Martian canyons may have been carved by wind

Martian canyons may have been carved by wind
By Emily Conover 9 March 2015 12:00 pm

Ancient canyons scar the surface of Mars, a relic from a time billions of years ago when rivers flowed on its surface. But water may not be the only factor that shaped these canyons—the wind whipping through them could be just as important, according to a new study of river canyons on Earth. Scientists studying chasms in the Andes mountains in northeast Chile have found that wind carves some canyons 10 times faster than water. The discovery may be significant for understanding how much water flowed on the surface of ancient Mars.

“The rates at which valleys and canyons can be abraded by the wind has not been well understood, and I think that is where this paper makes a great contribution,” says planetary geologist Nathan Bridges of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.

Even on Earth, it is usually difficult to disentangle the wind’s effect on a canyon from that of water. But geologist Jonathan Perkins of the University of California, Santa Cruz, and colleagues found a perfect “natural experiment” to tease out each force’s role: 36 canyons in northeast Chile, clustered into two groups. The type of rock and the climate were similar for all the canyons, but the first group was exposed to strong wind, and the second was shielded by a mountain.

When researchers compared the two sets of canyons using satellite imagery, they found that the windswept canyons were longer, smoother, and had grown 10 times faster than the still canyons over the millions of years since the rock first formed, they report online today in Nature Geoscience. The windy canyons formed long gouges in the earth reminiscent of cat scratches, whereas the calmer canyons were stubby and shaped like amphitheaters. Apparently,­ abrasion caused by windblown sand had lengthened the canyons and polished out the kinks in their slopes.

More:
http://news.sciencemag.org/earth/2015/03/martian-canyons-may-have-been-carved-wind