At the edge of Mars’ permanent North Polar cap, we see an exposure of the internal layers, each with a different mix of water ice, dust and dirt. These layers are believed to correspond to different climate conditions over the past tens of thousands of years.
When we zoom in closer , we see that the distinct layers erode differently. Some are stronger and more resistant to erosion, others only weakly cemented. The strong layers form ledges.
Written by: Candy Hansen (audio: Tre Gibbs) (24 August 2016)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_045604_2645
Image: NASA/JPL/University of Arizona