Why go back to Mars? Far from dead, Mars holds untold potential. Nearly half a century of Mars exploration has yielded tantalizing clues that Mars may once have harbored life—and may harbor it still. The extraordinary landing of a revolutionary rover named Curiosity—which successfully touched down inside the Gale Crater—means we have wheels down on the planet once again, in the form of the most sophisticated robot ever to rove the Mars surface. Will NASA's bold mission and this marvel of technology answer some of our biggest questions and usher in a new golden age of exploration? NOVA goes behind the scenes on NASA’s quest to solve the riddles of the red planet.