In July 2015, NASA’s New Horizons mission performed a flyby of Pluto, revealing details about the geology, surface composition and atmospheres of this world and its moons that are unobtainable from Earth. With a resolution as small as 80 metres per pixel, New Horizons’ images identified a large number of surface features, including a large basin filled with glacial ices that appear to be undergoing convection. Maps of surface composition show latitudinal banding, with non-volatile material dominating the equatorial region and volatile ices at mid- and polar latitudes. This pattern is driven by the seasonal cycle of solar insolation. New Horizons’ atmospheric investigation found the temperature of Pluto’s upper atmosphere to be much cooler than previously modelled. Images of forward-scattered sunlight revealed numerous haze layers extending up to 200 km from the surface. These discoveries have transformed our understanding of icy worlds in the outer Solar System, demonstrating that even at great distances from the Sun, worlds can have active geologic processes. This Review addresses our current understanding of the Pluto system and places it in context with previous investigations.
Subscribe to Journal
Get full journal access for 1 year
only $8.25 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Buratti, B. et al. Photometry of Pluto in the last decade and before: evidence for volatile transport? Icarus 162, 171–182 (2003).
Buratti, B. et al. Photometry of Pluto 2008–2014: evidence of ongoing seasonal volatile transport and activity. Astrophys. J. Lett. 804, L6–L12 (2015).
Buie, M. W. et al. Pluto and Charon with the Hubble Space Telescope. II. Resolving changes on Pluto’s surface and a map for Charon. Astron. J. 139, 1128–1143 (2010).
Buie, M. W. & Tholen, D. J. The surface albedo distribution of Pluto. Icarus 79, 23–37 (1989).
Buie, M. W. et al. in Pluto and Charon (eds Stern, S. A. & Tholen, D. J.) 269–293 (Univ. Arizona Press, Tucson, Arizona, 1997).
Tholen, D. J. & Buie, M. W. in Pluto and Charon (eds Stern, S. A. & Tholen, D. J.) 347–390 (Univ. Arizona Press, Tucson, Arizona, 1997).
Lellouch, E. et al. Pluto’s lower atmosphere structure and methane abundance from high-resolution spectroscopy and stellar occultations. Astron. Astrophys. 495, L17–L21 (2009).
Buie, M. W., Tholen, D. J. & Horne, K. Albedo maps of Pluto and Charon: initial mutual events results. Icarus 97, 211–227 (1992).
Young, E. F. et al. Mapping the variegated surface of Pluto. Astron. J. 117, 1063–1076 (1999).
Young, E. F., Binzel, R. P. & Crane, K. A two-color map of Pluto’s sub-Charon hemisphere. Astron. J. 121, 552–561 (2001).
Binzel, R. P. Hemispherical color differences on Pluto and Charon. Science 241, 1070–1072 (1988).
Albrecht, R. et al. High-resolution imaging of the Pluto–Charon system with the Faint Object Camera of the Hubble Space Telescope. Astrophys. J. 435, L75–L78 (1994).
Stern, S. A., Buie, M. W. & Trafton, L. M. HST high-resolution images and maps of Pluto. Astron. J. 113, 827–843 (1997).
Young, L. A. et al. New Horizons: anticipated scientific investigations at the Pluto system. Space Sci. Rev. 140, 93–127 (2008).
Buratti, B. et al. Global albedos of Pluto and Charon from LORRI New Horizons observations. Icarus 287, 207–217 (2017).
Moore, J. M. et al. The geology of Pluto and Charon through the eyes of New Horizons. Science 351, 1284–1293 (2016).
Hammond, N. P., Barr, A. C. & Parmentier, E. M. Recent tectonic activity on Pluto driven by phase changes in the ice shell. Geophys. Res. Lett. 43, 6775–6782 (2016).
Howard, A. D. et al. Pluto: pits and mantles on uplands north and east of Sputnik Planitia. Icarus 293, 218–230 (2017).
Johnson, B. C. et al. Formation of the Sputnik Planum basin and the thickness of Pluto’s subsurface ocean. Geophys. Res. Lett. 43, 10068–10077 (2016).
McKinnon, W. B. et al. Convection in a volatile nitrogen-rich-ice layer drives Pluto’s geologic vigour. Nature 534, 82–85 (2016).
White, O. L. et al. Geologic mapping of Sputnik Planitia on Pluto. Icarus 287, 261–286 (2017).
Hamilton, D. P. et al. The rapid formation of Sputnik Planitia early in Pluto’s history. Nature 540, 97–99 (2016).
Nimmo, F. et al. Global mean radius and shape of Pluto and Charon from New Horizons images. Icarus 287, 12–29 (2017).
Schenk, P. M. & Zahnle, K. On the negligible surface age of Triton. Icarus 192, 135–149 (2007).
Nimmo, F. & Spencer, J. R. Powering Triton’s recent geological activity by obliquity tides: implications for Pluto geology. Icarus 246, 2–10 (2015).
Beyer, R. A. et al. Charon tectonics. Icarus 287, 161–174 (2017).
Robbins, S. et al. Craters in the Pluto–Charon system. Icarus 287, 187–206 (2017).
Stern, S. A. et al. The Pluto system: initial results from its exploration by New Horizons. Science 350, 1815 (2015).
Rhoden, A. R. et al. The interior and orbital evolution of Charon as preserved in its geologic record. Icarus 246, 11–20 (2015).
