HIGH-RESOLUTION SPECTROSCOPY OF MARS AT 3.7 AND 8 MU-M - A SENSITIVE SEARCH FOR H2O2, H2CO, HCL, AND CH4, AND DETECTION OF HDO

We report the first sensitive upper limits for H2O2, H2CO, and HCl, a sensitive upper limit for CH4, and a measured column abundance for HDO . A combination of the Kitt Peak National Observatory (KPNO) 4-m teles cope and Fourier transform spectrometer with the Goddard Space Flight Center (GSFC) postdisperser was used to observe low-latitude regions o f Mars in spectral ranges of 2650-2800 cm(-1) and 1229-1237 cm(-1) wit h resolving power nu/delta nu = 2.7 x 10(5) and 1.2 x 10(5), respectiv ely. The main spectral features are lines of isotopic CO2 and HDO. A r adiation transfer code has been developed which divides the atmosphere into 30 layers and the Voigt profile of each line in each layer into 60 intervals. This code couples the reflected solar and thermal radiat ions. A search for H2O2 at 1229-1237 cm(-1) results in a 2-sigma upper limit of 30 ppb, close to the predictions of recent photochemical mod els. Our 2-sigma upper limit for HCl (< 2 ppb) precludes any significa nt chlorine chemistry in the atmosphere. Our value for methane (70 +/- 50 ppb) is consistent with, but does not improve upon, earlier result s from Mariner 9 infrared interferometer spectrometer (IRIS). Our 2-si gma upper limit for H2CO (3 ppb) is much smaller than recently claimed abundances. The observed HDO lines result in an abundance of (6.06 +/ - 0.5) x 10(16) cm(-2), which, when compared with that of H2O measured by the Viking orbiters at the same season and latitudes, yields an en richment in the D/H ratio of a factor of 5.5 +/- 2 relative to Earth. The given uncertainty is mainly caused by possible variations of Mars' atmospheric water abundance.