Mapping of Mars O2 1.27 μm dayglow at four seasonal points

The O2 dayglow at 1.27 μm is formed by high-altitude ozone on Mars and is a sensitive tracer of Mars photochemistry. Mapping of this dayglow using the IRTF/CSHELL long-slit spectrograph requires the extraction of weak emission lines against a strong continuum of the reflected solar light. Some new tools are suggested to improve the data processing. The observed O2 dayglow intensities at LS=67°, 112°, 148°, and 173° show a decrease from late spring (aphelion) to fall equinox by a factor of ≈5 at low latitudes (±30°). This decrease agrees with that predicted by a model of Clancy and Nair (1996, J. Geophys. Res. 101 (12) 12785–12790), although the dayglow intensities are weaker than those based on that model. The measured dayglow variations with latitude are rather low at LS=67°, 112°, and 148° and unexpectedly high at 173°. The dayglow intensity peaks near noon and is smaller at 9:00 and 16:30 LT by a factor of 2. Some data on the ozone profile near aphelion are obtained from a combination of the dayglow and ozone observations. It is hardly possible to detect the O2 night airglow at 1.27 μm on Mars using the existing ground-based and on-orbit instruments. The O2 dayglow intensity as a function of latitude and season from aphelion to fall equinox has been obtained. Our goal is to extend this distribution to the full martian year and get a database for Mars photochemistry to complement the MGS/TES observations of water vapor, atmospheric temperature, and dust and ice aerosol.