There is an ice sheet at the North Pole of Mars that is a few miles thick at its center. At some places (like in this image) it ends in steep cliffs that can be about 800 meters (2,600 feet) high.
The slopes of these cliffs are almost vertical which causes slab-like blocks of ice to break off and crash down to the surrounding plains. Dense networks of cracks cover these icy cliff faces making it easier for these blocks to break free. We’ve seen new debris at the base of many of these cliffs appearing between successive HiRISE images, so we regularly monitor sites like this to check for new blocks that have fallen. Understanding how these cliffs are formed helps us understand the climatic record stored in the ice sheet itself.
Have any new blockfalls occurred here? Try and compare this image with ESP_018959_2635 (taken almost exactly one Martian year ago) and check for yourself!
Written by: Shane Byrne (11 July 2012)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_027451_2635
Image: NASA/JPL/University of Arizona