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HindustanTimes Mon,20 Oct 2014

Life and Universe

Shifting sand dunes spotted on Mars
PTI
Washington, November 28, 2011
First Published: 19:03 IST(28/11/2011)
Last Updated: 19:06 IST(28/11/2011)

For the first time, scientists have discovered shifting sand dunes and ripples all over Mars, a finding which suggests strong winds keep the sandy surface of the Red planet much more active than ever imagined.

Images captured by NASA spacecraft Mars Reconnaissance Orbiter showed that wind-blown sand dunes moving across the Martian surface, sometimes up to several yards at a time, the scientists said.

"Mars either has more gusts of wind than we knew about before, or the winds are capable of transporting more sand," lead researcher Nathan Bridges, a planetary scientist at the Applied Physics Laboratory of Johns Hopkins University in the US, said.

"We used to think of the sand on Mars as relatively immobile, so these new observations are changing our whole perspective," Bridges was quoted as saying by SPACE.com.

Scientists have long known that the red dust on Mars can swirl and blow about in many ways, ranging from vast dust storms to small whirlwinds, called dust devils. But less than 10 years ago, astronomers still thought the Martian dunes and sand ripples were either immobile or moved too minutely to ever see.

Sand dunes

According to the scientists, who detailed their findings in the journal Geology, the dark sand grains of Mars are harder to move than those of Earth's deserts and beaches because they are larger, and because the Martian atmosphere is thinner than Earth's.

Wind tunnel tests have shown that 130 kmph gusts are required on Mars to move a single a patch of sand, while on Earth, the winds about 16 kmph can achieve the same feat.

But such high wind speeds on Mars are relatively rare, according to observations from NASA's Viking landers collected in the 1970s and 1980s.

The first clues of the Red Planet's moving sand dunes came from NASA's Mars Global Surveyor. More evidence was found by NASA's Mars Exploration Rovers which detected shifting sand when they touched down on the surface of Mars in 2004.


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