Pasadena, CA (NASA) - NASA's Mars Reconnaissance Orbiter data has given scientists the clearest evidence yet of carbon-dioxide snowfalls on Mars.
This reveals the only known example of carbon-dioxide snow falling anywhere in our solar system.
"These are the first definitive detections of carbon-dioxide snow clouds," said the report's lead author, Paul Hayne of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We firmly establish the clouds are composed of carbon dioxide -- flakes of Martian air -- and they are thick enough to result in snowfall accumulation at the surface."
The snowfalls occurred from clouds around the Red Planet's south pole in winter. The presence of carbon-dioxide ice in Mars' seasonal and residual southern polar caps has been known for decades. Also, NASA's Phoenix Lander mission in 2008 observed falling water-ice snow on northern Mars.
Mars' south polar residual ice cap is the only place on the Red Planet where frozen carbon dioxide persists on the surface year-round. Just how the carbon dioxide from Mars' atmosphere gets deposited has been in question. It is unclear whether it occurs as snow or by freezing out at ground level as frost. These results show snowfall is especially vigorous on top of the residual cap.
"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," Hayne said.
JPL, a division of the California Institute of Technology in Pasadena, provided the Mars Climate Sounder instrument and manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate in Washington.