Scientists have discovered carbon-dioxide snow clouds on Mars, the first such phenomenon of its kind to be detected. NASA's Mars Reconnaissance Orbiter (MRO), which "measures nine different wavelengths of visible and infrared light," provided data from the Red Planet's 2006-2007 South Pole winter. At its north pole, Mars also shows a sign of water-ice snow, which naturally occurs on earth. Water-ice snow was originally discovered by NASA's Phoenix lander in 2008.
NASA's Paul Hayne notes, "We firmly establish the clouds are composed of carbon dioxide-flakes of Maritain air-and they are thick enough to result in snowfall accumulation at the surface."
The MRO showed that "The infrared spectra signature of the clouds viewed from this angle is clearly carbon-dioxide ice particles, and they extend to the surface," said NASA's David Kass. "By observing this way, the Mars Climate Sounder is able to distinguish the particles in the atmosphere from the dry ice on the surface."
Kass adds, "One line of evidence for snow is that the carbon-dioxide ice particles in the clouds are large enough to fall to the ground during the lifespan of the clouds. Another comes from observations when the instrument is pointed toward the horizon, instead of down at the surface."
Hayne touched on the implications of carbon dioxide snow clouds, clarifying that "the finding of snowfall could mean that the type of deposition-snow or frost-is somehow linked to the year-to-year preservation of the residual cap."
The Christian Science Monitor states that NASA's study will be published in a future issue of the Journal of Geophysical Research.
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