Four centuries and one year after the Mayflower departed from Plymouth, England, on a historic sea journey to America, another trailblazing vessel with the same name has set off to retrace the voyage. This Mayflower, though, is a sleek, modern robotic ship that is carrying no human crew or passengers. It's being piloted by sophisticated artificial intelligence technology for a trans-Atlantic crossing that could take up to three weeks, in a project aimed at revolutionizing marine research. IBM, which built the ship with nonprofit marine research organization ProMare, confirmed the Mayflower Autonomous Ship began its trip early Tuesday.