Submillimeter Wave Astronomy Satellite observations of the Martian atmosphere:: Temperature and vertical distribution of water vapor

We report the first detections of absorption features in the submillimeter spectrum of Mars that are due to the H2O (1(10)-1(01)) and (CO)-C-13 (5-4) rotational transitions. Observations were obtained over several days near the planet's closest approach to Earth in 1999 April. These observations simultaneously provide us with an opportunity to derive the atmospheric temperature structure and to measure directly the distribution of water vapor with altitude. The Martian atmosphere is found to be relatively cool, consistent with results found from ground-based millimeter observations of CO. The distribution of water in the Martian atmosphere matches a profile of constant, 100% saturation from 10 to 45 km altitude.