NASA's Mars data indicates 'Dry Ice' snowfall

This reveals the only known example of carbon-dioxide snow falling anywhere in our solar system, NASA said in a statement.

Frozen carbon dioxide, known as "dry ice," requires temperatures of about minus 193 degrees Fahrenheit (minus 125 Celsius), which is much colder than needed for freezing water.

"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, California.

Carbon-dioxide snow reminds scientists that although some parts of Mars may look quite Earth-like, the Red Planet is very different.

"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 said.

NASA described that as the only known example of carbon-dioxide snow falling in our solar system. The snowfalls occurred from clouds around the Red Planet's south pole in winter.

"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," co-author David Kass of JPL said.

Just how the carbon dioxide from Mars' atmosphere gets deposited has been in question, NASA said.

The report is being published in the Journal of Geophysical Research.