CDROM/ICARUS/V111/P106 2.0 to 2.4 um Spectroscopy of Mars (Bell+ 1994) ================================================================================ Spectroscopy of Mars from 2.04 to 2.44 um During the 1993 Opposition: Absolute Calibration and Atmospheric vs Mineralogic Origin of Narrow Absorption Features James F. Bell III, James B. Pollack, Thomas R. Geballe, Dale P. Cruikshank, & Richard Freedman <1994, Icarus, 111, 106> =1994Icar..111..106B ================================================================================ Abstract: We present moderate-resolution (lambda/delta(lambda) = 300 to 370) reflectance spectra of Mars from 2.04 to 2.44 um 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, 2.331 +/- 0.001, and 2.357 +/- 0.002 um). Two of the bands (2.331 +/- 0.001 and 2.357 +/- 0.002 um) 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 bands centered at 2.278 +/- 0.002 and 2.296 +/- 0.002 um 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 bonds 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. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table3.dat 95 50 1993 CGS4 Mars data observational and physical parameters *.rf 35 . 2.04 to 2.44 um spectra as defined in Table 3 mars1_3.rfs 49 176 Spectrum 1.3, scaled to 1.0 at 2.286 then smoothed -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 A4 --- SpNo *Spectrum number 5- 6 2X --- --- Blank 7-13 A7 --- FileNo File number 14-20 F7.1 deg Lat_Avg Average latitude of spectrum 21-26 F6.1 deg Lat_Min Minimum latitude of spectrum 27-32 F6.1 deg Lat_Max Maximum latitude of spectrum 33-39 F7.1 deg Lon_Avg Average longitude of spectrum 40-45 F6.1 deg Lon_Min Minimum longitude of spectrum 46-51 F6.1 deg Lon_Max Maximum longitude of spectrum 52-57 F6.1 deg Inc_Avg Average incidence angle of spectrum 58-62 F5.1 deg Em_Avg Average emission angle of spectrum 63-68 F6.2 --- Alb_Avg Average Viking-IRTM broadband albedo of spectrum footprint 69-73 F5.1 km Topo_Avg Average Viking-derived topographic elevation of spectrum footprint 74-79 I6 km Diag Diagonal span of spectral footprint 80-84 I5 % Illum Percent of spectrum footprint that covers illuminated region of Mars 85-90 F6.1 mb P_GCM *Average surface pressure of spectrum footprint 91-95 I5 K T_GCM *Average surface temp. of spectrum footprint -------------------------------------------------------------------------------- Notes for file: table3.dat -------------------------------------------------------------------------------- SpNo: The spectrum number is in the form xx.y, where 1 <= xx <= 10 and 0 <= y <= 5. The spectra corresponding to these numbers can be found in files named marsxx_y.rf, where the xx and y are taken from this field. P_GCM, T_GCM: Predicted pressure and temperature, respectively, of each spectrum from the NASA-Ames low-dust GCM results appropriate for the season and time-of-day of these observations. -------------------------------------------------------------------------------- Byte-by-byte Description of files: *.rf -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 F8.6 um Lambda Wavelength 9-17 F9.5 --- Rad Radiance factor 18-26 F9.5 --- Prec Precision 27-35 F9.5 --- Acc Accuracy -------------------------------------------------------------------------------- Byte-by-byte Description of file: mars1_3.rfs -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 7 F7.5 um Lambda Wavelength 8-21 F14.6 --- Rad Radiance factor 22-35 F14.6 --- Prec Precision 36-49 F14.6 --- Acc Accuracy -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 07-May-95