image creditThe Sahara Desert, in which the Richat Structure is situated, does look rather featureless from above. So when astronauts glimpsed this prominent almost circular mark - with a diameter of almost 50 kilometers - it piqued their interest. It is also occasionally called the Eye of Africa - and you can see why.
It was for a number of years thought to be the impact crater of an ancient meteor strike against the Earth. However, it is now thought to be what is known as a symmetrical uplift which, over the millennia has become visible due to the erosive effects of desert winds.
(thanks Robert-John)The Presurfer
