Abstract
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.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
Purchase on Springer Link
Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Stern, S. et al. The Pluto system: initial results from its exploration by New Horizons. Science 350, http://dx.doi.org/10.1126/science.aad1815 (2015)
Harry, D. & Gozdzik, J. Ice wedges: growth, thaw transformation, and palaeoenvironmental significance. J. Quat. Sci. 3, 39–55 (1988)
Kindle, E. Some factors affecting the development of mud-cracks. J. Geol. 25, 135–144 (1917)
Lachenbruch, A. Mechanics of thermal contraction cracks and ice-wedge polygons in permafrost. Geol. Soc. Am. Spec. Pap. 70, 1–66 (1962)
Stachowiak, P., Sumarokov, V., Mucha, J. & Jeżowski, A. Thermal conductivity of solid nitrogen. Phys. Rev. B 50, 543–546 (1994)
Hansen, C. & Paige, D. Seasonal nitrogen cycles on Pluto. Icarus 120, 247–265 (1996)
McGill, G. & Hills, L. Origin of giant Martian polygons. J. Geophys. Res. 97, 2633–2647 (1992)
Pechmann, J. The origin of polygonal troughs on the Northern Plains of Mars. Icarus 42, 185–210 (1980)
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)
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)
Schubert, G., Turcotte, D. & Olson, P. Mantle Convection in the Earth and Planets (Cambridge Univ. Press, 2001)
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)
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)
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)
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)
Moresi, L. & Solomatov, V. Numerical investigation of 2D convection with extremely large viscosity variations. Phys. Fluids 7, 2154–2162 (1995)
Angwin, M. Nitrogen–carbon monoxide phase diagram. J. Chem. Phys. 44, 417–418 (1966)
Zhao, W., Yuen, D. & Honda, S. Multiple phase transitions and the style of mantle convection. Phys. Earth Planet. Inter. 72, 185–210 (1992)
Christensen, U. & Yuen, D. The interaction of a subducting lithospheric slab with a chemical or phase boundary. J. Geophys. Res. 89, 4389–4402 (1984)
Schubert, G., Yuen, D. & Turcotte, D. Role of phase transitions in a dynamic mantle. Geophys. J. Int. 42, 705–735 (1975)
Scott, T. Solid and liquid nitrogen. Phys. Rep. 27, 89–157 (1976)
Niemela, J., Skrbek, L., Sreenivasan, K. & Donnelly, R. Turbulent convection at very high Rayleigh numbers. Nature 404, 837–840 (2000)
Schubert, G. Numerical models of mantle convection. Annu. Rev. Fluid Mech. 24, 359–394 (1992)
Karato, S. Deformation of Earth Materials: an Introduction to the Rheology of Solid Earth 338–362 (Cambridge Univ. Press, 2012)
Eisenberg, D. S. & Kauzmann, W. The Structure and Properties of Water 296 (Clarendon Press, 1969)
Hobbs, P. Ice Physics 346 (Oxford Univ. Press, 2010)
Acknowledgements
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.
Author information
Authors and Affiliations
Contributions
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.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing financial interests.
Additional information
Reviewer Information Nature thanks G. Schubert and the other anonymous reviewer(s) for their contribution to the peer review of this work.
Rights and permissions
About this article
Cite this article
Trowbridge, A., Melosh, H., Steckloff, J. et al. Vigorous convection as the explanation for Pluto’s polygonal terrain. Nature 534, 79–81 (2016). https://doi.org/10.1038/nature18016
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/nature18016
This article is cited by
-
Sublimation-driven convection in Sputnik Planitia on Pluto
Nature (2021)
-
Recent Advancements and Motivations of Simulated Pluto Experiments
Space Science Reviews (2018)
-
Penitentes as the origin of the bladed terrain of Tartarus Dorsa on Pluto
Nature (2017)
-
Pluto's polygons explained
Nature (2016)
-
Reorientation and faulting of Pluto due to volatile loading within Sputnik Planitia
Nature (2016)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.