Indication for H2O in the upper atmosphere of Mars

Ground-based observations of non-LTE emission lines of Martian CO₂ have been made with adequate spatial and spectral resolution to investigate processes at altitudes between 50 and 90 km above the surface. Measurements of the band integrated steradiancy at various locations on the planetary disc during the opposition 1982 show an increase of the emission over the north polar cap, which cannot be explained by standard models assuming a pure CO₂ atmosphere. The results indicate both a substantial influence of H₂O on the emission process, and a somewhat supersaturated H₂O vapour in the emitting atmospheric layer.