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Repartition of H2O and CO2 ices on the south polar cap of Mars Observations OMEGA/Mars Express

1er mars 2004

The observations of Mars Express around Mars began on 8 january, and a first publication, on which several astronomers from Paris Observatory are co-authors, is getting out in Nature about the observations by the imaging spectrometer OMEGA of polar ices on Mars. For the first time, OMEGA allows to determine directly the repartition of the two types of ices H2O and CO2.

The composition in carbon dioxide ice (CO2) or water ice (H2O) remained discussed until very recently. The observations by Mars Odyssey had shown, by indirect arguments, the presence of water ice in the southern polar cap (that was believed before made up exclusively of carbon dioxide ice). The measurements by OMEGA allow the first direct detections of the distribution of the two types of ice ; the Martian season of southern hemisphere being the end of summer, this detection shows that these ices are present permanently. The abundance of water vapor in the atmosphere being very weak on Mars, the detection of permanent reservoirs of ice is a major element to understand the ice/atmosphere exchanges during Martian seasons.

Figure 1 Cartes des glaces de CO2 et H2O au pôle sud de Mars, produites par le spectro-imageur infrarouge OMEGA de Mars Express (données du 18 janvier au 11 février 2004). A gauche, la signature d’absorption de la neige carbonique est codée du bleu (absorption forte) au marron (régions libres de glace de CO2) ; à droite, la signature spectrale de la glace d’eau est codée de même du bleu (absorption forte) au rouge (sans glace). La comparaison des deux cartes montre que l’extension de la glace d’eau est plus importante que celle de la glace de dioxyde de carbone, certaines régions étant composées de glace d’eau uniquement.
  • The OMEGA team : M. Berthé1, J-P. Bibring1, Y. Langevin1, S. Erard1, O. Forni1, A. Gendrin1, B. Gondet1, N. Manaud1, F. Poulet1, G. Poulleau1, A. Soufflot1, M. Combes2, P. Drossart2, T. Encrenaz2, T. Fouchet2, R. Melchiorri2, G. Bellucci3, F. Altieri3, V. Formisano3, G. Bonello3, S. Fonti3, F. Capaccioni3, P. Cerroni3, A. Coradini3, V. Kottsov4, N. Ignatiev4, V. Moroz4, D. Titov4, L. Zasova4, N. Mangold5, P. Pinet6, B. Schmitt7, C. Sotin8, E. Hauber9, H. Hoffmann9, R. Jaumann9, U. Keller10, R. Arvidson11, J. Mustard12, T. Duxbury13, F. Forget14
  • IAS, 91405, Orsay Campus, France, 2LESIA, Observatoire de Paris/Meudon, 92195 Meudon, 3IFSI-INAF, Rome, Italy, 4IKI, Moscow, Russia, Â 5OrsayTerre, Orsay Campus, 91405 France, 6Observatoire Midi-Pyrénées, 31000 Toulouse, France, 7Laboratoire de Planétologie, 38400 France, 8Planétologie, Université de Nantes, France, 9DLR, Berlin, Germany, 10MPAE, Lindau, Germany, 11Earth & Planeraty Sciences, Washington University, Saint-Louis, MO 63130, USA, 12Geological Sciences, Brown University, Providence, RI 02912, USA, 13JPL, Pasadena, Ca, USA, 14LMD, Université de Paris 6, 75252, Paris, France

Contact

  • Pierre Drossart (Observatoire de Paris, LESIA)
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