Mars’ carbon dioxide atmosphere partially condenses every winter to form polar caps of dry ice. In the spring, the evaporation of the ice is a dynamic process and carves channels into the ground as it escapes back into the atmosphere.

Often these channels are radial in nature, and are colloquially refered to as “spiders,” although the prefered term for these radially-organized channels is “araneiform” which means spider-like.

In this subimage all the seasonal frost is gone, and we can use stereo images or shadow measurements to measure the depth of the channels carved into the ground, typically 1 - 2 meters deep.
Written by: Candy Hansen

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For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.