3 MARS YEARS OF DUST OPTICAL DEPTH MAPPING BY OMEGA ABOVE THE SOUTH POLE. M. Vincendon

Introduction: The varying amount of airborne dust particles observed at high latitudes directly affects the polar energy balance of Mars [1]. The behavior of aerosols above the south polar cap differs from that seen in equatorial and mid-latitude regions ([2], [3], [4]). It can however not be determined by classical thermal infrared methods of optical depth retrieval as the thermal contrast between surface ice and atmosphere is too low [5]. The strong near-IR absorptions of CO2 ice enabled the development of a new method to retrieve optical depths which requires the presence of clean CO2 ice at the surface [4]. We have extended the application of this method to 2007 and 2009 springs and summers and compared the results to the 2005 retrievals presented in [4]. This new time range includes the planet-encircling dust event of July 2007. Modeling results which aim at determining the amount of deposited dust during this global dust storm will also be presented at the conference.