A lot of UFO fans are obsessed with strange-looking rocks on Mars, but there are plenty of oddball formations on Earth worth getting excited about, too. 

International Space Station cosmonaut Anton Shkaplerov posted an intriguing photo of an Earth landscape and then promptly explained away the visual weirdness of the shapes below.

Shkaplerov's Twitter image from Tuesday shows a scenic spread of land with vein-like features and a semi-orderly spread of dark round shapes. Some are on a grid pattern, while others seem to be scattered around like fallen confetti.

Taken out of context and with a proper dose of fevered imagination, you might think those circles comprise a well-used set of landing sites for alien visitors. After all, the classic UFO is round and we have a long history of human fascination with crop circles. 

But Shkaplerov debunks all that speculation. "This giant fields of circles on the Earth below are not UFO landing sites, but are just fields that are being served by center-pivot irrigation systems," he writes. 

The photo shows an agricultural area in the northern reaches of Saudi Arabia where deep wells tap an ancient aquifer and farmers grow fruits, vegetables and grains. NASA traced this area through satellite images and notes, "The thirsty plants that rise out of the Arabian desert are quenched by water that dates back to the last Ice Age."

That's may not sound quite as exciting as UFOs, but it's fascinating to see the marks left by human hands on what would seem to be an inhospitably arid region.