We've built rovers to deal with arid planets like Mars, but what about trips to Titan's hydrocarbon puddles and Europa's ice lakes? NASA's Jet Propulsion Laboratory is working on a robot that'll dive into the frozen water, riding along the underside of the surface of Jupiter's moon. BRUIE (Buoyant Rover for Under-Ice Exploration) is currently being tested out in the Alaskan wilderness, not only to determine if such technology could work, but also to study the water itself, measuring its salt content and temperature. If all goes well, then the first tentative steps towards a launch could begin in a few decades, but until then, you can catch BRUIE in action in the video below.