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March
3, 2008: A NASA spacecraft in orbit around Mars has
taken the first ever image of active avalanches near the Red
Planet's north pole.
"It really surprised me," says planetary scientist
Ingrid Daubar Spitale of the University of Arizona who first
noticed the avalanches in photos taken by the Mars Reconnaissance
Orbiter on Feb. 19th. "It's great to see something so
dynamic on Mars. A lot of what we see there hasn't changed
for millions of years."
Above:
Amazingly, the full-sized
version of this HiRISE image shows not just one but four
Martian avalanches in action. [More]
The
orbiter's HiRISE (High Resolution Imaging Experiment) camera
wasn't looking for avalanches. "We were checking for
springtime changes in the carbon-dioxide frost covering a
northern dune field, and finding the avalanches was completely
serendipitous," says JPL's Candice Hansen, deputy principal
investigator for HiRISE.
The
full image reveals features as small as a desk in a strip
of terrain 6 kilometers (3.7 miles) wide and more than 10
times that long, at 84 degrees north latitude. Reddish layers
known to be rich in water ice make up the face of a steep
slope more than 700 meters (2,300 feet) tall, running the
length of the image.
"We
don't know what set off these landslides," says Patrick
Russell of the University of Berne, Switzerland, a HiRISE
team collaborator. "We plan to take more images of the
site through the changing Martian seasons to see if this kind
of avalanche happens all year or is restricted to early spring."
Material
that fell from the upper portion of the scarp is probably
more ice than dust. Imaging of the site in the months ahead
may reveal changes in the new deposit at the base of the slope.
That will help researchers estimate what proportion is ice.
"If
blocks of ice broke loose and fell, we expect the water in
them will be changing from solid to gas," Russell says.
"We'll be watching to see if blocks and other debris
shrink in size. What we learn could give us a better understanding
of one part of the water cycle on Mars."
The
avalanche photo is one of approximately 2,400 HiRISE images
released on March 3, 2008. Click
here to browse the full collection.
Another
notable HiRISE image shows a blue crescent Earth and its moon,
as seen by the Mars Reconnaissance Orbiter. The west coast
of South America is visible in the photo. Still other images
allow viewers to explore a wide variety of Martian terrains,
such as dramatic canyons and rhythmic patterns of sand dunes.
Right:
Looking back at Earth, the HiRISE camera snapped this picture
in October 2007. The complete
image shows the Moon as well. [More]
The
camera is one of six science instruments on the orbiter. The
spacecraft reached Mars in March 2006 and has returned more
data than all other current and past missions to Mars combined.
"Our
Mars program is the envy of the world," says Alan Stern,
associate administrator of NASA's Science Mission Directorate,
Washington. "We plan to launch a total of five more missions
in the next decade, beginning with the Mars Science Lab rover
next year and a Mars Aeronomy Scout mission in 2013."
Stay
tuned!
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Editor: Dr.
Tony Phillips | Credit: Science@NASA
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