NASA's Orbiter Data Confirms CO2 Snowfall on Mars

NASA's Mars Reconnaissance Orbiter (MRO) has given more clear evidence suggesting the presence of carbon dioxide snowfall on Mars.

Scientists analyzed the data collected by the Mars Climate Sounder on MRO by examining the particles present in Red planet's atmosphere in the south polar region during southern Mars winter in 2006-2007. The data gave information about temperatures, the size of the particles and their concentrations.

Based on this, scientists found a carbon-dioxide cloud which was about 300 miles (500 kilometers) and located on Mars. The data also showed evidence of carbon dioxide ice clouds falling to the surface at latitudes from 70 to 80 degrees south, reported NASA. 

While earlier studies have showed that carbon dioxide snowfall is falling on the Mars surface, the new report gives more definitive evidence of the snowfall. When the experts pointed the instrument to the horizon, they found that the clouds were tall enough and the carbon dioxide particles extended to the surface of Mars.

"These are the first definitive detections of carbon-dioxide snow clouds," lead author of the report, Paul Hayne of NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in  a statement from NASA.

"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," he said.

So far, Mars is the only planet in the solar system known to experience the CO2 snowfall. Such snowfalls require about minus 193 degrees Fahrenheit (minus 125 Celsius) temperature for the CO2 to be in frozen state, which means that the dry ice (frozen CO2 is known as dry ice) needs cooler temperatures than required to freeze water.

The dry ice is deposited in the residual ice caps in the south polar region. Mars has two types of ice caps - seasonal ice caps and residual ice caps. While the northern residual ice cap holds water ice, the southern residual ice cap is made up of dry ice. Residual ice caps remain for the entire year.  Hence, the south polar region is the one place where dry ice can remain frozen year-round.

It has been unclear as to how these CO2 from the Mars' atmosphere gets deposited as dry ice on the surface of the southern residual cap. However, the new results show evidence of snowfall falling right on the residual cap.