Mars probe spots "spider" shapes in Martian Inca City

The European Space Agency reported a surprising finding in a region of Mars known as Inca City, in which dark shapes resembling spiders were discovered by the agency's Mars Express orbiting satellite. The strange arachnid shapes are actually geologic features formed by channels of carbon dioxide gas that originate as the weather warms in Mars' Southern Hemisphere for that planet's spring. This causes them to create black branches measuring from 0.03 to 0.6 miles across (45 meters to 1 kilometer) …