NASA scientists have confirmed the existence of a gigantic lake in what is now the middle of the Sahara. I've read in a few places that earlier radar mapping missions (STS-2 and -41G) were not really the pure science they were advertised as, but instead were subtle cold war demonstrations meant to prove we had the means to detect silos no matter how well the Soviets hid them. Dunno if that's true, but it makes for a neat story.