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The formation of Charon’s red poles from seasonally cold-trapped volatiles

2016; Nature Portfolio; Volume: 539; Issue: 7627 Linguagem: Inglês

10.1038/nature19340

1476-4687

W. M. Grundy, D. P. Cruikshank, G. R. Gladstone, C. J. A. Howett, Tod R. Lauer, J. R. Spencer, M. E. Summers, M. W. Buie, A. M. Earle, Kimberly Ennico, J. W. Parker, Simon B. Porter, K. N. Singer, S. A. Stern, A. Verbiscer, R. A. Beyer, Richard P. Binzel, B. J. Buratti, J. C. Cook, C. M. Dalle Ore, C. B. Olkin, A. H. Parker, S. Protopapa, É. Quirico, K. D. Retherford, S. J. Robbins, B. Schmitt, J. A. Stansberry, O. M. Umurhan, H. A. Weaver, L. A. Young, A. M. Zangari, V. J. Bray, A. F. Cheng, W. B. McKinnon, R. L. McNutt, J. M. Moore, F. Nimmo, Dennis C. Reuter, P. Schenk, S. A. Stern, F. Bagenal, Kimberly Ennico, G. R. Gladstone, W. M. Grundy, W. B. McKinnon, John M. Moore, C. B. Olkin, J. R. Spencer, H. A. Weaver, L. A. Young, T. Andert, O. S. Barnouin, R. A. Beyer, R. P. Binzel, M. K. Bird, V. J. Bray, M. Brozović, M. W. Buie, B. J. Buratti, A. F. Cheng, J. C. Cook, D. P. Cruikshank, C. M. Dalle Ore, A. M. Earle, H. A. Elliott, T. K. Greathouse, M. Hahn, D. P. Hamilton, M. E. Hill, D. P. Hinson, Jason D. Hofgartner, M. Horányi, A. D. Howard, C. J. A. Howett, Donald E. Jennings, Joshua A. Kammer, P. Kollmann, Tod R. Lauer, P. Lavvas, I. R. Linscott, C. M. Lisse, Allen Lunsford, D. J. McComas, R. L. McNutt, Max Mutchler, F. Nimmo, Jorge I. Núñez, M. Päetzold, A. H. Parker, J. W. Parker, Philippe Sylvain, M. Piquette, Simon B. Porter, S. Protopapa, É. Quirico, H. J. Reitsema, Dennis C. Reuter, S. J. Robbins, J. H. Roberts, Kirby Runyon, P. M. Schenk, Rebecca Schindhelm, B. Schmitt, M. R. Showalter, K. N. Singer, J. A. Stansberry, A. J. Steffl, D. F. Strobel, T. Stryk, M. E. Summers, J. R. Szalay, H. B. Throop, C. C. C. Tsang, G. L. Tyler, O. M. Umurhan, A. Verbiscer, M. H. Versteeg, Gerald Weigle, O. L. White, W. W. Woods, E. F. Young, A. M. Zangari,

Atmospheric Ozone and Climate

The unusual dark red coloration of Charon's northern polar cap is shown to be produced from hydrocarbons that are cold-trapped from Pluto's escaping atmosphere during winter. Will Grundy et al. report New Horizons images of the southern hemisphere of Pluto's large satellite Charon illuminated by Pluto-shine, and images taken during the approach phase showing the northern polar cap over a range of longitudes. They also model the surface thermal environment on Charon. The model results are consistent with the suggestion that the unusual dark red coloration of Charon's northern polar cap is the result of hydrocarbons that are cold-trapped from Pluto's escaping atmosphere during winter. A unique feature of Pluto's large satellite Charon is its dark red northern polar cap1. Similar colours on Pluto's surface have been attributed2 to tholin-like organic macromolecules produced by energetic radiation processing of hydrocarbons. The polar location on Charon implicates the temperature extremes that result from Charon's high obliquity and long seasons in the production of this material. The escape of Pluto's atmosphere provides a potential feedstock for a complex chemistry3,4. Gas from Pluto that is transiently cold-trapped and processed at Charon's winter pole was proposed1,2 as an explanation for the dark coloration on the basis of an image of Charon's northern hemisphere, but not modelled quantitatively. Here we report images of the southern hemisphere illuminated by Pluto-shine and also images taken during the approach phase that show the northern polar cap over a range of longitudes. We model the surface thermal environment on Charon and the supply and temporary cold-trapping of material escaping from Pluto, as well as the photolytic processing of this material into more complex and less volatile molecules while cold-trapped. The model results are consistent with the proposed mechanism for producing the observed colour pattern on Charon.