Ocean-driven heating of Europa’s icy shell at low latitudes

Abstract

The ice shell of Jupiter’s moon Europa is marked by regions of disrupted ice known as chaos terrains that cover up to 40% of the satellite’s surface, most commonly occurring within 40° of the equator1. Concurrence with salt deposits2 implies a coupling between the geologically active ice shell and the underlying liquid water ocean at lower latitudes. Europa’s ocean dynamics have been assumed to adopt a two-dimensional pattern3,4,5,6,7,8, which channels the moon’s internal heat to higher latitudes. Here we present a numerical model of thermal convection in a thin, rotating spherical shell where small-scale convection instead adopts a three-dimensional structure and is more vigorous at lower latitudes. Global-scale currents are organized into three zonal jets and two equatorial Hadley-like circulation cells. We find that these convective motions transmit Europa’s internal heat towards the surface most effectively in equatorial regions, where they can directly influence the thermo-compositional state and structure of the ice shell. We suggest that such heterogeneous heating promotes the formation of chaos features through increased melting of the ice shell and subsequent deposition of marine ice at low latitudes. We conclude that Europa’s ocean dynamics can modulate the exchange of heat and materials between the surface and interior and explain the observed distribution of chaos terrains.

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Figure 1: Convective flow structures, zonal flows and temperature fields in planetary convection models.
Figure 2: Radial velocity, meridional circulations and zonal flows in our Europa-like ocean model.
Figure 3: Simulated ocean temperature distributions.
Figure 4: Pattern of radial heat transfer.

References

  1. 1

    Figueredo, P. H. & Greeley, R. Resurfacing history of Europa from pole-to-pole geological mapping. Icarus 167, 287–312 (2004).

    Article  Google Scholar 

  2. 2

    Brown, M. E. & Hand, K. P. Salts and radiation products on the surface of Europa. Astron. J. 145, 110–110 (2013).

    Article  Google Scholar 

  3. 3

    Thomson, R. E. & Delaney, J. R. Evidence for a weakly stratified Europan ocean sustained by seafloor heat flux. J. Geophys. Res. 106, 12355–12365 (2001).

    Article  Google Scholar 

  4. 4

    Melosh, H. J., Ekholm, A. G., Showman, A. P. & Lorenz, R. D. The temperature of Europa’s subsurface water ocean. Icarus 168, 498–502 (2004).

    Article  Google Scholar 

  5. 5

    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).

    Article  Google Scholar 

  6. 6

    Vance, S. & Brown, J. M. Layering and double-diffusion style convection in Europa’s ocean. Icarus 177, 506–514 (2005).

    Article  Google Scholar 

  7. 7

    Vance, S. & Goodman, J. C. in Europa (eds Pappalardo, R. T., McKinnon, W. M. & Khurana, K. K.) 459–482 (Univ. Arizona Press, 2009).

    Google Scholar 

  8. 8

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

    Article  Google Scholar 

  9. 9

    Kivelson, M. G. et al. Galileo magnetometer measurements: A stronger case for a subsurface ocean at Europa. Science 289, 1340–1343 (2000).

    Article  Google Scholar 

  10. 10

    Collins, G. & Nimmo, F. in Europa (eds Pappalardo, R. T., McKinnon, W. M. & Khurana, K. K.) 259–281 (Univ. Arizona Press, 2009).

    Google Scholar 

  11. 11

    Greenberg, R., Hoppa, G. V., Tufts, B. R., Geissler, P. & Riley, J. Chaos on Europa. Icarus 141, 263–286 (1999).

    Article  Google Scholar 

  12. 12

    McKinnon, W. B. Convective instability in Europa’s floating ice shell. Geophys. Res. Lett. 26, 951–954 (1999).

    Article  Google Scholar 

  13. 13

    Pappalardo, R. T. & Barr, A. C. The origin of domes on Europa: The role of thermally induced compositional diapirism. Geophys. Res. Lett. 31, L01701 (2004).

    Google Scholar 

  14. 14

    Schmidt, B. E., Blankenship, D. D., Patterson, G. W. & Schenk, P. M. Active formation of chaos terrain over shallow subsurface water on Europa. Nature 479, 502–505 (2011).

    Article  Google Scholar 

  15. 15

    Hussmann, H., Spohn, T. & Wieczerkowski, K. Thermal equilibrium states of Europa’s ice shell: Implications for internal ocean thickness and surface heat flow. Icarus 156, 143–151 (2002).

