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This series of images shows carbon dioxide ice sublimating (going directly from a solid to a gas) inside a pit at Mars' south pole. As ice is lost from the steep walls of pits like this, it reforms on nearby flat surfaces. Each frame of the animation was taken by the High Resolution Imaging Science Experiment camera (HiRISE) on NASA's Mars Reconnaissance Orbiter.

The images used in this animation were taken between 2007 and 2013. The walls of the pit are about 656 feet (200 meters) across.

The University of Arizona in Tucson operates HiRISE, which was built by Ball Aerospace & Technologies Corp., in Boulder, Colorado. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.