HR: 16:15h
AN: P24A-02    [Abstracts]
TI: Persistent summertime water ice deposits in the northern plains of Mars: Observations from MRO CRISM
AU: * Seelos, K D
EM: kim.seelos@jhuapl.edu
AF: JHU Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
AU: Seelos, F P
EM: frank.seelos@jhuapl.edu
AF: JHU Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
AU: Murchie, S L
EM: scott.murchie@jhuapl.edu
AF: JHU Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
AU: Titus, T N
EM: ttitus@usgs.gov
AF: USGS, 2255 N. Gemini Drive, Flagstaff, AZ 86001,
AU: CRISM Team, T
AB: Analysis of MRO CRISM multispectral mapping data obtained during the late northern summer season on Mars (Ls = 130-180 degrees) reveals small water ice deposits distributed throughout the northern plains at latitudes quite distant from the residual polar cap. These outliers range in size from a few hundreds of meters to several kilometers, and are generally associated with the northward facing slopes of crater rims or other elevated landforms. In a few instances the ice deposits are located on the leeward (southeast-facing) sides of larger craters, and may indicate the presence of wintertime CO₂ frost formation from orographic lifting. The brighter frost sublimes more slowly than the surrounding CO₂ ice, ultimately forming a late spring cold trap and inducing an accumulation of water ice. During the first 4 months of MRO primary science phase (PSP), CRISM was able to cover ~75% of the northern plains surface (at 75 degrees latitude) with 73 channel visible/near infrared (0.41 to 3.92 μm) multispectral data as part of its systematic global mapping campaign. These long, 10 km-wide strips of data are mosaicked together and resampled to 256 pix/deg (~231 m/pix) spatial resolution. CRISM's wavelength range is particularly well-suited to distinguishing between different types and grain sizes of CO₂ and water ice, as well as iron- bearing minerals, sulfates, and phyllosilicates. False color composites of the multispectral data allow consistent mapping of the lowest latitudes of water ice occurrences and comparison to other global datasets. The average minimum latitude that water ice is observed during this time period is 75.5 degrees, with excursions of up to 10 degrees. Albedo appears to be a secondary control after local slope, and large scale topographic trends do not influence the locations of residual ice patches. Further comparison to Mars Odyssey GRS inferred subsurface water ice distribution may provide important clues regarding subsurface-surface-atmospheric volatile interactions and the global water budget on Mars.
DE: 5422 Ices
DE: 5462 Polar regions
DE: 5464 Remote sensing
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting