Spectroscopy of Mars from 2.04 to 2.44μm during the 1993 Opposition: Absolute Calibration and Atmospheric vs Mineralogic Origin of Narrow Absorption Features

James F. Bell, James B. Pollack, Thomas R. Geballe, Dale P. Cruikshank, Richard Freedman

Research output: Contribution to journalArticle

29 Scopus citations

Abstract

We present moderate-resolution (λ/Δλ = 300 to 370) reflectance spectra of Mars from 2.04 to 2.44 μm that were obtained at UKIRT during the 1993 opposition. Seven narrow absorption features were detected and found to have a Mars origin. By comparison with solar and Mars atmospheric spectra, five of these features were attributed all or in part to Mars atmospheric CO2 or CO (2.052 ± 0.003, 2.114 ± 0.002, 2.150 ± 0.003, 2.37,1 ± 0.001, and 2.357 ± 0.002 ±m). Two of the bands (2,331 ± 0.001 and 2.357± 0.002 μm) appear to have widths and depths that are consistent with additional, nonatmospheric absorptions, although a solar contribution cannot be entirely ruled out. Two other weak hands centered at 2.278 ± 0.002 and 2.296 ± 0.002 μm may be at least partially mineralogic in origin. The data provide no conclusive identification of the mineralogy responsible for these absorption features. However, examination of terrestrial spectral libraries and previous moderate spectral resolution mineral studies indicates that the most likely origin of these features is either (bi)carbonate or (bi)sulfate anions in framework silicates or (Fe, Mg)-OH bends in sheet silicates. If the bands are caused by phyllosilicate minerals, then an explanation must be found for the extremely narrow widths of the cation-OH features in the Mars spectra as compared to terrestrial minerals.

Original languageEnglish (US)
Pages (from-to)106-123
Number of pages18
JournalIcarus
Volume111
Issue number1
DOIs
StatePublished - Sep 1994

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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