Secret Cold War Sonar Tech Is Being Used to Map Underwater America

Space may be the final frontier of exploration, but there's plenty of Earth left unmapped, too—from the giant canyon recently discovered beneath Greenland to American waters that have been left largely unexplored. But that’s quickly changing, thanks in part to Bob Ballard’s latest project. » 10/17/13 3:43pm 10/17/13 3:43pm