HR: 16:50h
AN: P24A-05    [Abstracts]
TI: Bright Fans in Mars Cryptic Region Caused by Adiabatic Cooling of CO₂ Gas Jets.
AU: * Titus, T N
EM: ttitus@usgs.gov
AF: United States Geological Survey Astrogeology Team, 2255 North Gemini Drive, Flagstaff, AZ 86001, United States
AU: Kieffer, H H
EM: hkieffer@charter.net
AF: Celestrial Reasonings, 180 Snowshoe Lane P.O.Box 1057, Genoa, NV 89411-1057, United States
AU: Langevin, Y
EM: yves.langevin@ias.u-psud.fr
AF: IAS, CNRS / Universite Paris XI, Bat. 121, Orsay, 91405, France
AU: Murchie, S
EM: Scott.Murchie@jhuapl.edu
AF: Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, United States
AU: Seelos, F
EM: Frank.Seelos@jhuapl.edu
AF: Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, United States
AU: Vincendon, M
EM: mathieu.vincendon@ias.u-psud.fr
AF: IAS, CNRS / Universite Paris XI, Bat. 121, Orsay, 91405, France
AU: TEAM, C
EM: Scott.Murchie@jhuapl.edu
AF: Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, United States
AB: Over the last decade, observations of the retreat of the southern seasonal cap of Mars have revealed the presence of exotic processes within an area now informally referred to as the cryptic region. The appearance of dark spots, fans, blotches, and halos have been a "hot" topic of scientific discussion since they were first observed by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) [Malin et al., 1998]. Further observations by the Mars Odyssey (ODY) Thermal Emission Imaging System (THEMIS) showed that the dark features remained cold throughout the early-to-mid spring, suggesting that these features were either CO₂ ice or were in thermal contact with CO₂ ice [Kieffer et al., 2006]. In this paper, we present observations in the near-infrared at spatial resolutions that have previously been unavailable. We present further evidence that many of these features in the cryptic region are the result of cold jets, as first described by Kieffer [2000, 2007]. The adiabatic cooling of gas spewing downwind from the jets produces CO₂ frost, thus forming the bright fans. The bright fans appear to be devoid of H₂O ice, thus further supporting the hypothesis that they are formed from the downwind settling of CO₂ frost. In some areas, the bright fans are adjacent to dark fans and appear to start from common vertices, while in other areas, bright fan-like deposits occur without the strong presence of dark fans. References: Kieffer, H.H. (2000) Annual Punctuated CO₂ Slab-Ice and Jets on Mars, International Conference on Mars Polar Science and Exploration, p. 93. Kieffer, H.H. et al. (2006) Nature, 442,793-796. Kieffer, H.H. (2007) JGR, in press. Malin, M.C., M.H. Carr, G.E. Danielson, M.E. Davies, W.K. Hartmann, A.P. Ingersoll, P.B. James, H. Masursky, A.S. McEwen, L.A. Soderblom, P. Thomas, J. Veverka, M.A. Caplinger, M.A. Ravine, and T.A. Soulanille (1998) Early views of the Martian surface from the Mars orbiter camera of Mars global surveyor, Science, 279, 1681-1685.
DE: 5422 Ices
DE: 5462 Polar regions
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting