Monitoring Atmospheric Dust Spring Activity at High Southern Latitudes on Mars using OMEGA

This article presents a monitoring of the atmospheric dust in the south polar region during spring of martian year 27. Our goal is to contribute to identify-ing the regions where the dust concentration in the atmosphere shows specific temporal patterns, for instance high, variable, and on the rise due to lifting or transport mechanisms. This identification is performed in relation with the sea-sonal ice regression. Based on a phenomenological examination of the previous results, hypothesis regarding the origin of aerosol activity of the southern polar region are proposed. This is of paramount importance since local dust storms generated in this region sometimes grow to global proportions. The imaging spectrometer OMEGA on board Mars Express has acquired the most compre-hensive set of observations to date in the near-infrared (0.93-5.1 microns) of the southern high latitudes of Mars from mid-winter solstice (Ls=110°, December 2004) to the end of the recession at Ls=320 ° (November 2005). We use two com-plementary methods in order to retrieve the optical depth of the atmospheric dust at a reference wavelength of one micron. The methods are independently operated for pixels showing mineral surfaces on the one hand and the seasonal cap on the other hand. They are applied on a time series of OMEGA images acquired between LS=220 ° and LS=280 °. As a result the aerosol optical depth (AOD) is mapped and binned at a spatial resolution of 1.0°.pixel-1 and with a mean period of AOD sampling ranging from less than two sols for latitudes higher than 80°S to approximately six sols at latitudes in the interval 65-75°S