This is unexpected because Mars has a much thinner atmosphere thanEarth, is only about one percent as dense, and its high-speed windsare less frequent and weaker than Earth's. For years, researchers debated whether sand dunes observed on Marswere mostly fossil features related to past climate, rather thancurrently active. In the past two years, researchers using imagesfrom Mars Reconnaissance Orbiter's High Resolution Imaging ScienceExperiment (HiRISE) camera have detected and reported sandmovement. Now, scientists using HiRISE images have determined that entiredunes as thick as 200 feet (61 meters) are moving as coherent unitsacross the Martian landscape. The study was published online May 9by the journal Nature. |
"This exciting discovery will inform scientists trying tobetter understand the changing surface conditions of Mars on a moreglobal scale," said Doug McCuistion, director, NASA's MarsExploration Program, Washington. "This improved understandingof surface dynamics will provide vital information in planningfuture robotic and human Mars exploration missions." Researchers analyzed before-and-after images using a new softwaretool developed at the California Institute of Technology (Caltech)in Pasadena, Calif. The tool measured changes in the position ofsand ripples, revealing the ripples move faster the higher up theyare on a dune. The study examined images taken in 2007 and 2010 of the Nili Paterasand dune field located near the Martian equator. By correlatingthe ripples' movement to their position on the dune, the analysisdetermined the entire dunes are moving.
This allows researchers toestimate the volume, or flux, of moving sand. "We chose Nili Patera because we knew there was sand motiongoing on there, and we could quantify it," said NathanBridges, a planetary scientist at Johns Hopkins University AppliedPhysics Laboratory in Laurel, Md., and lead author of the Naturepaper. "The Nili dunes also are similar to dunes in placeslike Antarctica and to other locations on Mars." The study adds important information about the pace at whichblowing sand could be actively eroding rocks on Mars. Using the newinformation about the volume of sand that is moving, scientistsestimate rocks in Nili Patera would be worn away at about the samepace as rocks near sand dunes in Antarctica, where similar sandfluxes occur. "Our new data shows wind activity is indeed a major agent ofevolution of the landscape on Mars," said Jean-PhilippeAvouac, Caltech team leader.
"This is important because ittells us something about the current state of Mars and how theplanet is working today, geologically." Scientists calculate that if someone stood in the Nili Patera dunesand measured out a one-yard (one-meter) width, they would see morethan two cubic yards (1,500 liters) of sand pass by in an Earthyear, about as much as in a child's sand box. "No one had estimates of this flux before," said Bridges."We had seen with HiRISE that there was dune motion, but itwas an open question how much sand could be moving. Now, we cananswer that." Scientists will use the information to understand broader mysterieson Mars, like why so much of the surface appears heavily eroded,how that occurred, and whether it is a current process or it wasdone in the past. Scientists can now point to sand flux as amechanism capable of creating significant erosion today on the RedPlanet. The HiRISE camera provides unprecedented resolution in studying theMartian landscape.
NASA's Jet Propulsion Laboratory, Pasadena,Calif., a division of Caltech, manages the Mars ReconnaissanceOrbiter for NASA's Science Mission Directorate in Washington.Lockheed Martin Space Systems, Denver, built the spacecraft. HiRISEis operated by the University of Arizona and was built by BallAerospace & Technologies Corp., Boulder, Colo. For related images and more information about Mars ReconnaissanceOrbiter, visit: www.nasa.gov/mro .
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