar 

  34. 34.

    Fiscina, J. E. et al. Dissipation in quasistatically sheared wet and dry sand under confinement. Phys. Rev. E 86, 020103 (2012).

    ADS  Article  Google Scholar 

  35. 35.

    Wulff, A. M., Hashida, T., Watanabe, K. & Takahashi, H. Attenuation behaviour of tuffaceous sandstone and granite during microfracturing. Geophys. J. Int. 139, 395–409 (1999).

    ADS  Article  Google Scholar 

  36. 36.

    Brennan, A. J., Thusyanthan, N. I. & Madabhushi, S. P. Evaluation of shear modulus and damping in dynamic centrifuge tests. J. Geotech. Geoenviron. Eng 131, 1488–1497 (2005).

    Article  Google Scholar 

  37. 37.

    Seed, H. B., Wong, R. T., Idriss, I. M. & Tokimatsu, K. Moduli and damping factors for dynamic analyses of cohesionless soils. J. Geotech. Geoenviron. Eng 112, 1016–1032 (1986).

    Article  Google Scholar 

  38. 38.

    Segatz, M., Spohn, T., Ross, M. N. & Schubert, G. Tidal dissipation, surface heat flow, and figure of viscoelastic models of Io. Icarus 75, 187–206 (1988).

    ADS  Article  Google Scholar 

  39. 39.

    Tobie, G., Mocquet, A. & Sotin, C. Tidal dissipation within large icy satellites: Appli- cations to Europa and Titan. Icarus 177, 534–549 (2005).

    ADS  Article  Google Scholar 

  40. 40.

    Shibuya, S., Mitachi, T., Fukuda, F. & Degoshi, T. Strain rate effects on shear modulus and damping of normally consolidated clay. Geotech. Test. J. 18, 365–375 (1995).

    Article  Google Scholar 

  41. 41.

    Sun, J. I., Golesorki, R. & Seed, H. B. Dynamic Moduli and Damping Ratios for Cohesive Soils. (Earthquake Engineering Research Center, Univ, California, Berkeley, 1988). Report no. UCB/EERC-88/15.

    Google Scholar 

  42. 42.

    Araei, A. A., Razeghi, H. R., Tabatabaei, S. H. & Ghalandarzadeh, A. Loading fre- quency effect on stiffness, damping and cyclic strength of modeled rockfill materials. Soil Dyn. Earthq. Eng. 33, 1–18 (2012).

    Article  Google Scholar 

  43. 43.

    Zhou, W., Chen, Y., Ma, G., Yang, L. & Chang, X. A modified dynamic shear modulus model for rockfill materials under a wide range of shear strain amplitudes. Soil Dyn. Earthq. Eng 92, 229–238 (2017).

    Article  Google Scholar 

  44. 44.

    Wichtmann, T., Niemunis, A. & Triantafyllidis, T. Strain accumulation in sand due to cyclic loading: drained triaxial tests. Soil Dyn. Earthq. Eng 25, 967–979 (2005).

    Article  Google Scholar 

  45. 45.

    Raad, L., Minassian, G. H. & Gartin, S. Characterization of saturated granular bases under repeated loads. Transp. Res. Rec. 369, 73–82 (1992).

  46. 46.

    Faul, U. H. & Jackson, I. The seismological signature of temperature and grain size variations in the upper mantle. Earth Planet. Sci. Lett. 234, 119–134 (2005).

    ADS  Article  Google Scholar 

  47. 47.

    Cole, D. M. A model for the anelastic straining of saline ice subjected to cyclic loading. Phil. Mag. A 72, 231–248 (1995).

    ADS  Article  Google Scholar 

  48. 48.

    Castillo-Rogez, J. C., Efroimsky, M. & Lainey, V. The tidal history of Iapetus: spin dynamics in the light of a refined dissipation model. J. Geophys. Res. 116, E09008 (2011).

    ADS  Article  Google Scholar 

  49. 49.

    Takeushi H., Saito M. in Methods in Computational Physics Vol. 1 (ed. Bolt, B. A.)217–295 (Academic, New York, 1972).

  50. 50.

    Saito, M. Some problems of static deformation of the Earth. J. Phys. Earth 22, 123–140 (1974).

    Article  Google Scholar 

  51. 51.

    Ricard, Y. in Mantle Dynamics. Treatise on Geophysics Vol. 7 (ed. Schubert, G.) 23–71 (Elsevier, Amsterdam, The Netherlands, 2015).

  52. 52.

    Kalousová, K., Souček, O., Tobie, G., Choblet, G. & Čadek, O. Ice melting and down- ward transport of meltwater by two-phase flow in Europa’s ice shell. J. Geophys. Res. 119, 532–549 (2014).

    Article  Google Scholar 

  53. 53.

    Palme, H. & O’Neill, H. S. C. in Mantle and Core. Treatise on Geochemistry Vol. 2 (ed. Carlson, R. W.) 1–38 (Elsevier, Amsterdam, The Netherlands, 2003).

  54. 54.

    Choblet, G. Modelling thermal convection with large viscosity gradients in one block of the cubed sphere. J. Comput. Phys. 205, 269–291 (2005).

    ADS  Article  MATH  Google Scholar 

  55. 55.

    Choblet, G., Čadek, O., Couturier, F. & Dumoulin, C. ŒDIPUS: a new tool to study the dynamics of planetary interiors. Geophys. J. Int 170, 9–30 (2007).

    ADS  Article  Google Scholar 

  56. 56.

    Goodman, J. C., Collins, G. C., Marshall, J. & Pierrehumbert, R. T. Hydrothermal plume dynamics on Europa: implications for chaos formation. J. Geophys. Res. 109, E03008 (2004).

    ADS  Article  Google Scholar 

  57. 57.

    Goodman, J. C. & Lenferink, E. Numerical simulations of marine hydrothermal plumes for Europa and other icy worlds. Icarus 221, 970–983 (2012).

    ADS  Article  Google Scholar 

Download references

Acknowledgements

The research leading to these results received financial support from the CNRS PICS (G.C., G.T.), the CNRS-INSU PNP program (G.C., G.T.) and the ANR OASIS project (G.C., G.T.), from the Czech Science Foundation project 15-14263Y (OS), from the German Research Foundation DFG projects PO 1015/2-1, /3-1, /4-1 (F.P.) and from the Icy Worlds node of NASA’s Astrobiology Institute 13-NAI7-0024 (C.S.). The computations were carried out using CCIPL computational facilities (France).

Author information

Affiliations

Authors

Contributions

All authors contributed to the discussions and commented on the manuscript. G.C. and G.T. led the writing of the letter. C.S. performed calculations on core porosity. G.T. computed the tidal dissipation in the porous core. G.C. developed the 3D code of porous water flow and conducted the numerical simulations of porous convection. All authors contributed to the interpretation of results.

Corresponding author

Correspondence to Gaël Choblet.

Ethics declarations

Competing Interests

The authors declare no competing financial interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Electronic supplementary material

Supplementary Information

Supplementary Sections 1–2, Supplementary References, Supplementary Tables 1–4, and Supplementary Figures 1–9

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Choblet, G., Tobie, G., Sotin, C. et al. Powering prolonged hydrothermal activity inside Enceladus. Nat Astron 1, 841–847 (2017). https://doi.org/10.1038/s41550-017-0289-8

Download citation

Further reading

Search

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing