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 t he planet's closest approach to Earth in 1999 April. These observations sim ultaneously provide us with an opportunity to derive the atmospheric temper ature structure and to measure directly the distribution of water vapor wit h altitude. The Martian atmosphere is found to be relatively cool, consiste nt with results found from ground-based millimeter observations of CO. The distribution of water in the Martian atmosphere matches a profile of consta nt, 100% saturation from 10 to 45 km altitude.