DPS 2001 meeting, November 2001
Session 48. Mars Surface
Oral, Chairs: N. Barlow, J. Bell III, Friday, November 30, 2001, 4:30-6:40pm, Regency E

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[48.05] High Resolution Imaging Spectroscopy of Mars using HST/STIS during 1999 and 2001

J.F. Bell III (Cornell Univ., Dept. of Astronomy), M.J. Wolff (Space Sci. Inst.), J. Sohl-Dickstein (Cornell), R.V. Morris (NASA/JSC)

We have used the Hubble Space Telescope (HST) and the Space Telescope Imaging Spectrograph (STIS) instrument to perform high resolution imaging spectroscopy of Mars during the 1999 and 2001 oppositions. Our 1999 observations were obtained using the G750L grating, covering 530 to 1030 nm at 0.48 nm/channel. The STIS 0.2\arcsec slit was pushbroom-scanned across the 16.2\arcsec diameter planet in 70 adjacent steps , yielding a 3-dimensional image cube in 1021 wavelengths and at ~20\times80 km spatial resolution per spectrum. This sequence was executed during four visits spaced ~90{\circ} apart in Martian longitude on 1999 April 27, May 1, 6, and 7 (Ls=130{\circ} to 135{\circ}). Each slit image was calibrated to I/F and map-projected to yield a coregistered data set covering ~75% of the surface of Mars. Our 2001 observations utilized the same measurement strategy, but used the G430L grating to cover shorter wavelengths (270 to 590 nm at 0.27 nm/channel). Because of the failure of the STIS side 1 electronics in May 2001, our measurements could not be obtained as planned near opposition in June 2001. Instead, we obtained our measurements once STIS side 2 was brought online, during four visits on 2001 August 9, 10, 14, and September 4 (Ls=211{\circ} to 227{\circ}). The planet ranged from 16.0\arcsec to 13.0\arcsec diameter over those dates, yielding spatial resolution and global coverage comparable to that obtained in 1999.

A primary goal of our study is to search for absorption features diagnostic of Fe2+ and Fe3+ minerals on Mars, and to map their spatial distribution. Our 1999 results focus on weak variations in spectral properties associated with albedo, geologic, and topographic variations, and comparisons to results from HST/WFPC2 imaging and MGS/TES spectroscopy. Initial results from our 2001 observations, obtained during one of the largest global dust storms of the last 30 years, focus mostly on the analysis of atmospheric aerosol physical and UV spectroscopic properties.

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