Eye of Africa

Posted by Ellen

This rock formation, known formally as the Richat Structure and widely as the Eye of Africa, sits at the southern edge of the Sahara desert in Mauritania. It's a favorite of the astronauts looking down on us, and also a favorite of students of Landsat satellite imagery. It's not a meteor crater or a volcano, but a sedimentary rock formation, layer upon layer of tough, resistant sandstone, brought into sharp relief by softer mudrock that is eroding away. The reason for its perfectly round shape is . . . not well understood.

This image incorporates infrared energy as well as light from the visible spectrum, so the colors are not natural. But twhen the sun is shining on the Sahara Desert as the astronauts sail above it, they do see the Eye of Africa as blueish.