GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 48-5
Presentation Time: 2:45 PM


SINGER, Kelsi N.1, MCKINNON, William B.2, GREENSTREET, Sarah3, GLADMAN, Brett4, PARKER, Alex1, ROBBINS, Stuart J.5, SCHENK, Paul M.6, SPENCER, John R.5, STERN, S. Alan5, BRAY, Veronica J.7, WEAVER, Harold A.8, HOWARD, Alan D.9, YOUNG, Leslie A.10, OLKIN, Cathy5, ENNICO, Kimberly11, MOORE, Jeffrey12, BINZEL, Richard13 and TEAM, New Horizons Science5, (1)Southwest Research Institute, 1050 Walnut St #300, Boulder, CO 80302, (2)Washington University, Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, One Brookings Drive, Saint Louis, MO 63130, (3)Las Cumbres Observatory Global Telescope Network, Goleta, CA 93117, (4)University of British Columbia, Vancouver, BC BC V6T 1Z4, Canada, (5)Southwest Research Institute, Boulder, CO 80302, (6)Lunar and Planetary Institute, Universities Space Research Association, 3600 Bay Area Boulevard, Houston, TX 77058, (7)Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, (8)Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, (9)Department of Environmental Sciences, Univerisity of Virginia, PO Box 400123, Charlottesville, VA 22904-4123, (10)Southwest Research Institute, 1050 Walnut Street, Boulder, CO 80302, (11)NASA Ames Research Center, Space Science Division, MS-245-3, Moffett Field, CA 95129, (12)NASA Ames Research Center, MS-245-3, Moffett Field, CA 95129, (13)Massachusetts Institute of Technology, Cambridge, MA 02139,

Impact craters provide valuable clues for understanding the surface ages and geologic evolution of the Pluto system bodies. We will present crater mapping results from the best images from both the LORRI (LOng Range Reconnaissance Imager; Cheng et al., 2008, SSR, 140, 189-215) framing camera, and the Ralph/MVIC (Multispectral Visual Imaging Camera; Reuter et al., 2008, SSR, 140, 129-154; Howett et al., 2016, Icarus, under review) scanning imager. Pixels scales range from 77–850 m/px for Pluto and 154–865 m/px for Charon. Crater size frequency distributions have been derived for broad physiographic regions. No obvious secondary craters are observed on the encounter hemispheres of Pluto or Charon.

Pluto’s terrains display a diversity of crater retention ages and terrain types, indicating ongoing geologic activity and a variety of resurfacing styles including both exogenic and endogenic processes (Moore et al., 2016, Science, 351, 1284-1293). Charon’s informally named Vulcan Planum did experience early resurfacing, but crater densities suggest this is a relatively ancient surface, as are the northern terrains on Charon. The crater densities on Nix and Hydra indicate an old age similar to Charon’s (Weaver et al., 2016, Science, 351).

The crater size-frequency distributions for both Pluto and Charon break to shallower slope for craters smaller than 10 km in diameter. We observe this paucity of small craters (relative to a constant slope extrapolated from larger craters) on all terrains, despite adequate resolution to observe them. This lack of small craters cannot be explained by geological resurfacing alone. The lack of small craters on Pluto and Charon is more consistent with solar system formation models that result in fewer small impactors (e.g., Chiang and Youdin, 2010, AREPS, 38, 493-522; Nesvorny et al., 2010, AJ, 140, 785-793).

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