High Spatial Resolution near-IR Imaging Spectroscopy of Mars from the IRTF During 1996-97

J.F. Bell III, D.R. Klassen, J.E. Moersch (Cornell), W.F. Golisch, D.M. Griep, C.D. Kaminski (NASA IRTF), P. Martin, C. Dumas (U. Hawaii), R.N. Clark (USGS), E.A. Cloutis (U. Winnepeg)

We carried out a program of near-IR telescopic observations of Mars during the 1996-97 opposition using the NSFCAM 256 tex2html_wrap_inline13 256 InSb array camera at the NASA IRTF on Mauna Kea. Our observations were obtained on 10 full or partial observing nights between December 1996 and May 1997, corresponding to mid northern spring to mid northern summer on Mars. We obtained Nyquist-sampled CVF images of Mars in 105 wavelengths across the K and L bands on most of the nights. In order to maximize the spatial resolution, we also obtained thousands of very short exposure time speckle images in each wavelength; typically one or two of the 50 to 100 images obtained at each CVF position have a spatial resolution approaching the diffraction limit of the IRTF ( tex2html_wrap_inline15 100 km/pixel at 2.3 tex2html_wrap_inline17 m). The best image at each wavelength is used to preserve the spatial information, and the rest of the speckle images at each wavelength are used to calculate a corresponding variance image for SNR determination and error propagation. The images are registered via map projection and assembled into 3-dimensional image cubes (spatial tex2html_wrap_inline13 spatial tex2html_wrap_inline13 spectral) for analysis.

These data provide information on the behavior of Mars surface and atmospheric volatiles via the detection and spatial mapping of spectral features near 2.0, 2.4, 3.0, and 3.6 tex2html_wrap_inline17 m in tex2html_wrap_inline25 ice, near 2.0 and 3.33 tex2html_wrap_inline17 m in tex2html_wrap_inline29 ice, and in the extended 2.5 to 3.2 tex2html_wrap_inline17 m region in hydrated minerals. The data also allow for sensitive spectral searches of climatically-diagnostic surface minerals like carbonates, sulfates, clays, and organics because the spectral coverage was designed to coincide with the positions of diagnostic absorption features in those materials. Particular emphasis was placed on measurements of the Acidalia hemisphere in order to complement planned Mars Pathfinder visible wavelength data and Palomar and MGS/TES thermal IR spectra of this region.