A Nasa spacecraft has captured an avalanche of fine ice and dust thundering over a cliff near Mars's north pole.
It's not the first avalanche captured by the HiRISE camera aboard the Mars Reconnaissance Orbiter - Nasa first detected the phenomenon in 2008, believed to be caused by a thin 'crust' of frozen carbon dioxide (dry ice) which forms during the Martian winter.
Ice and dust cascade over a Martian cliff: The camera on the Mars Reconnaissance Orbiter captured the avalanche near Mars's north pole
The HiRISE high resolution camera took the amazing photograph at 85 degrees north on the planet.
The HiRISE camera is one of several hi-tech instruments on board Mars Reconnaissance Orbiter. It's the largest camera ever carried into deep space.
Nasa's ground team says that the events are detectable by a cloud of fine material that erupts when avalanches collapse down slopes on the planet.
Fine ice and dust cascades over a martian polar cliff in March 2010 in another picture captured by the Mars Reconnaissance Orbiter's HiRISE camera.