Time-of-day variations of atmospheric temperature and water ice opacity observed by Mars Climate Sounder

The Mars Climate Sounder (MCS) is a mid- and far-infrared thermal emission radiometer on board the Mars Reconnaissance Orbiter (MRO). From the measured radiances, vertical profiles of atmospheric temperature, dust and water ice opacity are retrieved up to altitudes of about 80 km. Although MRO is in a sun-synchronous orbit around Mars, MCS performed off-track observations between June and Nov. 2008 (Ls=75-160) to sample the atmosphere at different local times above the Phoenix landing site. We present analyses of these measurements. The diurnal variations in the temperature profiles are characterized by a strong component due to the diurnal tide, which exhibits its clearest signature in northern mid-summer, although in some regions a semi-diurnal or higher order signal is dominant. Water ice cloud formation is strongly correlated with these tidal features. In Sep./Oct. 2010 (Ls~155) MCS is performing additional off-track measurements in support of the preparation for the entry, descent, and landing of the Mars Science Laboratory. We will present a first analysis of these time-of-day measurements and compare them with the results from the Phoenix campaigns.