NASA is developing underwater robotic explorers that will search alien oceans for signs of life. The drones will be able to think for themselves as they navigate through the icy seas believed to exist beneath the crust of Europa, Jupiter's moon. Nasa scientists believe that water – the ingredient for life – can be found beneath Saturn's Dione and Ganymede too. There's compelling evidence that hidden oceans on dwarf planest Ceres and Pluto could also be home to mysterious extra-terrestrials. "Depending on the exact mission concept under consideration, autonomous underwater vehicles exploring ocean worlds will need to operate autonomously for days to months.