Mars: Narrow-Band Photometry, from 0.3 to 2.5 Microns, of Surface Regions during the 1969 Apparition

Abstract

view Abstract Citations (88) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Mars: Narrow-Band Photometry, from 0.3 to 2.5 Microns, of Surface Regions during the 1969 Apparition McCord, Thomas B. ; Westphal, James A. Abstract Narrow-band spectrophotometric observations were made of areas on Mars 200 km in diameter and of the whole disk of Mars during the 1969 apparition. The spectral region from 0.3 to 2.5 was covered with a resolution of 0.02-0.07 . The spectral reflectivities of six Martian areas relative to the bright region Arabia were obtained near opposition. Syrtis Major and Arabia were also observed before opposition. Geometric albedos have been calculated for five areas between 0.3 and 1.1 and for two additional areas and the whole disk of Mars between 0.3 and 2.5 , . Martian bright areas are very red in color, reaching a maximum geometric albedo of 0.42 in the near-infrared; dark areas are less red. Absorption features appear in the spectral reflectivity curves at 0.95 for biight regions and at 1.00 for dark regions. Absorption features which differ between Arabia and Syrtis Major appear in the relative reflection spectra near the position of the absorption bands of water and water ice. There seems to be a spectrum of Martian spectral reflectivity properties in which the bright area Arabia and the dark area Syrtis Major (of the areas observed) represent the end members. Between March and May 1969, Arabia became brighter and redder but the spectral reflectivity of Syrtis Major remained the same, in conflict with traditional seasonal "darkening wave" observations. A difference of the scattering properties with solar phase angle for bright and dark regions may exist. Limb darkening increases from near zero at about 0.42 to a maximum near 1 M, and remains about constant beyond I . The albedo of a small area at the center of the Martian disk reaches 1.6 times the average of the Martian disk at 1 . Publication: The Astrophysical Journal Pub Date: August 1971 DOI: 10.1086/151069 Bibcode: 1971ApJ...168..141M full text sources ADS |