A spacecraft captured images of "spiders" on the surface of Mars

unique phenomenon that could be mistaken for spiders scuttling across the planet's surface has been spotted on Mars, according to the European Space Agency.

The ESA said in a news release that one of its Mars Express orbiter captured images of the "spiders," which are really just small, dark-colored features that begin to be formed when sunshine falls on carbon dioxide deposited during the planet's winter months. The light causes the carbon dioxide ice at the bottom of the deposits to turn into gas, which eventually bursts through ice that can be up to three feet thick, shooting dust out in geyser-like blasts before settling on the surface, the space agency said.

While the spots might look tiny from space, they're actually fairly large. The ESA said that the patches are as small as 145 feet wide, at their largest, might be over half a mile wide. Below those large spots, the arachnid-like pattern is carved beneath the carbon dioxide ice, the ESA said.