A NASA spacecraft has taken the first-ever image of an avalanche in action near Mars' north pole.
The High Resolution Imaging Experiment on NASA's Mars Reconnaissance Orbiter took the photograph Feb. 19. The image, released today, shows tan clouds billowing away from the foot of a towering slope, where ice and dust have just cascaded down.
The camera was tracking seasonal changes on Mars when it inadvertently caught the avalanche on film.
HiRISE mission scientist Ingrid Daubar Spitale of the University of Arizona was the first person to notice the avalanche when sifting through images.
"It really surprised me," she said. "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 3.7 miles (6 kilometers) 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 2,300 feet (700 meters) tall, running the length of the image.
Mars' north pole is covered by a cap of ice, and it even snows there.
The scientists suspect that more ice than dust probably makes up the material that fell from the upper portion of the scarp.
"If blocks of ice broke loose and fell, we expect the water in them will be changing from solid to gas," said Patrick Russell of the University of Berne, Switzerland, a HiRISE team collaborator. "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."
What set off the landslide and whether such events are common on Mars is something else the team will be looking at.
"We don't know what set off these landslides," Russell said. "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."