DPS Meeting, Madison, October 1998
Session 22. Mars Surface II
Contributed Oral Parallel Session, Tuesday, October 13, 1998, 3:15-4:15pm, Madison Ballroom C

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[22.03] HST STIS and NICMOS Observations of Mars During 1997

J. F. Bell, III (Cornell Univ.), M. J. Wolff (Space Sciences Inst.), R. L. Comstock (Central Washington Univ.), P. B. James (Univ. Toledo)

We report initial results from the first observations of Mars using the two newest HST instruments: the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).

{\it STIS:} Long-slit STIS spectroscopic observations of Mars were made on 24 July 1997 UT. Our goal was to exploit the extremely high spatial resolution of HST to provide unique information on the mineralogy of the Martian surface to complement groundbased and spacecraft observations. STIS was configured with the G750L grating to cover the 550 to 1100 nm region at R=500 to 1000. A 0.2 arcsec slit was used to provide 200 km/pixel spatial resolution along-slit, and pushbroom scanning of the slit was planned to provide 200 km/pixel spatial resolution cross-slit. Due to an HST commanding error, however, the slit scan was not executed as programmed and the only valid data obtained are from a region along the limb of the planet. Nonetheless, reduction and calibration of these data show excellent consistency with decades of groundbased visible to near-IR spectroscopy of Mars, and reveal evidence for subtle spectral variations possibly caused by climatically-diagnostic iron-bearing minerals on the surface.

{\it NICMOS:} Narrowband filter NICMOS observations of Mars were made on 23 July 1997 UT (Ls=148\circ). The goal of these observations was to detect and spatially map surface and atmospheric volatiles and volatile-bearing minerals within a diagnostic wavelength region not covered by any currently-planned spacecraft instruments. Images were obtained through 11 NICMOS filters from 950 nm to 2370 nm using the NIC1 and NIC2 cameras, giving a maximum spatial resolution of 44 km/pixel. Coadding, dithering, and background removal enhanced the data quality. Initial reduction and calibration of these images reveals reflectance levels and spectral shape that are broadly consistent with previous WFPC2, groundbased, and Phobos-2 results. Although calibration refinements are continuing, initial analysis indicates variations in the abundance of surface hydrated minerals and of weakly altered iron-bearing mafic volcanics in the specific regions of Mars imaged (central longitude = 34\circW).

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