A giant eye left by a meteorite in the Sahara desert

A photo taken by astronauts in 2013 revealed a giant eye-shaped impact crater in the Sahara desert, surrounded by shifting sand dunes that can move more than 30 meters per year, according to Live Science. The Aorounga structure is a 12.6 km wide impact crater located in the southeastern Sahara, north of Chad. The crater consists of two circles that give it an eye-like appearance. The inner circle with the thalamus in the middle looks like an eyeball, while the outer circle resembles an eyelid. The circles rise 100 m above the surrounding ground but have eroded strongly over a long period of time, similar to many other ancient impact craters. Most likely it was originally taller and wider.

Experts believe the structure formed about 345 million years ago and was created by a meteorite 600 meters in diameter, according to estimates from the Lunar and Planetary Institute. An impact this large is known as a “city-destroying meteorite”, which could cause widespread damage across northern Africa, even accelerating impacts on global climate.

The structure also has several dark straight lines crossing the two circles. It’s part of large wind troughs called yardangs, according to the US Geological Survey. Such a wind trough can reach a height of 30 m above the ground, stretching for dozens of kilometers throughout the surrounding area. A cluster of five crescent-shaped dunes is clearly visible in the photo. Over time, they are pushed across the desert by winds and move in opposite directions, according to NASA’s Earth Observatory.

By comparing their positions in this photo with satellite images of the same area in late 2003, researchers were able to calculate exactly how far they had moved in just over nine years. From left to right, 5 sand dunes numbered 1, 2, 3, 4, 5 have moved 316 m, 275 m, 405 m, 318 m and 381 m. The most moving sand dunes are numbers 3 and 5 which are also the smallest. Dunes smaller than them could be wiped out within a decade.

Researchers have long known that crescent-shaped sand dunes move across the Sahara desert. However, scientists are only just beginning to calculate the distance they travel by tracking their movements using satellite images. They hope to use their new achievements to predict sand movements, helping to reduce the problem of sand dunes blocking roads and covering agricultural land.