On Mars, Dry Ice 'Smoke' Carves Up Sand Dunes

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NASA's Mars Reconnaissance Orbiter snapped this series of pictures of sand dunes in the north polar region of Mars, showing how dark sand rises to the top as spring progresses (from left to right) and a surface layer of carbon dioxide ice crack.
NASA/JPL-Caltech/Univ. of Arizona

The seasonal thawing of carbon dioxide ice near Mars' north pole carves grooves in the region's sand dunes, three new studies reveal.

The discovery, made using observations from NASA's Mars Reconnaissance Orbiter spacecraft (MRO), reinforces that the Red Planet's surface continues to be transformed today, even though Mars' volcanoes have died out and its liquid surface water apparently dried up long ago.

"It's an amazingly dynamic process," Candice Hansen of the Planetary Science Institute in Tucson, Ariz., lead author of one of the studies, said in a statement. "We had this old paradigm that all the action on Mars was billions of years ago. Thanks to the ability to monitor changes with the Mars Reconnaissance Orbiter, one of the new paradigms is that Mars has many active processes today."

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MRO photographed dunes in Mars' far northern latitudes using its High Resolution Imaging Science Experiment camera, or HiRise. The images revealed a number of grooves appearing in the dunes as the northern spring took hold and progressed. (Dry Ice 'Smoke' Moves Mars Sand (Video))

The phenomenon is driven by the springtime thawing of a surface layer of frozen carbon dioxide, also known as dry ice.

This thawing occurs first on the ice layer's underside, which is in contact with the warming ground, researchers said. The dry ice sublimes from a solid state to a gaseous one, and pressure builds as more and more gas is produced and trapped.

Eventually, cracks form in the ice and some of the carbon dioxide gas breaks free, forming temporary grooves in the dune as it hisses out.