Grundy, W. M. et al. Near-infrared spectral monitoring of Pluto’s ices: spatial distribution and secular evolution. Icarus 223, 710–721 (2013).
Prokhvatilov, A. I. & Yantsevich, L. D. X-ray investigation of the equilibrium phase diagram of CH4–N2 solid mixtures. Sov. J. Low Temp. Phys. 9, 94–98 (1983).
Grundy, W. M. et al. Surface compositions across Pluto and Charon. Science 351, aad9189 (2016).
Protopapa, S. et al. Pluto’s global surface composition through pixel-by-pixel Hapke modeling of New Horizons Ralph/LEISA data. Icarus 287, 218–228 (2017).
Schmitt, B. et al. Physical state and distribution of materials at the surface of Pluto from New Horizons LEISA imaging spectrometer. Icarus 287, 229–260 (2017).
Cruikshank, D. P., Imanaka, H. & Dalle Ore, C. M. Tholins as coloring agents on outer solar system bodies. Adv. Space Res. 36, 178–183 (2005).
Earle, A. et al. Long-term surface temperature modeling of Pluto. Icarus 287, 37–46 (2017).
Bertrand, T. & Forget, F. Observed glacier and volatile distribution on Pluto from atmosphere–topography processes. Nature 540, 86–89 (2016).
Cruikshank, D. et al. The surface compositions of Pluto and Charon. Icarus 246, 82–92 (2015).
Grundy, W. M. et al. The formation of Charon’s red poles from seasonally cold-trapped volatiles. Nature 539, 65–68 (2016).
Gladstone, G. R. et al. The atmosphere of Pluto as observed by New Horizons. Science 351, aad8866 (2016).
Cruikshank, D. P. et al. Pluto — evidence for methane frost. Science 194, 835–837 (1976).
Elliot, J. L. et al. Pluto’s atmosphere. Icarus 77, 148–170 (1989).
Elliot, J. L. et al. The recent expansion of Pluto’s atmosphere. Nature 424, 165–168 (2003).
Sicardy, B. et al. Large changes in Pluto’s atmosphere as revealed by recent stellar occultations. Nature 424, 168–170 (2003).
Olkin, C. B. et al. Evidence that Pluto’s Atmosphere does not collapse from occultations including the 2013 May 04 event. Icarus 246, 220–225 (2015).
Sicardy, B. et al. Pluto’s atmosphere from the 29 June 2015 ground-based stellar occultation at the time of the New Horizons’ flyby. Astrophys. J. Lett. 426, 220–225 (2016).
Young, L. A. et al. Detection of gaseous methane on Pluto. Icarus 127, 258–262 (1997).
Lellouch, E. et al. Detection of CO and HCN in Pluto’s atmosphere with ALMA. Icarus 286, 289–307 (2017).
Gao, P. et al. Constraints on the microphysics of Pluto’s photochemical haze from New Horizons observations. Icarus 287, 116–123 (2017).
Young, L. A. et al. Structure and composition of Pluto’s atmosphere from the New Horizons solar ultraviolet occultation. Icarus https://doi.org/10.1016/j.icarus.2017.09.006 (2017).
Wong, M. L. et al. The photochemistry of Pluto’s atmosphere as illuminated by New Horizons. Icarus 287, 110–115 (2017).
Sepan, R. et al. Preparing and implementing the New Horizons uplink occultations: applying concepts, tools, and lessons learned over nearly a decade of flight to achieve a successful operation. SpaceOps 2016 Conf. AIAA 2016–2537 (2016).
Hinson, D. P. et al. Radio occultation measurements of Pluto’s neutral atmosphere with New Horizons. Icarus 290, 96–111 (2017).
Gurrola, E. M. Interpretation of Radar Data from the Icy Galilean Satellites and Triton. PhD thesis, Stanford Univ. (1995).
Stern, A. S. et al. New Horizons constraints on Charon’s present day atmosphere. Icarus 287, 124–130 (2017).
Tombaugh, C. W. Reminiscences of the discovery of Pluto. Sky & Telescope 264–270 (March 1960).
Christy, J. W. & Harrington, R. S. The satellite of Pluto. Astron. J. 83, 1005–1008 (1978).
Christy, J. W. & Harrington, R. S. The discovery and orbit of Charon. Icarus 44, 38–40 (1980).
Weaver, H. A. et al. Discovery of two new satellites of Pluto. Nature 439, 943–945 (2006).
Showalter, M. R. et al. New satellite of (134340) Pluto: S/2011 (134340). Int. Astron. Union Circ. 9221 (2011).
Showalter, M. R. et al. New satellite of (134340) Pluto: S/2012 (134340). Int. Astron. Union Circ. 9253 (2012).
Weaver, H. A. et al. The small satellites of Pluto as observed by New Horizons. Science 351, 1281 (2016).
Binzel, R. P. et al. Climate zones on Pluto and Charon. Icarus 287, 30–36 (2017).
Stern, S. A. et al. Past epochs of significantly higher pressure atmospheres on Pluto. Icarus 287, 47–53 (2017).
This work was supported by the NASA New Horizons project. We thank the engineers and staff of the New Horizons team whose dedication enabled the initial reconnaissance of the Pluto system.
The authors declare no competing financial interests.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Olkin, C.B., Ennico, K. & Spencer, J. The Pluto system after the New Horizons flyby. Nat Astron 1, 663–670 (2017). https://doi.org/10.1038/s41550-017-0257-3