Video: NASA rover roams the underside of frozen lakes.

NASA’s Jet Propulsion Laboratory is working on a rover that can be inserted under an ice sheet, before using its buoyancy to enable it to be driven untethered underwater, using the underside of the ice for traction.

One day such a system could be used on the surface of Jupiter’s moon Europa, but for now it’s being tested in Alaska, measuring salt content and temperature of the water there.