NASA has, for the moment, killed funding for research leading to an underwater probe for Europa’s suspected saltwater ocean. But it’s possible that this is a good thing. proposes that U.S. Navy-funded research into underwater gliders could offer a superior means of probing Europa, exploring Venus, and even diving into the methane/ethane seas of Titan.

NASA wanted a big battery and propeller machine under the ice of Europa, but that might break down, stir up water that should be left undisturbed, and leak lubricants into a pristine research environment. The navy wants gliders with internal actuators because they have no flaps or propellers, no lubricant, and one already exists that could “fly” under the Pacific from Seattle to Tokyo on a penlight battery! Another model uses no batteries for locomotion at all, but instead taps heat gradients.”