'Dry Ice' Snowfall On Mars |
NASA’s Mars Reconnaissance Orbiter data have 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.
Frozen carbon dioxide, better known as “dry ice,” requires temperatures of about minus 193 degrees Fahrenheit (minus 125 Celsius), which is much colder than needed for freezing water. Carbon-dioxide snow reminds scientists that although some parts of Mars may look quite Earth-like, the Red Planet is very different. The report is being published in the Journal of Geophysical Research.
"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.
Hayne and six co-authors analyzed data gained by looking at clouds straight overhead and sideways with the Mars Climate Sounder, one of six instruments on the Mars Reconnaissance Orbiter. This instrument records brightness in nine wavebands of visible and infrared light as a way to examine particles and gases in the Martian atmosphere. The analysis was conducted while Hayne was a post-doctoral fellow at the California Institute of Technology in Pasadena. continue reading