The Charon-forming giant impact as a source of Pluto’s dark equatorial regions

Abstract

Pluto exhibits complex regional diversity in its surface materials1,2. One of the most striking features is the dark reddish material, possibly organic matter, along Pluto’s equator coexisting with the H2O-rich crust2. Little is known, however, about the surface process responsible for the dark equatorial regions. Here, we propose that Pluto’s dark regions were formed through reactions in elongated pools of liquid water near the equator, generated by the giant impact that formed Charon35. Our laboratory experiments show that dark reddish organic matter, comparable to Pluto’s dark materials, is produced through polymerization of simple organic compounds6,7 that would have been present in proto-Pluto (for example, formaldehyde) by prolonged heating at temperatures ≥50 °C. Through hydrodynamic impact simulations, we demonstrate that an impactor, one-third the mass of Pluto, colliding with proto-Pluto—with an interior potential temperature of 150–200 K—could have generated both a Charon-sized satellite and high-temperature regions around Pluto’s equator. We also propose that high-velocity giant impacts result in global or hemispherical darkening and reddening, suggesting that the colour variety of large Kuiper belt objects812 could have been caused by frequent, stochastic giant impacts in a massive outer protoplanetary disk in the early Solar System1316.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Visible transmittance spectra and visual appearance of solutions after heating.
Figure 2: Formation of a Charon-sized satellite and elongated post-impact heated area near Pluto’s equator.
Figure 3: Latitudinal distributions of heated-area fraction in the simulations, and observed dark-area fraction on Pluto.
Figure 4: Surface temperature distributions of the post-impact targets in the Mercator projection after high-velocity collisions.

References

  1. 1

    Stern, S. A. et al. The Pluto system: initial results from its exploration by New Horizons. Science 350, aad1815 (2015).

  2. 2

    Grundy, W. M. et al. Surface compositions across Pluto and Charon. Science 351, aad9189 (2016).

  3. 3

    McKinnon, W. B. On the origin of the Pluto–Charon binary. Astrophys. J. Lett. 344, L41–L44 (1989).

    Article  ADS  Google Scholar 

  4. 4

    Canup, R. M. A giant impact origin of Pluto–Charon. Science 307, 546–550 (2005).

    Article  ADS  Google Scholar 

  5. 5

    Canup, R. On a giant impact origin of Charon, Nix, and Hydra. Astron. J. 141, 35 (2011).

    Article  ADS  Google Scholar 

  6. 6

    Cody, G. D. Establishing a molecular relationship between chondritic and cometary organic solids. Proc. Natl Acad. Sci. USA 108, 19171–19176 (2011).

    Article  ADS  Google Scholar 

  7. 7

    Kebukawa, Y., Kilcoyne, A. L. D. & Cody, G. D. Exploring the potential formation of organic solids in chondrites and comets through polymerization of interstellar formaldehyde. Astrophys. J. 771, 19 (2013).

    Article  ADS  Google Scholar 

  8. 8

    Brown, M. E., Trujillo, C. A. & Rabinowitz, D. L. Discovery of a planetary-sized object in the scattered Kuiper belt. Astrophys. J. Lett. 635, L97–L100 (2005).

    Article  ADS  Google Scholar 

  9. 9

    Barucci, M. A. et al. (50000) Quaoar: surface composition variability. Astron. Astrophys. 584, A107 (2015).

    Article  Google Scholar 

  10. 10

    Barucci, M. A. (90377) Senda: investigation of surface compositional variation. Astrophys. J. 140, 2095–2100 (2010).

    Google Scholar 

  11. 11

    Lorenzi, V., Pinilla-Zlonso, N. & Licandro, J. Rotationally resolved spectroscopy of dwarf planet (136472) Makemake. Astron. Astrophys. 577, A86 (2015).

    Article  ADS  Google Scholar 

  12. 12

    De Bergh, C. et al. The surface of the transneptunian object 90482 Orcus. Astron. Astrophys. 437, 1115–1120 (2005).

    Article  ADS  Google Scholar 

  13. 13

    Stern, S. A. On the number of planets in the outer solar system: evidence of a substantial population of 1000-km bodies. Icarus 90, 271–281 (1991).

    Article  ADS  Google Scholar 

  14. 14

    Tsiganis, K., Gomes, R., Morbidelli, A. & Levision, H. F. Origin of the orbital architecture of the giant planets in the solar system. Nature 435, 459–461 (2005).

    Article  ADS  Google Scholar 

  15. 15

    Gomes, R., Levison, H. F., Tsiganis, K. & Morbidelli, A. Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets. Nature 435, 466–469 (2005).

    Article  ADS  Google Scholar 

  16. 16

    Levison, H. F., Morbidelli, A., VanLaerhoven, C., Gomes, R. & Tsiganis, K. Origin of the structure of the Kuiper belt during a dynamical instability in the orbits of Uranus and Neptune. Icarus 196, 258–273 (2008).

