This amazing photo was captured late last month by the Mars Reconnaissance Orbiter as it flew over the north pole of the red planet. It shows fine-grains and chunks of ice falling down the side of a 2,300-foot-high cliff and then creating a huge dust cloud on the gentle slopes below. Click through for more detailed photos and shots of the orbiting robot that took them. 
What makes the image so striking is that while we've seen the results of things like this on the planets surface, we had yet to capture a live event like this happening.Cameras orbiting Mars have taken thousands of images that have enabled scientists to put together pieces of Mars' geologic history. However, most of them reveal landscapes that haven't changed much in millions of years. Some images taken at different times of year do show seasonal changes from one image to the next, however, it is extremely rare to catch such a dramatic event in action. (Another, unrelated, active process that has been captured by Mars cameras are dust devils.) Observing currently active processes is often a useful tool in unlocking puzzles of the past for scientists studying the Earth. Working from primarily still images, it is harder for scientists studying Mars to rely on this tool. The HiRISE image of avalanching debris is a very rare opportunity to directly do so.
This is the Mars Reconnaissance Orbiter, a spacecraft launched in August of 2005 that was designed to search for water on Mars. It's got the largest camera ever used on a planetary mission on board which is why we keep getting incredibly detailed images of the Martian surface like the ones above. It should keep its primary mission up for another few years, until 2010, before being used as a communications link for future spacecraft. [NASA via AP] -------------------------
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