Image of the Day for April 16, 2026 The circular geologic feature in northwestern Africa can be hard to recognize from the ground, but it is obvious when viewed from space. Apr 16, 2026 View more Images of the Day: 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.…