The Eye of the Sahara..

Canadian astronaut Chris Hadfield (@Cmdr_Hadfield) treated us to another photograph from space but this one looked more like an ancient fossilized shell than a massive geological formation. Originally thought to be the site of an asteroid impact, The Eye of the Sahara — more formally known as the Richat Structure — is a 40km wide, eroded rock dome in the west African nation of Mauritania that has been firmly identified as having a terrestrial origin.