The images, taken Feb. 19, show clouds of dust and ice billowing away from a 2,300-foot slope near the planet's north pole.
Capturing the pictures was a fortuitous accident, according to project scientist Candice Hansen, of NASA's Jet Propulsion Laboratory. The High Resolution Imaging Experiment (HiRISE) camera aboard the Mars Reconnaissance Orbiter had been doing routine imaging of seasonal changes on the planet when it caught the avalanches in progress.
"We were checking for springtime changes in the carbon-dioxide frost covering a dune field and finding the avalanches was completely serendipitous," Hansen said in a statement.
The pictures are particularly interesting because most images of Mars show static landscapes -- only a few have shown events, such as dust storms, in the process of shaping those landscapes, according to New Scientist.
Researchers had suspected that avalanches occurred on Mars, but had no photographic evidence before now.
"We saw with HiRISE more than a year ago that there were blocks sitting there at the base of the slope, so that made us think these things must be falling down, but we had no idea on what timescale," HiRISE Principal Investigator Alfred McEwen told New Scientist.
The researchers don't know what triggered the avalanches, although they speculate that it could be rising springtime temperatures melting ice, or possibly a "Mars-quake" or meteorite hit.
They plan to continue taking images of the site throughout the coming months to look for changes in the debris at the bottom of the slope.
"If blocks of ice broke loose and fell, we expect the water in them will be changing from solid to gas," HiRISE scientist Patrick Russell, of the University of Berne, Switzerland, said in a statement. "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."
