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J. F. Bell III, T.H. McConnochie (Cornell), M.J. Wolff (SSI), D. Savransky, B. Stiglitz (Cornell), M. Malin (MSSS), P.R. Christensen, G.L. Mehall, L.L. Cherednik, K.C. Bender (ASU), THEMIS Science Team
The Mars Odyssey THEMIS instrument's Visible Imaging Subsystem (VIS) has been acquiring one to five color visible wavelength images of Mars at spatial scales of 18 to 72 m/pixel since February 2002. As of late-June 2003 VIS had acquired approximately 8600 image sequences covering approximately 9% of the Martian surface. Roughly two thirds of the VIS images acquired to date have been single-band images (mostly 654 nm); the remaining have been acquired in two or more bands, with most of those acquired through all five VIS filters (425, 540, 654, 749, and 860 nm). Nearly all of the two nominal MER landing ellipses have been imaged by VIS in at least the 654 nm band. We have developed a VIS calibration pipeline using pre-flight and in-flight calibration data to correct for instrumental effects and convert the images to radiance units. Five-color radiance data are also being used to generate true color composite views of VIS scenes. Work is also underway to quantify the surface vs. atmospheric components of the observed radiances using radiative transfer modeling and simultaneous MGS/TES and THEMIS/IRS observations. Initial analyses of the VIS multispectral data are focusing on the search for and identification of anomalous color units associated with intercrater deposits, dunes, wind streaks, and gullies. In general,we are finding that color variability is subtle on Mars even at the fine spatial scale of VIS observations. These results have important implications for testing of competing hypotheses dealing with weathering or alteration of the martian surface, as well as for planning of future MRO CRISM or HiRISE observations at higher spectral or spatial resolution.
This work is supported by the NASA Mars Odyssey Participating Scientist Program.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.