Results of TV imaging of Phobos (experiment VSK-FREGAT)

Abstract

From February to March 1989 the Phobos 2 spacecraft took 37 TV images of Phobos at a distance of 190–1100 km. These images complement Mariner-9 and Viking data by providing higherresolution coverage of a large region West of the crater Stickney (40–160°W) and by providing disk-resolved measurements of surface brightness at a greater range of wavelengths and additional phase angles. These images have supported updated mapping and characterization of large craters and grooves, and have provided additional observations of craters' and grooves' bright rims. Variations in surface visible/nearinfrared color ratio of almost a factor of 2 have been recognized ; these variations appear to be associated with the ejecta of specific large impact craters. Updated determinations of satellite mass and volume allow calculation of a more accurate value of bulk density, 1.90 ± 0.1 g cm^(−3). This is significantly lower than the density of meteoritic analogs to Phobos' surface, suggesting a porous interior perhaps containing interstitial ice.

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