Caught in the act: The upper part of the slope, which is around 700-metres-tall, can be seen at the top of the image. Clouds of dust can be seen in the wake of the avalanche at the bottom (see links at foot of story for larger images).
Credit: NASA
SYDNEY: NASA's Mars Reconnaissance Orbiter has taken the first ever images of avalanches of ice and dust careening down slopes near the planet's north pole.
"It really surprised me," says planetary scientist Ingrid Daubar Spitale of the University of Arizona, in Tucson, who first noticed the avalanches in photos taken by the spacecraft on 19 February. "It's great to see something so dynamic on Mars. A lot of what we see there hasn't changed for millions of years."
The full image reveals features as small as a desk in a strip of terrain six-kilometres-wide and more than 10 times as long, at. Reddish layers known to be rich in water ice make up the face of a steep slope more than 700 m tall, running along the image. Clouds of reddish brown dust can be seen rising in the wake of the avalanche.
Serendipitous discovery
"We don't know what set off these landslides," said Patrick Russell of the University of Berne in Switzerland, who collaborates with the NASA team. "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 the proportion of ice.
"If blocks of ice broke loose and fell, we expect the water in them will be changing from solid to gas," Russell said. "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 Mars Reconnaissance Orbiter's HiRISE (High Resolution Imaging Experiment) camera, which captured the images, wasn't even looking for avalanches, said Candice Hansen, at NASA's Jet Propulsion Laboratory in California. "We were checking for springtime changes in the carbon-dioxide frost covering a northern dune field, and finding the avalanches was completely serendipitous."
with NASA
