ESA Science & Technology - OMEGA Spectra of Different Regions in Mars's Southern Seasonal Cap

Reflectance spectra of representative regions within Mars's southern seasonal cap. The regions a-d are those identified in the OMEGA continuum image of the southern seasonal cap (see related images). Spectra are corrected for aerosol contributions and atmospheric absorption.

CO₂ ice absorption bands are much deeper in region b (mean path length 10 cm) than in region a (mean path length 10 mm), hence region b is covered by much coarser CO₂ ice than region a.

Strong water ice absorptions dominate the reflectance spectrum of region c. The weak CO₂ absorption bands in spectra from the cryptic region (black curve, region d) cannot correspond to a surface covered by a slab of nearly pure CO₂ ice, such as that observed by OMEGA in mid-winter (green spectrum, provided for reference).

Image reproduced from the publication by Y. Langevin et al "No signature of clear CO₂ ice from the cryptic regions in Mars' south seasonal polar cap", Nature 442, 7104, pp 790-792, 2006