    Article  ADS  Google Scholar 

  17. 17

    Materese, C. K., Cruikshank, D. P., Sandford, S. A., Imanaka, H. & Nuevo, M. Ice chemistry on outer solar system bodies: electron radiolysis of N2-, CH4-, and CO- containing ices. Astrophys. J. 812, 150 (2015).

    Article  ADS  Google Scholar 

  18. 18

    Bottke, W. F., Vokrouhlický, D., Nesvorný, D. & Moore, J. M. Black rain: the burial of the Galilean satellites in irregular satellite debris. Icarus 223, 775–795 (2013).

    Article  ADS  Google Scholar 

  19. 19

    Moore, J. M. et al. The geology of Pluto and Charon through the eyes of New Horizons. Science 351, 1284–1293 (2016).

    Article  ADS  Google Scholar 

  20. 20

    McKinnon, W. B., Prialnik, D., Stern, S. A. & Coradini, A. In The Solar System Beyond Neptune (eds. Barucci, M. A., Boehnhardt, H., Cruikshank, D. P., Morbidelli, A. & Dotson, R. ) 213–241 (Univ. Arizona Press, 2008).

    Google Scholar 

  21. 21

    Mumma, M. J. & Charnley, S. B. The chemical composition of comets—emerging taxonomies and natal heritage. Ann. Rev. Astron. Astrophys. 49, 471–524 (2011).

    Article  ADS  Google Scholar 

  22. 22

    Protopapa, S. et al. Pluto’s global surface composition through pixel-by-pixel Hapke modeling of New Horizons Ralph/LEISA data. Preprint at http://arxiv.org/abs/1604.08468 (2016).

  23. 23

    Strazzulla, G., Massimino, P., Spinella, F., Calcagno, L. & Foti, A. M. IR spectra of irradiated organic materials. Infrared Phys. 28, 183–188 (1988).

    Article  ADS  Google Scholar 

  24. 24

    Court, R. W., Sephton, M. A., Parnell, J. & Gilmour, I. The alteration of organic matter in response to ionizing irradiation: chemical trends and implications for extraterrestrial sample analysis. Geochim. Cosmochim. Acta 70, 1020–1039 (2006).

    Article  ADS  Google Scholar 

  25. 25

    Kenyon, S. J. Planet formation in the outer solar system. Publ. Astron. Soc. Pacific 114, 265–283 (2002).

    Article  ADS  Google Scholar 

  26. 26

    Brown, M. E. et al. Satellites of the largest Kuiper belt objects. Astrophys. J. Lett. 639, L43 (2006).

    Article  ADS  Google Scholar 

  27. 27

    Barr, A. C. & Schwamb, M. E. Interpreting the densities of the Kuiper belt’s dwarf planets. Mon. Not. R. Astron. Soc. 460, 1542–1548 (2016).

    Article  ADS  Google Scholar 

  28. 28

    Pires, P. S., Winter, M. G. & Gomes, R. S. The evolution of a Pluto-like system during the migration of the ice giants. Icarus 246, 330–338 (2015).

    Article  ADS  Google Scholar 

  29. 29

    Currie, T. et al. Direct imaging and spectroscopy of a young extrasolar Kuiper belt in the nearest OB association. Astrophys. J. Lett. 807, L7 (2015).

    Article  ADS  Google Scholar 

  30. 30

    Bocklelée-Morvan, D., Crovisier, J., Mumma, M. J. & Weaver, H. A. In Comets II (eds Festou, M. C., Keller, H. U. & Weaver, H. A. ) 391–423 (Univ. Arizona Press, 2004).

    Google Scholar 

  31. 31

    Goesmann, F. et al. Organic compounds on comet 67P/Churyumov-Gerasimenko revealed by COSAC mass spectrometry. Science 349, aab0689 (2015).

    Article  Google Scholar 

  32. 32

    Lucy, L. B. A numerical approach to the testing of the fission hypothesis. Astron. J. 82, 1013–1024 (1977).

    Article  ADS  Google Scholar 

  33. 33

    Genda, H., Fujita, T., Kobayashi, H., Tanaka, H. & Abe, Y. Resolution dependence of disruptive collisions between planetesimals in the gravity regime. Icarus 262, 58–66 (2015).

    Article  ADS  Google Scholar 

  34. 34

    Genda, H., Kobayashi, H. & Kokubo, E. Warm debris disks produced by giant impacts during terrestrial planet formation. Astrophys. J. 810, 136 (2015).

    Article  ADS  Google Scholar 

  35. 35

    Stewart, S. T. & Ahrens, T. J. Shock Hugoniot of H2O ice. Geophys. Res. Lett. 30, 1332 (2003).

  36. 36

    Senft, L. E. & Stewart, S. T. Impact crater formation in icy layered terrains on Mars. Meteorit. Planet. Sci. 43, 1993–2013 (2008).

    Article  ADS  Google Scholar 

  37. 37

    Thompson, S. L. & Lauson, H. S. (eds) Improvements in the CHART D Radiation-Hydrodynamic Code III: Revised Analytic Equations of State (Sandia National Laboratories, 1972).

