This paper reports the first detections of two high-altitude nighttime CO2 clouds on Mars during southern summer (Ls=264° and Ls=330°) with stellar occultation measurements by the Imaging Ultraviolet Spectrograph on board the Mars Atmosphere and Volatile Evolution spacecraft. Interpretation of the transmission spectra with Mie theory indicates particle radii of ∼90–110 nm assuming a monodisperse distribution. The altitude profile of extinction indicates that the cloud layers are confined horizontally to sizes less than ∼500–700 km. Examination of the CO2 density and temperature profiles reveals strong wave-like perturbations. Supersaturated temperatures occur at the maximum negative extent of these wave-like perturbations, which are organized in longitude with a dominant m=3 zonal harmonic. This suggests that tides are important in the formation of CO2 clouds.
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)