[meteorite-list] MRO Detects Large Changes in Martian Sand Dunes

[Ron Baalke]

May 9, 2012

Dwayne Brown 
Headquarters, Washington      
202-358-1726 
dwayne.c.brown at nasa.gov 

Geoff Brown 
Johns Hopkins University Applied Physics Laboratory, Laurel, Md. 
240-228-5618 
geoffrey.brown at jhuapl.edu 

Guy Webster 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-6278 
guy.webster at jpl.nasa.gov 

RELEASE: 12-152

NASA MARS SPACECRAFT DETECTS LARGE CHANGES IN MARTIAN SAND DUNES

WASHINGTON -- NASA's Mars Reconnaissance Orbiter (MRO) 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 a much thinner atmosphere than 
Earth, is only about one percent as dense, and its high-speed winds 
are less frequent and weaker than Earth's. 

For years, researchers debated whether or not sand dunes observed on 
Mars were mostly fossil features related to past climate, rather than 
currently active. In the past two years, researchers using images 
from MRO'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 are moving as coherent units across the Martian 
landscape. The study was published online today by the journal 
Nature. 

"This exciting discovery will inform scientists trying to better 
understand the changing surface conditions of Mars on a more global 
scale," said Doug McCuistion, director of NASA's Mars Exploration 
Program in Washington. "This improved understanding of surface 
dynamics will provide vital information in planning future robotic 
and human Mars exploration missions." 

Researchers analyzed before-and-after images using a new software tool 
developed at the California Institute of Technology (Caltech) in 
Pasadena. The tool measured changes in the position of sand ripples, 
revealing the ripples move faster the higher up they are on a dune. 

The study examined images taken in 2007 and 2010 of the Nili Patera 
sand dune field located near the Martian equator. By correlating 
ripples' movement to their position on the dune, the analysis 
determined the entire dunes are moving. This allows researchers to 
estimate the volume, or flux, of moving sand. 

"We chose Nili Patera because we knew there was sand motion going on 
there, and we could quantify it," said Nathan Bridges, a planetary 
scientist at Johns Hopkins University Applied Physics Laboratory in 
Laurel, Md., and lead author of the Nature paper. "The Nili dunes 
also are similar to dunes in places like Antarctica and to other 
locations on Mars." 

The study adds important information about the pace at which blowing 
sand could be actively eroding rocks on Mars. Using the new 
information about the volume of sand that is moving, scientists 
estimate rocks in Nili Patera would be worn away at about the same 
pace as rocks near sand dunes in Antarctica, where similar sand 
fluxes occur. 

"Our new data shows wind activity is indeed a major agent of evolution 
of the landscape on Mars," said Jean-Philippe Avouac, Caltech team 
leader. "This is important because it tells us something about the 
current state of Mars and how the planet is working today, 
geologically." 

Scientists calculate that if someone stood in the Nili Patera dunes 
and measured out a one-yard width, they would see more than two cubic 
yards of sand pass by in an Earth year, about as much as in a 
children's sand box. 

"No one had estimates of this flux before," said Bridges. "We had seen 
with HiRISE that there was dune motion, but it was an open question 
how much sand could be moving. Now, we can answer that." 

Scientists will use the information to understand broader mysteries on 
Mars, like why so much of the surface appears heavily eroded, how 
that occurred, and whether it is a current process or it was done in 
the past. Scientists can now point to sand flux as a mechanism 
capable of creating significant erosion today on the Red Planet. 

The HiRISE camera provides unprecedented resolution in studying the 
Martian landscape. NASA's Jet Propulsion Laboratory manages MRO for 
NASA's Science Mission Directorate in Washington. Lockheed Martin 
Space Systems, Denver, built the spacecraft. HiRISE is operated by 
the University of Arizona and was built by Ball Aerospace & 
Technologies Corp., Boulder, Colo. 

For related images and more information about MRO, visit: 

http://www.nasa.gov/mro 
	
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