Observations of the south seasonal cap of Mars during recession in 2004–2006 by the OMEGA visible/near‐infrared imaging spectrometer on board Mars Express

Abstract

[1] The OMEGA visible/near-infrared imaging spectrometer on board Mars Express has observed the southern seasonal cap in late 2004 and 2005 and then in the summer of 2006. These observations extended from the period of maximum extension, close to the southern winter solstice, to the end of the recession at L s 325°. The spectral range and spectral resolution of OMEGA make it possible to monitor the extent and effective grain size of CO 2 ice and H 2 O ice on the ground, the level of contamination of CO 2 ice and H 2 O ice by dust, and the column density of mm-sized ice grains in the atmosphere. The CO 2 seasonal cap is very clean and clear in early southern winter. Contamination by H 2 O ice spreads eastward from the Hellas basin until the southern spring equinox. During southern spring and summer, there is a very complex evolution in terms of effective grain size of CO 2 ice and contamination by dust or H 2 O ice. H 2 O ice does not play a significant role close to the southern summer solstice. Contamination of CO 2 ice by H 2 O ice is only observed close to the end of the recession, as well as the few H 2 O ice patches already reported by Bibring et al. (2004a). These observations have been compared to the results of a general circulation model, with good qualitative agreement on the distribution of H 2 O ice on the surface and in the atmosphere. Resolving the remaining discrepancies will improve our understanding of the water cycle on Mars.

HiRISE observations of gas sublimation-driven activity in Mars’ southern polar regions: II. Surficial deposits and their origins

“…19, we show the 1.434 lm/1.245 lm ratios of the I/F values within the two cubes. A wavelength of 1.434 lm is within a major CO 2 absorption feature and at the wavelength used by Langevin et al (2007) (within one pixel in wavelength) for the interpretation of OMEGA data. On the right, the image is bright and bland with few noticeable features.…”

The present and past climates of planet Mars

“…If this scenario is confirmed, the presence of thick deposits composed of hundreds of alternatively dark and bright layers in the polar regions can probably be attributed to the past oscillations of the climate [35,41]. Fig.…”

“…In the southern hemisphere, the cap recession is asymmetric and strongly varies with longitude [33,35]. Furthermore, a small residual cap made of "perennial" carbonic ice survives each year through the summer.…”

Exploration of Planetary Hyperspectral Images with Unsupervised Spectral Unmixing: A Case Study of Planet Mars

“…In particular, classical analyses by spectral index methods have been carried out for determining the spatio-temporal distribution of H 2 O and CO 2 ices at the high latitudes of the red planet [12,14,15]. More generally, these rather simple methods require prior knowledge of the compounds expected on the scene and on their characteristic spectral signatures, such as the position and shape of the distinctive absorption bands.…”

“…The OMEGA instrument provides a global coverage at a medium resolution (1-4 km) of the entire surface of Mars, as well as snapshots of selected areas with a resolution of a few hundreds of meters. OMEGA has provided a wealth of information concerning the composition and distribution of minerals and volatile species at the surface and in the atmosphere of Mars through the spectral analysis of the re-diffused solar light [10][11][12][13].…”