Search for Carbonates on Mars with the OMEGA/Mars Express Data

Introduction: Key minerals for the study of the past of Mars, such as phyllosilicates, sulfates or hydroxides, have been discovered by the Mars Express / OMEGA experiment [e.g. 1,2]. This abstract focuses on the search for carbonates from the OMEGA dataset. The presence or the lack of carbonates on the Martian surface is very important to 1) better understand the climatic and geological past of the planet, since carbonates easily form in aqueous media; 2) get new elements about the evolution of a primitive thicker CO2 atmosphere, since dissolved carbon dioxide precipitates in carbonate minerals. Moreover the carbonate formation is also largely favored by biological processes. Several Martian missions have tried unsuccessfully to detect carbonate minerals on the surface of Mars, either orbital instruments like IRS [3] or TES [4], or landers and rovers up to now. TES detected what can be interpreted as carbonates in the Martian dust but only in small amounts [5]. SNC meteorites, assumed to originate from the Martian surface, present carbonate inclusions [e.g. 6]. Several scenarios have been proposed to explain this lack of carbonate in the Martian observations, from the chemical conditions to inhibit carbonate formation [7] to their UV photolysis if they were ever formed [8]. The OMEGA investigation, on board the ESA Mars Express mission, has been mapping Mars surface by means of visible-infrared hyperspectral reflectance imagery at a 0.3to 5-kilometer resolution since December 2003. In the near-infrared all kinds of carbonate minerals exhibit two strong absorption bands at 3.4 and 3.9 μm. This abstract presents the detection method based on these bands and its results.