Details of Snowfall on Mars Explained

Clouds scoot across the Martian sky in a movie clip consisting of 10 frames taken by the Surface Stereo Imager on NASA's Phoenix Mars Lander. This clip accelerates the motion. The camera took these 10 frames over a 10-minute period. Particles of water-ice make up these clouds, like ice-crystal cirrus clouds on Earth. (Image credit: NASA/JPL- Caltech/University of Arizona/Texas A&M University)

The planetMars conjures images of red rocks and arid, dusty plains, but as NASA's PhoenixMars Lander showed last year, it snows on Mars.

Thestationary robot observed icecrystals falling to the martian surface near the end of its 5-month missionin the arctic Vastitas Borealis plains last year. Today, scientists detail thisfinding and others in a set of four papers in the journal Science. Theresearch could help shed light on the past and present action of water on themartian surface and characterize the potential habitability of the red planet.

Spacecraftorbiting Mars had previously detected clouds high up in the Martian atmosphereand low-level "ice fog," "but they've never seen precipitation,"said James Whiteway of York University in Canada, the lead scientist for Phoenix's meteorological instruments.

The cloudswere low-level, wispy clouds made up of ice crystals, similar to the cirrusclouds that form over the Earth's polar regions in the winter. Whiteway alsolikened them to the thin clouds jet planes fly through high in the Earth'satmosphere.

"Thethin, wispy clouds up there have a similar water content," he told SPACE.com.

The cloudsdidn't begin forming until around sol (Martian day) 80 or 90 of the mission,when air temperatures were cool enough for water vapor in the atmosphere tocondense out, Whiteway explained.

The snowdidn't come until close to the end of the mission. It too is similar to thesnow that falls to the ground at Earth'spoles, sometimes called "diamond dust." Whiteway describes it as"ice crystals sparkling in the air."

The snowwasn't enough to build a snowmartian with, however, amounting to only a couplemicrometers (there are 1,000 micrometers in a millimeter) a day if it wasmelted on the surface, Whiteway said.

Theobservations show that "precipitation is a component of the hydrologiccycle" on Mars, which was not suspected before the Phoenix mission,Whiteway said.

The newinformation can be used to modify Martian climate models, which currently don'tfeature these newly discovered clouds and precipitation, "and then we'llsee what the implications are," Whiteway said.

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Andrea Thompson is an associate editor at Scientific American, where she covers sustainability, energy and the environment. Prior to that, she was a senior writer covering climate science at Climate Central and a reporter and editor at Live Science, where she primarily covered Earth science and the environment. She holds a graduate degree in science health and environmental reporting from New York University, as well as a bachelor of science and and masters of science in atmospheric chemistry from the Georgia Institute of Technology.