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Eyeing the Richat Structure

Eyeing the Richat Structure

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The Richat Structure appears as a giant “bull’s eye” on a plateau in Mauritania in this mosaic, composed of images captured by the OLI (Operational Land Imager) on Landsat 9 and Landsat 8 on March 5 and March 6, 2026, respectively.

NASA Earth Observatory/Lauren Dauphin

In a remote part of northern Mauritania on the Adrar Plateau lies a desert landscape rich in human history. This region of northwestern Africa is sprinkled with Paleolithic stone tools, Neolithic cave paintings, and the remains of medieval towns once used by caravans crossing the Sahara Desert.

When viewed from space, the landscape appears to be shaped most prominently by natural forces. Wind sculpted the seas of colorful sand dunes and scoured plateaus capped with dark desert pavement, while ancient flowing water carved valleys and networks of dried river channels.

But the region’s most eye-catching feature when seen from above is the Richat Structure—a large geologic formation made of concentric ridges on the eastern side of the plateau. French geographers first described the feature in the 1930s, calling it the Richat “buttonhole.” NASA astronauts Ed White and James McDivitt helped bring wider global attention to what became known as “The Eye of the Sahara” after photographing it during their history-making Gemini IV mission.

The 40-kilometer-wide (25-mile-wide) structure was initially thought to be an impact crater because large meteors can produce circular features on Earth’s surface. However, researchers later showed that it is actually a deeply eroded geologic dome formed by the uplift of rock above an underground intrusion of igneous material. Over time, differing erosion rates among rock types in the exposed upper dome led to the development of circular ridges known as cuestas. The orange and gray colors reflect differences in sedimentary and igneous rock types across the structure and the surrounding landscape.

NASA Earth Observatory image by Lauren Dauphin, using Landsat data from the U.S. Geological Survey. Story by Adam Voiland.