    Article  Google Scholar 

  16. 16

    Beuthe, M. Spatial patterns of tidal heating. Icarus 223, 308–329 (2013).

    Article  Google Scholar 

  17. 17

    Heimpel, M. H. & Aurnou, J. M. Turbulent convection in rapidly rotating spherical shells: A model for equatorial and high latitude jets on Jupiter and Saturn. Icarus 187, 540–557 (2007).

    Article  Google Scholar 

  18. 18

    Aurnou, J. M., Heimpel, M. H., Allen, L., King, E. M. & Wicht, J. Convective heat transfer and the pattern of thermal emission on the gas giants. Geophys. J. Int. 173, 793–801 (2008).

    Article  Google Scholar 

  19. 19

    Julien, K., Knobloch, E., Rubio, A. M. & Vasil, G. M. Heat transport in low-Rossby-number Rayleigh–Bénard convection. Phys. Rev. Lett. 109, 254503 (2012).

    Article  Google Scholar 

  20. 20

    King, E. M., Stellmach, S. & Aurnou, J. M. Heat transfer by rapidly rotating Rayleigh–Bénard convection. J. Fluid Mech. 691, 568–582 (2012).

    Article  Google Scholar 

  21. 21

    Aurnou, J. M., Heimpel, M. H. & Wicht, J. The effects of vigorous mixing in a convective model of zonal flow on the Ice Giants. Icarus 190, 110–126 (2007).

    Article  Google Scholar 

  22. 22

    Soderlund, K. M., Heimpel, M. H., King, E. M. & Aurnou, J. M. Turbulent models of ice giant internal dynamics: Dynamos, heat transfer, and zonal flows. Icarus 224, 97–113 (2013).

    Article  Google Scholar 

  23. 23

    Lewis, E. L. & Perkin, R. G. Ice pumps and their rates. J. Geophys. Res. 91, 11756–11762 (1986).

    Article  Google Scholar 

  24. 24

    Moore, J. C., Reid, A. P. & Kipfstuhl, J. Microphysical and electrical properties of marine ice and its relationship to meteoric and sea ice. J. Geophys. Res. 99, 5171–5180 (1994).

    Article  Google Scholar 

  25. 25

    Oerter, H. et al. Evidence for basal marine ice in the Filchner–Ronne ice shelf. Nature 358, 399–401 (1992).

    Article  Google Scholar 

  26. 26

    Ojakangas, G. W. & Stevenson, D. J. Polar wander of an ice shell on Europa. Icarus 81, 242–270 (1989).

    Article  Google Scholar 

  27. 27

    Tyler, R. H. Magnetic remote sensing of Europa’s ocean tides. Icarus 211, 906–908 (2011).

    Article  Google Scholar 

  28. 28

    Christensen, U. R. & Wicht, J. in Treatise on Geophysics, Core Dynamics Vol. 8 (ed. Schubert, G.) 245–282 (Elsevier, 2007).

    Google Scholar 

  29. 29

    Vance, S. & Brown, J. M. Thermodynamic properties of aqueous MgSO4 to 800 MPa at temperatures from −20 to 100 °C and concentrations to 2.5 mol kg−1 from sound speeds, with applications to icy world oceans. Geochim. Cosmochim. Acta 110, 176–189 (2013).

    Article  Google Scholar 

  30. 30

    Kuang, W. & Bloxham, J. An earth-like numerical dynamo model. Nature 389, 371–374 (1997).

    Article  Google Scholar 

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Acknowledgements

This work was supported by the Institute for Geophysics of the Jackson School of Geosciences at The University of Texas at Austin (UTIG). Computational resources were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center. We thank M. Heimpel for providing the jovian-like model data in Fig. 1, T. Doggett for providing the geologic map of Europa in Supplementary Fig. 1, and J. Aurnou for providing Supplementary Fig. 2. This is UTIG contribution 2637.

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K.M.S. and B.E.S. conceived of this project and wrote the paper. K.M.S. did all calculations and carried out the simulation. J.W. provided the numerical model and contributed to the convective regime transition arguments. D.D.B. contributed to the terrestrial analogue arguments. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to K. M. Soderlund.

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The authors declare no competing financial interests.

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Soderlund, K., Schmidt, B., Wicht, J. et al. Ocean-driven heating of Europa’s icy shell at low latitudes. Nature Geosci 7, 16–19 (2014). https://doi.org/10.1038/ngeo2021

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