Paper No. 48-2
COOK, J.C.1, SINGER, K.N.
2, CRUIKSHANK, D.P.
3, DALLE ORE, C.M.
4, ENNICO, K.
5, GRUNDY, W.M.
6, OLKIN, C.B.
7, PROTOPAPA, S.
8, STERN, S. Alan
7, WEAVER, H.A.
9, YOUNG, L.A.
10, SCHMITT, B.
11, PHILIPPE, S.
11, STANSBERRY, J.A.
12, BINZEL, R.P.
13, EARLE, A.M.
13, HOWETT, C.J.Α.
10, PARKER, A.H.
10, VERBISCER, A.J.
14, REUTER, D.C.
15, LUNSFORD, A.W.
15 and JENNINGS, D.E.
15, (1)unaffiliated, 10416 Garland Ln, Westminster, CO 80021, (2)Southwest Research Institute, 1050 Walnut St., Suite 300, Boulder, CO 80302, (3)NASA Ames Research Center, Moffett Field, CA 94035, (4)NASA Ames Research Center, Moffett Field, CA 94035; SETI Institute, Mountain View, CA, (5)NASA Ames Research Center, Moffett Field, CA, (6)Lowell Observatory, 1400 W. Mars Hill Rd., Flagstaff, AZ 86001, (7)Southwest Research Institute, Boulder, CO 80302, (8)University of Maryland, College Park, MD, (9)Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, (10)Southwest Research Institute, 1050 Walnut Street, Boulder, CO 80302, (11)Université Grenoble Alpes, CNRS, Grenoble, France, (12)Space Telescope Science Institute, Baltimore, MD, (13)Massachusetts Institute of Technology, Cambridge, MA 02139, (14)University of Virginia, Charlottesville, VA 22904, (15)NASA Goddard Space Flight Center, Greenbelt, MD, jccook@boulder.swri.edu
On July 14, 2015, New Horizons used its near-infrared spectral imager, LEISA (Linear Etalon Imaging Spectral Array, Reuter et al., 2008, Space Sci. Rev., 140, 129), to obtain two scans across the encounter hemisphere of Pluto at 6 to 7 km/pixel resolution. These observations mapped the distribution of N2, CH4, CO, and H2O-ice on Pluto’s surface (Grundy et al., 2016, Sci, 351, 9189; Protopapa et al., 2016, Icarus, in review). We have analyzed the H2O-ice-rich sites across the encounter hemisphere using Hapke theory.We find that H2O-ice does not appear in large quantities (>60%) above about 30◦N. In several locations, such as Viking Terra (all site names used are informal), H2O-ice appears to be an exposed bedrock layer. Along Virgil Fossa, H2O-ice appears to be exposed on the north facing scarp, coincident with the greatest elevation difference (1 to 1.5 km) between the north and south sides. H2O-ice appears for ∼40% of the full length of Virgil Fossa. This is in contrast to other regions of Virgil Fossa which appear to be H2O and CH4-ice poor (< 10-15% for each). The terrain to the north (∼50-75 km) and the south (<25 km) of Virgil Fossa nearest the H2O-ice has similar spectral properties (grain size and abundance) to the scarp, suggesting a relationship. Mass wasting may explain the exposure of H2O-ice along the scarp, but not in the surrounding area, especially on the higher, southern terrain.
Another site of interest is the region around Pulfrich Crater. The spectrum shows strong crystalline H2O-ice bands which is not centered on the crater. In addition, this site appears whitish in MVIC enhanced color images, while all other sites appear a distinct red/brown color. In the center of the H2O-ice-rich spot are a series of 3 or 4 east-west trending pits. Other similarly oriented pit chains in this region, some as close as 75 km away, lack the H2O-ice signature and appear to be rich in CH4-ice.
This work was supported by NASA’s New Horizons project.
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