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No signature of clear CO<SUB>2</SUB> ice from the cryptic regions in Mars' south seasonal polar cap

No signature of clear CO2 ice from the cryptic regions in Mars' south seasonal polar cap

Publication date: 18 August 2006

Authors: Langevin, Y. et al.

Journal: Nature
Volume: 442
Issue: 7104
Page: 790-792
Year: 2006

Copyright: Nature Publishing Group

The seasonal polar ice caps of Mars are composed mainly of CO2 ice. A region of low (< 30%) albedo has been observed within the south seasonal cap during early to mid-spring. The low temperature of this 'cryptic region' has been attributed to a clear slab of nearly pure CO2 ice, with the low albedo resulting from absorption by the underlying surface. Here we report near-infrared imaging spectroscopy of the south seasonal cap. The deep and broad CO2 absorption bands that are expected in the near-infrared with a thick transparent slab of CO2 ice are not observed. Models of the observed spectra indicate that the low albedo results from extensive dust contamination close to the surface of a CO2 ice layer, which could be linked to atmospheric circulation patterns. The strength of the CO2 absorption increases after mid-spring, so part of the dust is either carried away or buried more deeply in the ice layer during the CO2 ice sublimation process.

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