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Marks on Martian Dunes May Be Tracks of Dry-Ice Sleds

NASA research indicates hunks of frozen carbon dioxide -- dry ice -- may glide down some Martian sand dunes on cushions of gas similar to miniature hovercraft, plowing furrows as they go.
Researchers deduced this process could explain one enigmatic class of gullies seen on Martian sand dunes by examining images from NASA's Mars Reconnaissance Orbiter (MRO) and performing experiments on sand dunes in Utah and California.

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Thawing 'Dry Ice' Drives Groovy Action on Mars

Researchers using NASA's Mars Reconnaissance Orbiter see seasonal changes on far-northern Martian sand dunes caused by warming of a winter blanket of frozen carbon dioxide.
A driving factor in the springtime changes where seasonal coverings of dry ice form on Mars is that thawing occurs at the underside of the ice sheet, where it is in contact with dark ground being warmed by early-spring sunshine through translucent ice. The trapped gas builds up pressure and breaks out in various ways.
Transient grooves form on dunes when gas trapped under the ice blanket finds an escape point and whooshes out, carrying out sand with it. The expelled sand forms dark fans or streaks on top of the ice layer at first, but this evidence disappears with the seasonal ice, and summer winds erase most of the grooves in the dunes before the next winter. The grooves are smaller features than the gullies that earlier research linked to carbon-dioxide sublimation on steeper dune slopes.

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 Dunes on Mars move just like on Earth

A new study has found sand dunes on Mars are at least five times more active than earlier estimates, being comparable to dune movement rates on Earth.
The findings by researchers including Dr Nathan Bridges from the Johns Hopkins University in the United States, means a rethink of current models for past atmospheric conditions on the red planet.

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Dunes in Noachis Terra
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Dunes in Noachis Terra Region of Mars

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This enhanced-colour image shows sand dunes trapped in an impact crater in Noachis Terra, Mars. Dunes and sand ripples of various shapes and sizes display the natural beauty created by physical processes. The area covered in the image is about 1 kilometre across.
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NASA Orbiter Catches Mars Sand Dunes In Motion
 
Images from NASA's Mars Reconnaissance Orbiter (MRO) show sand dunes and ripples moving across the surface of Mars at dozens of locations and shifting up to several yards. These observations reveal the planet's sandy surface is more dynamic than previously thought.
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Northern Mars Landscape Actively Changing

Sand dunes in a vast area of northern Mars long thought to be frozen in time are changing with both sudden and gradual motions, according to research using images from a NASA orbiter.
These dune fields cover an area the size of Texas in a band around the planet at the edge of Mars' north polar cap. The new findings suggest they are among the most active landscapes on Mars. However, few changes in these dark-toned dunes had been detected before a campaign of repeated imaging by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter, which reached Mars five years ago next month.

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