The one-ton, car-sized Curiosity rocketed from Kennedy Space Center Saturday. The vehicle is on a two-year mission to determine whether life could have existed on Mars.With the roar of an Atlas 5 engine, NASA began its boldest venture yet to another planet, sending its Mars Science Laboratory on an eight-month journey that is expected to provide Earth with new and more detailed information about whether the red planet is -- or ever has been -- hospitable to life.