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Spectral Anomalies in the 11 and 12 micron Region From the Mariner Mars 7 Infrared SpectrometerTwo hundred-forty infrared spectra acquired by the 1969 Mariner Mars 7 Infrared Spectrometer (IRS), spanning the wavelength region 1.8-14.4 micron (5550-690/cm), have recently been recovered and calibrated in both wavelength and intensity. An examination of these IRS spectra has revealed absorptions at 11.25 and 12.5 micron that have not previously been reported for Mars. A search of the literature and spectral data bases shows that materials that exhibit a doublet at 11.25 and 12.5 micron are rare. In this paper we examine potential causes for these features and include a detailed discussion of carbonates, goethite, CO2 ice, and water ice. CO2 ice and water ice measured in transmission do not exhibit bands that match those recorded at 11.25 and 12.5 micron for Mars, which indicates that CO2 or water ice clouds are not the source of these features. Since these bands show no clear correlation with atmospheric path length, they are most likely caused by a surface material. In the IRS database they appear to be exceptionally intense in the western part of the Hellas basin. Goethite exhibits bands that are a good spectral match, but confirming whether goethite causes the features will require additional studies of the 20-50 micron region. These studies will require laboratory measurements of weathering coatings and an examination of spectra recorded of Mars by the 1971 Mariner Mars Infrared Interferometer Spectrometer (IRIS; 5-50 micron 2000200/cm) and the 1996 Thermal Emission Spectrometer (TES; 6-50 micron 1667-200/cm).
Document ID
20010019723
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Kirkland, Laurel E.
(Rice Univ. Houston, TX United States)
Herr, Kenneth C.
(Aerospace Corp. El Segundo, CA United States)
Date Acquired
August 20, 2013
Publication Date
September 25, 2000
Publication Information
Publication: Journal of Geophysical Research
Publisher: American Geophysical Union
Volume: 105
Issue: E9
ISSN: 0148-0227
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
Paper-1999JE001214
LPI-Contrib-1060
Funding Number(s)
CONTRACT_GRANT: NASW-4574
Distribution Limits
Public
Copyright
Other

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