GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 48-3
Presentation Time: 2:10 PM


GRUNDY, W.M.1, BERRY, K.L.2, BEYER, R.A.3, BINZEL, R.P.4, BRAY, V.J.5, BUIE, M.W.6, BURATTI, B.J.7, CHENG, A.C.8, COOK, J.C.9, CRUIKSHANK, D.P.3, DALLE ORE, C.M.10, EARLE, A.M.4, ENNICO, K.3, JENNINGS, D.E.11, HOWETT, C.J.Α.6, KAISER, R.I.12, LAUER, T.R.13, LINSCOTT, I.R.14, LISSE, C.M.8, LUNSFORD, A.W.11, MCKINNON, W.B.15, MOORE, J.M.3, NIMMO, F.16, OLKIN, C.B.6, PARKER, A.H.6, PARKER, J.Wm.6, PHILIPPE, S.17, PROTOPAPA, S.18, QUIRICO, E.17, REITSEMA, H.J.19, REUTER, D.C.11, ROBBINS, S.J.6, SCHENK, P.M.20, SCHMITT, B.17, SCIPIONI, F.3, SHOWALTER, M.R.21, SINGER, K.N.6, SPENCER, J.R.6, STANSBERRY, J.A.22, STERN, S.A.6, TSANG, C.C.C.6, TYLER, G.L.14, UMURHAN, O.M.3, VERBISCER, A.J.23, WEAVER, H.A.8, WHITE, O.L.3, YOUNG, L.A.6 and ZANGARI, A.M.6, (1)Lowell Observatory, 1400 W. Mars Hill Rd., Flagstaff, AZ 86001, (2)Northern Arizona University and United States Geological Survey, Flagstaff, AZ, (3)NASA Ames Research Center, Moffett Field, CA 94035, (4)Massachusetts Institute of Technology, Cambridge, MA 02139, (5)Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, (6)Southwest Research Institute, 1050 Walnut Street, Boulder, CO 80302, (7)NASA Jet Propulsion Laboratory, La Cañada Flintridge, CA, (8)Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, (9)unaffiliated, 10416 Garland Ln, Westminster, CO 80021, (10)NASA Ames Research Center, Moffett Field, CA 94035; SETI Institute, Mountain View, CA, (11)NASA Goddard Space Flight Center, Greenbelt, MD, (12)University of Hawai’i at Manoa, Honolulu, HI, (13)National Optical Astronomy Observatory, Tucson, AZ, (14)Stanford University, 350 Serra Mall, David Packard #319, Stanford, CA 94305, (15)Washington University, Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, One Brookings Drive, Saint Louis, MO 63130, (16)Department of Earth and Planetary Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, (17)Université Grenoble Alpes, CNRS, Grenoble, France, (18)University of Maryland, College Park, MD, (19)Ball Aerospace (retired), Boulder, CO, (20)Lunar and Planetary Institute, Houston, TX, (21)SETI Institute, Mountain View, CA, (22)Space Telescope Science Institute, Baltimore, MD, (23)University of Virginia, Charlottesville, VA 22904,

NASA's New Horizons probe explored the Pluto system in 2015. Its instrument suite recorded a trove of data for Pluto's large satellite Charon, most of which has now been transmitted back to Earth. The New Horizons observations revealed Charon to be a complex world in its own right. This talk will give an overview of what has been learned.

There is a striking dichotomy between Charon's smoother southern plains and more rugged northern hemisphere, with the boundary featuring a belt of tectonically broken terrain. These two major provinces are spectroscopically very similar in the near infrared, with H2O ice absorptions dominating the reflectance spectra in both areas. In the south, small wrinkles and pits hint at a cryovolcanic resurfacing episode. In the north, deep, but highly eroded chasms separate highland blocks, suggesting a global expansion early in Charon's history.

Impact craters are abundant across Charon's encounter hemisphere, but are not saturated, and craters smaller than ~10 km are relatively scarce. Craters exhibit a variety of albedo patterns in their ejecta with some having bright distil rays combined with darker inner ejecta. At least one crater shows an infrared absorption feature attributed to NH3ice, while other similar-looking craters do not.

Charon's northern polar region is distinctly dark and red compared with lower latitudes. The southern pole is similarly dark. The dark poles are interpreted as resulting from seasonal cold-trapping of escaping gas from Pluto's atmosphere, feeding photolytic production of heavier and less volatile molecules that go on to produce tholin-like macromolecular organics.

Charon's complexities suggest that comparably-sized objects elsewhere in the Kuiper belt are equally fascinating and worthy of exploration.

This work was supported by NASA’s New Horizons project.