Detail of Mars' barchan dunes.NASA/JPL/University of Arizona
Fast-traveling sand dunes indicate the Red Planet's surface is more active than previously thought.
Because Mars has an atmosphere 100 times less dense than Earth's, scientists figured hurricane-force winds are needed to move sand around in the thin Martian air, and winds that high are rare.
But this turns out to be only half the story.
New analysis of high-resolution images, taken by NASA's Mars Reconnaissance Orbiter, show sand dunes in an area known as Nili Patera are shifting as fast as some dunes on Earth -- despite a dearth of high-speed winds.
Scientists suspect it takes a big wind to get sand particles airborne, but once launched from the surface, they bounce around with ease, thanks to the planet's thin atmosphere and low gravity.
"It's kind of like playing golf on the moon -- (the sand) goes really high and far compared to what it does on Earth. When it lands it can pick up really large speeds -- even with low wind speeds -- and splash a whole bunch of other particles to keep the process going," Jasper Kok, with the Earth and Atmospheric Sciences department at Cornell University, told Discovery News.
Once sand gets moving on Mars, wind speeds can drop by a factor of 10 and still be strong enough to transport as much sand as what moves around many places on Earth, the new study shows.
The amount of sand moving around Nili Patera, for example, could fill up a children's sandbox each year, estimates Nathan Bridges, a planetary scientist with Johns Hopkins University.
That may not sound like much, but it adds up over time. It also may explain why many landscapes on Mars are so eroded.
One prominent example can be found inside Gale Crater, the landing site for NASA's upcoming Mars Science Laboratory mission, which is scheduled to begin in August.
At the center of the crater is a three-mile-high mound of debris, believed to be the eroded remnants of sediment that once filled the basin.
"We show a mechanism where this blowing sand can actually erode rock, can erode landscapes. It can be a fairly active process in the current environment," Bridges told Discovery News.
"Up to a few years ago, it was uncertain how much the sand dunes were moving on Mars, or even if they were moving at all," Bridges added.
Analysis of additional Martian sand dunes, including some found around Gale Crater, is under way.
The research appears in this week's Nature.