HR: 14:25h
AN: P12C-04 INVITED     [PDF]
TI: Synthesis of Spectral Data From the Grey Hematite Regions of Mars
AU: * Calvin, W
EM: wcalvin@unr.edu
AF: Geological Sciences, MS172, University of Nevada, Reno, NV 89557
AU: Fallacaro, A
EM: fallacar@unr.edu
AF: Geological Sciences, MS172, University of Nevada, Reno, NV 89557
AU: Baldridge, A
AF: Geological Sciences, Arizona State University, Tempe, AZ 85287
AB: The martian surface has been mapped by a number of visible and infrared spectral instruments from orbit. Telescopic and historical data sets noted the global albedo distribution of bright and dark units. Work in the near infrared (1 to 5 $\mu$m) identified subtle spectral variations and the appearance of areas with unique signatures. Broad classification of color and near-infrared spectral units include bright ferric material (dust), dark ferrous material (mafic rocks and pyroxene), dark ``crystalline'' ferric material (low albedo but with strong ferric absorptions) and water of hydration in surface materials. The Thermal Emission Spectrometer (TES) on MGS has identified two dominant surface units (mafic/basaltic and basaltic/andesitic-or-glassy-or-weathered). Small outcrops where the spectral signature of bulk grey hematite is exposed at the surface have been identified in Meridiani, Aram Chaos and Valles Marineris. Data from both the Infrared Spectrometers (IRS) on Mariner 6 and 7 and the Imaging Spectrometer for Mars (ISM) show the hematite locations to be more hydrated than other surface regions. Initial comparisons between ISM and the Gamma Ray Spectrometer (GRS) on Odyssey show the increased infrared signature of water in regions also found by GRS to contain more hydrogen. The GRS also shows a broad enhancement of hydrogen over Meridiani and Arabia which covers the hematite outcrop but is much larger in extent. This can be explained if GRS is sensitive both to surface hydration and water at depth in minerals or ice. The preferred interpretation for the bulk hematite units is an aqueous precipitate and synthesis of multiple spectral data sets support that conclusion. A synthesis of the data from these instruments at the hematite locations will be presented. The largest of the sites, in Terra Meridiani, is the landing site for the ``Opportunity'' Mars Exploration Rover which lands Jan 25, 2004. Consideration of constraints imposed by these orbital data sets suggests either ground water or sub-aqueous formation mechanisms and hypotheses for both can be tested at the rover site. The Athena Science instrument suite will provide new information to be integrated with data from orbit to constrain the origins of these units.
DE: 5410 Composition
DE: 5464 Remote sensing
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting