ISO observations of Mars: An estimate of the water vapor vertical distribution and the surface emissivity

Infrared spectra of Mars were taken with the two complementary spectrometer s onboard the European Space Agency's Infrared Space Observatory (ISO), in both moderate- and high-resolution mode. From the strengths of the observed water lines we derived information about the vertical distribution of wate r vapor and on the emissivity of the dust/surface system in the infrared. A ssuming atmospheric and surface temperatures derived from the European Mart ian Climate Database with a slight adjustment to the observed 15-mu m CO2 b and, the ISO data are consistent with an H2O mixing ratio of (3 +/- 1) x 10 (-4) at the surface, a saturation level at 13 +/- 2 km, and a total column density of 12 +/- 3.5 pr-mu m. The mean disk emissivity is found to be clos e to 1.0 at 6 mu m and 0.92 +/- 0.02 at 40 mu m. At longer wavelengths the emissivity decreases from a value of 0.97 +/- 0.03 at 50 mu m to 0.92 +/- 0 .03 at 180 mu m. (C) 2000 Academic Press.