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Convection in a volatile nitrogen-ice-rich layer drives Pluto’s geological vigour

Nature volume 534, pages 82–85 (2016)Cite this article

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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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Figure 1: Image, topographic and map views of Sputnik Planum, Pluto.
Figure 2: High-resolution images of cellular terrain within SP.
Figure 3: Minimum thickness for convection in a layer of solid N2 ice on Pluto, as a function of basal temperature.
Figure 4: Example numerical model of N2 ice convection in SP.

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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

Author notes

  1. National Optical Astronomy Observatory, Tucson, Arizona 85719, USA.

Authors and Affiliations

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

    William B. McKinnon & Teresa Wong

  2. Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, 95064, California, USA

    Francis Nimmo

  3. Lunar and Planetary Institute, Houston, 77058, Texas, USA

    Paul M. Schenk

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

    Oliver L. White, J. M. Moore, O. M. Umurhan & K. E. Smith

  5. Johns Hopkins University Applied Physics Laboratory, Laurel, 20723, Maryland, USA

    J. H. Roberts & H. A. Weaver

  6. Southwest Research Institute, Boulder, 80302, Colorado, USA

    J. R. Spencer, S. A. Stern, C. B. Olkin & L. A. Young

  7. Department of Environmental Sciences, University of Virginia, Charlottesville, 22904, Virginia, 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, 63130, Missouri, USA

    W. B. McKinnon

  10. Southwest Research Institute, Boulder, 80302, Colorado, 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, 91019, California, USA

    B. Buratti & K. Runyon

  12. Johns Hopkins University Applied Physics Laboratory, Laurel, 20723, Maryland, 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, 78238, Texas, USA

    R. Gladstone & K. Retherford

  14. Lowell Observatory, Flagstaff, 86001, Arizona, USA

    W. Grundy

  15. University of Virginia, Charlottesville, 22904, Virginia, USA

    A. D. Howard & A. Verbiscer

  16. Stanford University, Stanford, 94305, California, USA

    I. Linscott & L. Tyler

  17. Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, 95064, California, USA

    Francis Nimmo

  18. B612 Foundation, Mill Valley, 94941, California, USA

    T. Lauer & H. Reitsema

  19. NASA Goddard Space Flight Center, Greenbelt, 20771, Maryland, USA

    D. Reuter

  20. Lunar and Planetary Institute, Houston, 77058, Texas, USA

    P. M. Schenk

  21. The SETI Institute, Mountain View, 94043, California, USA

    M. Showalter

  22. The Johns Hopkins University, Baltimore, 21218, Maryland, USA

    D. Strobel

  23. George Mason University, Fairfax, 22030, Virginia, USA

    M. Summers

  24. Planetary Science Institute, Tucson, 85719, Arizona, USA

    M. Banks

  25. University of Arizona, Tucson, 85721, Arizona, USA

    V. Bray

  26. Cornell University, Ithaca, 14853, New York, USA

    B. Carcich & J. Hofgartner

  27. Arlington, 05250, Vermont, USA

    A. Chaikin

  28. University of Maryland, College Park, 20742, Maryland, USA

    D. Hamilton

  29. Space Telescope Science Institute, Baltimore, 21218, Maryland, USA

    J. Stansberry

  30. Roane State Community College, Oak Ridge, 37830, Tennessee, USA

    T. Stryk

  31. Massachusetts Institute of Technology, Cambridge, 02139, Massachusetts, USA

    R. P. Binzel & A. Earle

Authors
  1. William B. McKinnon
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  3. Teresa Wong
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  4. Paul M. Schenk
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  5. Oliver L. White
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  6. J. H. Roberts
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  7. J. M. Moore
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  15. K. E. Smith
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Consortia

the New Horizons Geology, Geophysics and Imaging Theme Team

  • J. M. Moore
  • , W. B. McKinnon
  • , J. R. Spencer
  • , R. Beyer
  • , M. Buie
  • , B. Buratti
  • , A. Cheng
  • , D. Cruikshank
  • , C. Dalle Ore
  • , R. Gladstone
  • , W. Grundy
  • , A. D. Howard
  • , T. Lauer
  • , I. Linscott
  • , Francis Nimmo
  • , C. Olkin
  • , J. Parker
  • , S. Porter
  • , H. Reitsema
  • , D. Reuter
  • , J. H. Roberts
  • , S. Robbins
  • , P. M. Schenk
  • , M. Showalter
  • , K. Singer
  • , D. Strobel
  • , M. Summers
  • , L. Tyler
  • , H. Weaver
  • , O. L. White
  • , O. M. Umurhan
  • , M. Banks
  • , O. Barnouin
  • , V. Bray
  • , B. Carcich
  • , A. Chaikin
  • , C. Chavez
  • , C. Conrad
  • , D. Hamilton
  • , C. Howett
  • , J. Hofgartner
  • , J. Kammer
  • , C. Lisse
  • , A. Marcotte
  • , A. Parker
  • , K. Retherford
  • , M. Saina
  • , K. Runyon
  • , E. Schindhelm
  • , J. Stansberry
  • , A. Steffl
  • , T. Stryk
  • , H. Throop
  • , C. Tsang
  • , A. Verbiscer
  • , H. Winters
  • , A. Zangari
  • , R. P. Binzel
  • , A. Earle
  • , S. A. Stern
  • , H. A. Weaver
  • , C. B. Olkin
  • , L. A. Young
  •  & K. E. Smith

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.

Corresponding author

Correspondence to William B. McKinnon.

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Competing interests

The authors declare no competing financial interests.

Additional information

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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McKinnon, W., Nimmo, F., Wong, T. et al. Convection in a volatile nitrogen-ice-rich layer drives Pluto’s geological vigour. Nature 534, 82–85 (2016). https://doi.org/10.1038/nature18289

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