Portal:Mars/Selected article/April 2008
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Martian "spiders" are geological formations thus far unique to the south polar region of Mars. These structures have not been found in the north polar region or any other region of Mars to date. They appear as the carbon dioxide ice cap at the Martian south pole sublimates into carbon dioxide gas during the Martian spring and the surface below is revealed.
The formations, when viewed individually, form a round lobed structure reminiscent of a spider web. They generally radiate outward in lobes from a central point. The central point is sometimes, but not always, a crater. The formation is similar in its branching appearance to a diffusion-limited aggregation. Similar branching patterns are also seen in watershed erosion regimes as well as the branches, roots and leaf veins of plants.
