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Vigorous convection as the explanation for Pluto’s polygonal terrain


Pluto’s surface is surprisingly young and geologically active1. One of its youngest terrains is the near-equatorial region informally named Sputnik Planum, which is a topographic basin filled by nitrogen (N2) ice mixed with minor amounts of CH4 and CO ices1. Nearly the entire surface of the region is divided into irregular polygons about 20–30 kilometres in diameter, whose centres rise tens of metres above their sides. The edges of this region exhibit bulk flow features without polygons1. Both thermal contraction and convection have been proposed to explain this terrain1, but polygons formed from thermal contraction (analogous to ice-wedges or mud-crack networks)2,3 of N2 are inconsistent with the observations on Pluto of non-brittle deformation within the N2-ice sheet. Here we report a parameterized convection model to compute the Rayleigh number of the N2 ice and show that it is vigorously convecting, making Rayleigh–Bénard convection the most likely explanation for these polygons. The diameter of Sputnik Planum’s polygons and the dimensions of the ‘floating mountains’ (the hills of of water ice along the edges of the polygons) suggest that its N2 ice is about ten kilometres thick. The estimated convection velocity of 1.5 centimetres a year indicates a surface age of only around a million years.

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Figure 1: New Horizon’s image of Sputnik Planum on Pluto.
Figure 2: Calculated convection for Sputnik Planum polygons.
Figure 3: The N2–CO phase diagram.

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  1. Stern, S. et al. The Pluto system: initial results from its exploration by New Horizons. Science 350, (2015)

  2. Harry, D. & Gozdzik, J. Ice wedges: growth, thaw transformation, and palaeoenvironmental significance. J. Quat. Sci. 3, 39–55 (1988)

    Article  Google Scholar 

  3. Kindle, E. Some factors affecting the development of mud-cracks. J. Geol. 25, 135–144 (1917)

    Article  ADS  Google Scholar 

  4. Lachenbruch, A. Mechanics of thermal contraction cracks and ice-wedge polygons in permafrost. Geol. Soc. Am. Spec. Pap. 70, 1–66 (1962)

    Google Scholar 

  5. Stachowiak, P., Sumarokov, V., Mucha, J. & Jeżowski, A. Thermal conductivity of solid nitrogen. Phys. Rev. B 50, 543–546 (1994)

    Article  ADS  CAS  Google Scholar 

  6. Hansen, C. & Paige, D. Seasonal nitrogen cycles on Pluto. Icarus 120, 247–265 (1996)

    Article  ADS  CAS  Google Scholar 

  7. McGill, G. & Hills, L. Origin of giant Martian polygons. J. Geophys. Res. 97, 2633–2647 (1992)

    Article  ADS  Google Scholar 

  8. Pechmann, J. The origin of polygonal troughs on the Northern Plains of Mars. Icarus 42, 185–210 (1980)

    Article  ADS  Google Scholar 

  9. Freed, A. et al. On the origin of graben and ridges within and near volcanically buried craters and basins in Mercury's northern plains. J. Geophys. Res. 117, E00L06 (2012)

    Google Scholar 

  10. Blair, D. et al. The origin of graben and ridges in Rachmaninoff, Raditladi, and Mozart basins, Mercury. J. Geophys. Res. Planets 118, 47–58 (2013)

    Article  ADS  Google Scholar 

  11. Schubert, G., Turcotte, D. & Olson, P. Mantle Convection in the Earth and Planets (Cambridge Univ. Press, 2001)

  12. Stern, S., Porter, S. & Zangari, A. On the roles of escape erosion and the viscous relaxation of craters on Pluto. Icarus 250, 287–293 (2015)

    Article  ADS  CAS  Google Scholar 

  13. Barr, A. & Hammond, N. A common origin for ridge-and-trough terrain on icy satellites by sluggish lid convection. Phys. Earth Planet. Inter. 249, 18–27 (2015)

    Article  ADS  Google Scholar 

  14. Kameyama, M. & Ogawa, M. Transitions in thermal convection with strongly temperature-dependent viscosity in a wide box. Earth Planet. Sci. Lett. 180, 355–367 (2000)

    Article  ADS  CAS  Google Scholar 

  15. Yamashita, Y., Kato, M. & Arakawa, M. Experimental study on the rheological properties of polycrystalline solid nitrogen and methane: implications for tectonic processes on Triton. Icarus 207, 972–977 (2010)

    Article  ADS  CAS  Google Scholar 

  16. Moresi, L. & Solomatov, V. Numerical investigation of 2D convection with extremely large viscosity variations. Phys. Fluids 7, 2154–2162 (1995)

    Article  ADS  Google Scholar 

  17. Angwin, M. Nitrogen–carbon monoxide phase diagram. J. Chem. Phys. 44, 417–418 (1966)

    Article  ADS  CAS  Google Scholar 

  18. Zhao, W., Yuen, D. & Honda, S. Multiple phase transitions and the style of mantle convection. Phys. Earth Planet. Inter. 72, 185–210 (1992)

    Article  ADS  CAS  Google Scholar 

  19. Christensen, U. & Yuen, D. The interaction of a subducting lithospheric slab with a chemical or phase boundary. J. Geophys. Res. 89, 4389–4402 (1984)

    Article  ADS  CAS  Google Scholar 

  20. Schubert, G., Yuen, D. & Turcotte, D. Role of phase transitions in a dynamic mantle. Geophys. J. Int. 42, 705–735 (1975)

    Article  Google Scholar 

  21. Scott, T. Solid and liquid nitrogen. Phys. Rep. 27, 89–157 (1976)

    Article  ADS  Google Scholar 

  22. Niemela, J., Skrbek, L., Sreenivasan, K. & Donnelly, R. Turbulent convection at very high Rayleigh numbers. Nature 404, 837–840 (2000)

    Article  ADS  CAS  Google Scholar 

  23. Schubert, G. Numerical models of mantle convection. Annu. Rev. Fluid Mech. 24, 359–394 (1992)

    Article  ADS  Google Scholar 

  24. Karato, S. Deformation of Earth Materials: an Introduction to the Rheology of Solid Earth 338–362 (Cambridge Univ. Press, 2012)

  25. Eisenberg, D. S. & Kauzmann, W. The Structure and Properties of Water 296 (Clarendon Press, 1969)

  26. Hobbs, P. Ice Physics 346 (Oxford Univ. Press, 2010)

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We thank all of the New Horizons team members, without whom none of this work would have been possible. We also thank T. Bowling, D. Minton, B. Hogan, J. Kendall, B. Link and C. Milbury for discussions. A.J.T. thanks the Fredrick N. Andrews Fellowship for funding.

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Authors and Affiliations



A.J.T. and H.J.M. conceived this work, developed the parameterized convection model, and conducted Rayleigh number calculations for this paper. J.K.S. developed Maxwell time arguments for ruling out thermal contraction, computed the surface and subsurface temperatures of Pluto, and calculated atmospheric pressures. A.M.F. advised A.J.T., and helped to edit and revise the manuscript.

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Correspondence to A. J. Trowbridge.

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The authors declare no competing financial interests.

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Reviewer Information Nature thanks G. Schubert and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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Trowbridge, A., Melosh, H., Steckloff, J. et al. Vigorous convection as the explanation for Pluto’s polygonal terrain. Nature 534, 79–81 (2016).

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