Mars spiders have arrived on Earth. But fear not, arachnophobes — these "spiders" aren't actual arachnids, but spider-like geological formations on the Martian surface. And NASA has just recreated them in a lab.
Scientists first discovered these spider-like features, or araneiform terrain, on Mars in 2003 while studying images from orbiters. They're much, much larger than spiders, though; they can stretch more than half a mile (1 kilometer) end-to-end, and they can have hundreds of "legs."
