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 (30 September 2009)
This is a stereo pair with ESP_014282_0930 .
More info and image formats at http://hirise.lpl.arizona.edu/ESP_014413_0930
Image: NASA/JPL/University of Arizona