Martian Mesospheric Clouds: Latest Results from THEMIS-VIS

We present an update of THEMIS-VIS observations of clouds in the Martian mesosphere. These observations were previously discussed by McConnochie et al. [2005, Eos Trans. AGU, 86(52), Fall Meet. Suppl., Abstract P21E-03]. In addition to the ongoing THEMIS-VIS studies, recent observations of mesospheric clouds by Mars Global Surveyor [Clancy et al. 2004, Bull. Amer. Astron. Soc., 36 pg. 1128], and by SPICAM on Mars Express [Montmessin et al., 2006, Icarus 183, 403-410], are contributing to a rapid evolution in our understanding of these high-altitude aerosols. THEMIS-VIS measures cloud altitude using the parallax drift of high-altitude features, and the velocity by exploiting the time delay in the THEMIS-VIS imaging sequence. Additionally, the high resolution nadir-pointed THEMIS-VIS observations show cloud morphologies at scales on the order of 30 meters per pixel. The new results that we present include the distribution of the mesospheric clouds in location, season, altitude and velocity; comparison of the cloud velocities with GCM wind estimates; morphological classification of the clouds; and inferences about the mass, particle size, and composition of the aerosols derived from radiative transfer modeling.