Winter and spring evolution of northern seasonal deposits on Mars from OMEGA on Mars Express

T. Appéré (1) , B. Schmitt (1) , Y. Langevin (2) , S. Douté (1) , A. Pommerol (1) , François Forget (3) , Aymeric Spiga (3) , B. Gondet (2) , J.-P. Bibring (2)

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
2 IAS - Institut d'astrophysique spatiale
3 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)

The OMEGA visible/near-infrared imaging spectrometer on Mars Express has observed the retreat of the northern seasonal deposits during Martian year 27-28 from the period of maximum extension, close to the northern winter solstice, to the end of the retreat at L s 95°. We present the temporal and spatial distributions of both CO 2 and H 2O ices and propose a scenario that describes the winter and spring evolution of the northern seasonal deposits. During winter, the CO 2-rich condensates are initially transparent and could be in slab form. A water ice annulus surrounds the sublimating CO 2 ice, extending over 6° of latitude at L s 320°, decreasing to 2° at L s 350°, and gradually increasing to 4.5° at L s 50°. This annulus first consists of thin frost as observed by the Viking Lander 2 and is then overlaid by H 2O grains trapped in the CO 2-rich ice layer and released during CO 2 sublimation. By L s 50, H 2O ice spectrally dominates most of the deposits. In order to hide the still several tens of centimeters thick CO 2 ice layer in central areas of the cap we propose the buildup of an optically thick top layer of H 2O ice from ice grains previously embedded in the CO 2 ice and by cold trapping of water vapor from the sublimating water ice annulus. The CO 2 ice signature locally reappears between L s 50 and 70. What emerges from our observations is a very active surface-atmosphere water cycle. These data provide additional constraints to the general circulation models simulating the Martian climate. Copyright 2011 by the American Geophysical Union.

Domaines: Planétologie; Glaciologie

T. Appéré, B. Schmitt, Y. Langevin, S. Douté, A. Pommerol, et al.. Winter and spring evolution of northern seasonal deposits on Mars from OMEGA on Mars Express. Journal of Geophysical Research. Planets, 2011, 116 (5), pp.E05001. ⟨10.1029/2010JE003762⟩. ⟨hal-01132273⟩