Mars' south polar zoo
Spiders are just one of many strange landforms at the martian south pole.
Scientists suspect that the unique climatic conditions at the Red Planet's south pole plays a role in the variety of strange features the Mars Global Surveyor and Mars Odyssey spacecraft have seen there. Hugh Kieffer, emeritus scientist at the U.S. Geological Survey in Flagstaff, Arizona, has called the region a "zoo" of unusual terrain. Here are a few images of this cryological menagerie.