• A Corrigendum to this article was published on 06 July 2016

Abstract

The vast, deep, volatile-ice-filled basin informally named Sputnik Planum is central to Pluto’s vigorous geological activity1,2. Composed of molecular nitrogen, methane, and carbon monoxide ices3, but dominated by nitrogen ice, this layer is organized into cells or polygons, typically about 10 to 40 kilometres across, that resemble the surface manifestation of solid-state convection1,2. Here we report, on the basis of available rheological measurements4, that solid layers of nitrogen ice with a thickness in excess of about one kilometre should undergo convection for estimated present-day heat-flow conditions on Pluto. More importantly, we show numerically that convective overturn in a several-kilometre-thick layer of solid nitrogen can explain the great lateral width of the cells. The temperature dependence of nitrogen-ice viscosity implies that the ice layer convects in the so-called sluggish lid regime5, a unique convective mode not previously definitively observed in the Solar System. Average surface horizontal velocities of a few centimetres a year imply surface transport or renewal times of about 500,000 years, well under the ten-million-year upper-limit crater retention age for Sputnik Planum2. Similar convective surface renewal may also occur on other dwarf planets in the Kuiper belt, which may help to explain the high albedos shown by some of these bodies.

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Acknowledgements

New Horizons was built and operated by the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, USA, for NASA. We thank the many engineers who have contributed to the success of the New Horizons mission, and NASA’s Deep Space Network (DSN) for a decade of support of New Horizons. This work was supported by NASA’s New Horizons project.

Author information

Affiliations

  1. Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St Louis, Saint Louis, Missouri 63130, USA

    • William B. McKinnon
    •  & Teresa Wong
  2. Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, California 95064, USA

    • Francis Nimmo
  3. Lunar and Planetary Institute, Houston, Texas 77058, USA

    • Paul M. Schenk
  4. National Aeronautics and Space Administration (NASA) Ames Research Center, Moffett Field, California 94035, USA

    • Oliver L. White
    • , J. M. Moore
    • , O. M. Umurhan
    •  & K. E. Smith
  5. Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20723, USA

    • J. H. Roberts
    •  & H. A. Weaver
  6. Southwest Research Institute, Boulder, Colorado 80302, USA

    • J. R. Spencer
    • , S. A. Stern
    • , C. B. Olkin
    •  & L. A. Young
  7. Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22904, USA

    • A. D. Howard
  8. National Aeronautics and Space Administration (NASA) Ames Research Center, Moffett Field, California 94035, USA.

    • J. M. Moore
    • , R. Beyer
    • , D. Cruikshank
    • , C. Dalle Ore
    • , O. L. White
    • , O. M. Umurhan
    • , C. Chavez
    •  & K. E. Smith
  9. Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St Louis, Saint Louis, Missouri 63130, USA.

    • W. B. McKinnon
  10. Southwest Research Institute, Boulder, Colorado 80302, USA.

    • J. R. Spencer
    • , M. Buie
    • , C. Olkin
    • , J. Parker
    • , S. Porter
    • , S. Robbins
    • , K. Singer
    • , C. Conrad
    • , C. Howett
    • , J. Kammer
    • , A. Parker
    • , E. Schindhelm
    • , A. Steffl
    • , H. Throop
    • , C. Tsang
    • , A. Zangari
    • , S. A. Stern
    • , C. B. Olkin
    •  & L. A. Young
  11. NASA Jet Propulsion Laboratory, Pasadena, California 91019, USA.

    • B. Buratti
    •  & K. Runyon
  12. Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20723, USA.

    • A. Cheng
    • , J. H. Roberts
    • , H. Weaver
    • , O. Barnouin
    • , C. Lisse
    • , A. Marcotte
    • , M. Saina
    • , H. Winters
    •  & H. A. Weaver
  13. Southwest Research Institute, San Antonio, Texas 78238, USA.

    • R. Gladstone
    •  & K. Retherford
  14. Lowell Observatory, Flagstaff, Arizona 86001, USA.

    • W. Grundy
  15. University of Virginia, Charlottesville, Virginia 22904, USA.

    • A. D. Howard
    •  & A. Verbiscer
  16. National Optical Astronomy Observatory, Tucson, Arizona 85719, USA.

  17. Stanford University, Stanford, California 94305, USA.

    • I. Linscott
    •  & L. Tyler
  18. Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, California 95064, USA.

    • Francis Nimmo
  19. B612 Foundation, Mill Valley, California 94941, USA.

    • T. Lauer
    •  & H. Reitsema
  20. NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.

    • D. Reuter
  21. Lunar and Planetary Institute, Houston, Texas 77058, USA.

    • P. M. Schenk
  22. The SETI Institute, Mountain View, California 94043, USA.

    • M. Showalter
  23. The Johns Hopkins University, Baltimore, Maryland 21218, USA.

    • D. Strobel
  24. George Mason University, Fairfax, Virginia 22030, USA.

    • M. Summers
  25. Planetary Science Institute, Tucson, Arizona 85719, USA.

    • M. Banks
  26. University of Arizona, Tucson, Arizona 85721, USA.

    • V. Bray
  27. Cornell University, Ithaca, New York 14853, USA.

    • B. Carcich
    •  & J. Hofgartner
  28. Arlington, Vermont 05250, USA.

    • A. Chaikin
  29. University of Maryland, College Park, Maryland 20742, USA.

    • D. Hamilton
  30. Space Telescope Science Institute, Baltimore, Maryland 21218, USA.

    • J. Stansberry
  31. Roane State Community College, Oak Ridge, Tennessee 37830, USA.

    • T. Stryk
  32. Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

    • R. P. Binzel
    •  & A. Earle

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Contributions

W.B.M. led the study and wrote the paper, with substantial input from F.N.; T.W. and J.H.R. performed the CitCom finite element convection calculations; P.M.S. developed the software to create stereographic and photoclinometric digital elevation models (DEMs) using New Horizons LORRI and MVIC images, and created the preliminary DEM for SP; O.L.W. mapped the SP region using New Horizons images in ArcGIS; J.M.M., J.R.S., A.D.H, O.M.U. and S.A.S. contributed to the understanding of the multiple roles N2 ice plays in the geology of SP and its environs. S.A.S., H.A.W., C.B.O., L.A.Y. and K.E.S. are the lead scientists of the New Horizons project. The entire Geology, Geophysics, and Imaging Theme Team (listed) contributed to the success of the Pluto encounter.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to William B. McKinnon.

All spacecraft data and higher-order products presented in this Letter will be delivered to NASA’s Planetary Data System (https://pds.nasa.gov) in a series of stages in 2016 and 2017 because of the time required to fully downlink and calibrate the data set.

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DOI

https://doi.org/10.1038/nature18289

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