    Google Scholar 

  38. 38

    Melosh, H. J. A hydrocode equation of state for SiO2 . Meteorit. Planet. Sci. 42, 2079–2098 (2007).

    Article  ADS  Google Scholar 

  39. 39

    Genda, H., Kokubo, E. & Ida, S. Merging criteria for giant impacts of protoplanets. Astrophys. J. 744, 137 (2012).

    Article  ADS  Google Scholar 

  40. 40

    Cheng, W. H., Lee, M. H. & Peale, S. J. Complete tidal evolution of Pluto–Charon. Icarus 233, 242–258 (2014).

    Article  ADS  Google Scholar 

  41. 41

    Monaghan, J. J. Smoothed particle hydrodynamics. Annu. Rev. Astron. Astrophys. 30, 543–574 (1992).

    Article  ADS  Google Scholar 

  42. 42

    Monaghan, J. J. & Lattanzio, J. C. A refined particle method for astrophysical problems. Astron. Astrophys. 149, 135–143 (1985).

    MATH  ADS  Google Scholar 

  43. 43

    Barr, A. C. & Canup, R. M. Constraints on gas giant satellite formation from the interior states of partially differentiated satellites. Icarus 198, 163–177 (2008).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

Y.S. thanks S. Tachibana for providing the methods to produce the organic matter from formaldehyde solution. This study was supported by Grant-in-Aids for Scientific Research from the Japan Society for Promotion of Science (26707024, 16001111, 16K13873 and 15K13562), from the JGC-S Scholarship Foundation, and from the Astrobiolgy Center of the National Institutes of Natural Sciences (NINS).

Author information

Affiliations

Authors

Contributions

Y.S. developed the idea for the study, and Y.S. and T.F. performed the experiments. H.G. performed hydrodynamic simulations. S.K. performed interior temperature calculation and image analysis. All the authors contributed to the interpretation of the results.

Corresponding author

Correspondence to Yasuhito Sekine.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Table 1, Supplementary Figures 1–10. (PDF 2724 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Sekine, Y., Genda, H., Kamata, S. et al. The Charon-forming giant impact as a source of Pluto’s dark equatorial regions. Nat Astron 1, 0031 (2017). https://doi.org/10.1038/s41550-016-0031

Download citation

Further reading

  • Solar System Physics for Exoplanet Research

    • J. Horner
    • , S. R. Kane
    • , J. P. Marshall
    • , P. A. Dalba
    • , T. R. Holt
    • , J. Wood
    • , H. E. Maynard-Casely
    • , R. Wittenmyer
    • , P. S. Lykawka
    • , M. Hill
    • , R. Salmeron
    • , J. Bailey
    • , T. Löhne
    • , M. Agnew
    • , B. D. Carter
    •  & C. C. E. Tylor

    Publications of the Astronomical Society of the Pacific (2020)

  • Stability of the subsurface ocean of pluto

    • Jun Kimura
    •  & Shunichi Kamata

    Planetary and Space Science (2020)

  • On the origin & thermal stability of Arrokoth's and Pluto's ices

    • C.M. Lisse
    • , L.A. Young
    • , D.P. Cruikshank
    • , S.A. Sandford
    • , B. Schmitt
    • , S.A. Stern
    • , H.A. Weaver
    • , O. Umurhan
    • , Y.J. Pendleton
    • , J.T. Keane
    • , G.R. Gladstone
    • , J.M. Parker
    • , R.P. Binzel
    • , A.M. Earle
    • , M. Horanyi
    • , M. El-Maarry
    • , A.F. Cheng
    • , J.M. Moore
    • , W.B. McKinnon
    • , W.M. Grundy
    • , J.J. Kavelaars
    • , I.R. Linscott
    • , W. Lyra
    • , B.L. Lewis
    • , D.T. Britt
    • , J.R. Spencer
    • , C.B. Olkin
    • , R.L. McNutt
    • , H.A. Elliott
    • , N. Dello-Russo
    • , J.K. Steckloff
    • , M. Neveu
    •  & O. Mousis

    Icarus (2020)

  • Experimental and Simulation Efforts in the Astrobiological Exploration of Exooceans

    • Ruth-Sophie Taubner
    • , Karen Olsson-Francis
    • , Steven D. Vance
    • , Nisha K. Ramkissoon
    • , Frank Postberg
    • , Jean-Pierre de Vera
    • , André Antunes
    • , Eloi Camprubi Casas
    • , Yasuhito Sekine
    • , Lena Noack
    • , Laura Barge
    • , Jason Goodman
    • , Mohamed Jebbar
    • , Baptiste Journaux
    • , Özgür Karatekin
    • , Fabian Klenner
    • , Elke Rabbow
    • , Petra Rettberg
    • , Tina Rückriemen-Bez
    • , Joachim Saur
    • , Takazo Shibuya
    •  & Krista M. Soderlund

    Space Science Reviews (2020)

  • Atmospheric mass-loss from high-velocity giant impacts

    • Almog Yalinewich
    •  & Hilke Schlichting

    Monthly Notices of the Royal Astronomical Society (2019)

Search

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing