You've probably seen pictures of Jupiter's mysterious Great Red Spot which actually is a gigantic storm about two to three times the size of our entire planet [source: Choi]. But when viewed from space, Earth has a similarly strange-looking surface feature.
The Richat Structure in Mauritania is a gigantic circular swirl, about 30 miles (50 kilometers) in diameter, that forms a bull's-eye in an otherwise featureless expanse of west African desert. When astronauts first noticed the Richat Structure in the 1960s, it was believed to be a crater left behind by an immense meteor, because of the uniformity of its curves. But scientists now think that it's a rock formation of Paleozoic quartzites, laid bare by erosion [source: NASA]. Either way, though, it's plenty strange looking.