Bulls-eye in the desert: The Richat Structure from above

Today's Image of the Day from the European Space Agency features a distinctive circular pattern in the Sahara Desert that has sparked curiosity for many years.  The formation, known as the Richat Structure or the eye of the Sahara, appears as a wide ringed mark in northern Mauritania. It is located in the Adrar Region, a dry and wind-shaped landscape.  People once suspected a meteor carved the rings into the ground, but studies eventually shifted to a different explanation.  Evidence now points to...