Sand dunes in Northern Mars actively changing

Friday, February 4, 2011

WASHINGTON - An investigation led by a Planetary Science Institute researcher has revealed that the avalanche faces of huge Martian sand dunes, long thought to be frozen in time on the distant planet, are being re-sculpted on a seasonal basis.

Candice Hansen, a senior scientist at PSI and lead author of a paper, said that the vast northern dunes on Mars - covering an area larger than Texas at 845,000 square kilometers - were believed by planetary scientists to be fairly static, shaped long ago when winds on the planet’s surface were much stronger than seen today.

New images from the High Resolution Imaging Science Experiment (HiRISE) camera aboard NASA’s Mars Reconnaissance Orbiter tell a different story.

“Many dunes in the northern polar region of Mars have shown substantial changes in morphology within just one Martian year,” said Hansen, who also serves as deputy principal investigator on the HiRISE team.

A seasonal layer of frozen carbon dioxide, or dry ice, that blankets the region in winter and sublimates, or changes from solid to gasstate, in the spring is responsible for the annual erosion of the polar Martian dunes, Hansen said.

“This gas flow destabilizes the sand, causing avalanches and creating new alcoves, gullies and sand aprons on Martian dunes,” she said.

Comparing images from the HiRISE camera taken over two Mars years-about four Earth years-the team led by Hansen discovered that the dunes they studied at high latitudes showed changes indicating that they are not strongly crusted or ice cemented, as previously assumed by Mars scientists.

“The level of erosion in just one Mars year was really astonishing,” Hansen said. “In some places hundreds of cubic yards of sand have avalanched down the face of the dunes.”

The study appears in the journal Science. (ANI)

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