NASA researchers announced last week that data from the Mars Reconnaissance Orbiter has given the “clearest evidence yet” of dry ice snowfalls on Mars. Dry ice, as it is commonly known, is frozen carbon dioxide.

“These are the first definitive detections of carbon-dioxide snow clouds,” said Paul Hayne of NASA’s Jet Propulsion Laboratory. “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.”

Hayne is the lead author of the study which lays out the evidence for the Martian snowfall. The study will be published in the Journal of Geophysical Research.

It was announced back in June that scientists had been able to determine the presence of carbon dioxide clouds. Now it seems clear that there is actually some carbon dioxide snowfall on the red planet.

According to NASA, the snowfall occurred around Mars’ south pole during its winter. The data analyzed by researchers comes from the Mars Reconnaissance Orbiter and the Mars Climate Sounder, taken in the Mars winter of 2006-2007. The south pole of Mars is the only place on the planet that dry ice stays on the surface year-round.

“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,” said study co-author David Kass of JPL. “Another comes from observations when the instrument is pointed toward the horizon, instead of down at the surface. The infrared spectra signature of the clouds viewed from this angle is clearly carbon-dioxide ice particles and they extend to the surface. By observing this way, the Mars Climate Sounder is able to distinguish the particles in the atmosphere from the dry ice on the surface.”

(Image Courtesy NASA/JPL-Caltech)