A large circular formation in the Sahara desert of Mauretania. That is the Eye of the Sahara, also known as the Richat Structure or Guelb er Richat. Walking on it, eye cannot tell you would make much of it, but since it has been spotted from space it has given us various surprising satellite images. The deeply eroded, slightly elliptical dome has a diameter of 40 km and was initially interpreted as a meteorite impact and then a structure formed by a volcanic eruption. Both are impossible because of the lack of a dome of igneous or volcanic rock. Some people now believe it has been caused by uplifted rock sculpted by erosion. The Eye of the Sahara has become a landmark for shuttle crews and gives us some amazing views of our Earth’s surface. PROBA-V captured this 100 m image on May 18, 2016. You can clearly see the circular structure, the equidistant rings of the bull’s-eye as well as the rather featureless expanse of the desert.