Fast-traveling martian sand dunes takes everyone by surprise
Thu, 10/05/2012 - 16:47 by RESHMI CHAKRAVORTY
New images from NASA of shifting sand dunes on Mars prove that they are speedier than once thought. The new data contradict beliefs that the surface of Mars was static and unchanging.
NASA's Mars Reconnaissance Orbiter has revealed that movement in sand dune fields on the Red Planet occurs on a surprisingly large scale, about the same as in dune fields on Earth.
This is unexpected because Mars has an atmosphere 100 times less dense than Earth's, and its high-speed winds are less frequent and weaker 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.
For years, researchers debated whether sand dunes observed on Mars were mostly fossil features related to past climate, rather than whether they are currently active or not. In the past two years, researchers using images from Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE) camera have detected and reported sand movement. Now, scientists using HiRISE images have determined that entire dunes as thick as 200 feet (61 meters) are moving as coherent units across the Martian landscape.
This exciting discovery will further encourage scientists, who are trying their best to understand the changing surface conditions of Mars on a more global scale better," said Doug McCuistion, director, NASA's Mars Exploration Program, Washington. "This improved understanding of surface dynamics will provide vital information in planning future robotic and human Mars exploration missions."
"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.
The research appeared in this week's journal Nature.