Mars surface composition from reflectance spectroscopy: A summary
Visible and near-infrared (0.3--2.6 ..mu..m) reflectance spectra of the martian surface have been obtained primarily from earth-based telescopic observations, and multispectral images have been obtained both from spacecraft and earth-based observations. Observations in this wavelength region have confirmed the bimodal albedo distribution of surface materials, first observed visually. All spectra of Mars are characterized by strong Fe/sup 3 +/ absorptions from the near-UV to about 0.75 ..mu..m. Darker regions show this effect to a lesser degree, and are interpreted to be less oxidized materials. In addition, dark areas have Fe/sup 2 +/ absorptions near 1.0 ..mu..m, attributed primarily to olivines and pyroxenes. There is evidence at infrared wavelengths for highly dessicated mineral hydrates and for H/sub 2/O-ice and/or adsorbed H/sub 2/O. Observations of the north polar cap show a strong H/sub 2/O-ice spectral signature but no spectral evidence for CO/sub 2/-ice, while only CO/sub 2/-ice has been identified in spectra of the south polar cap. While the brightest materials on Mars are widespread and correlate with aeolian dust, darker materials show greater mineralogic variability and are thought to be closer in petrology and physical location to their parent rock. At present the best model for the dark materials is somewhat oxidized basaltic or ultramafic rock, regionally variable in composition and details of oxidation. The bright materials appear to be finer-grained assemblages of primarily highly oxygen-sharing dessicated mineral hydrate, some ferric oxides, and other less major constituents, including a small amount of relatively unaltered mafic material. The bright materials seem likely to be primary and/or secondary alteration products of the basaltic or ultramafic dark materials.
- Research Organization:
- Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii 96822
- OSTI ID:
- 5471849
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 84:B14
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
MARS PLANET
CHEMICAL COMPOSITION
SOILS
ALBEDO
CARBON DIOXIDE
ICE
INFRARED SPECTRA
REFLECTIVITY
VISIBLE SPECTRA
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
OPTICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PLANETS
SPECTRA
SURFACE PROPERTIES
640107* - Astrophysics & Cosmology- Planetary Phenomena