NASA has begun exploring new ways to explore planets through their Innovative Advanced Concepts program (NIAC). One of these is a robotic eel, which they can use to travel across Jupiter's gas giant of a moon 'Europa.'
This amphibious rover is rather worm-like in its movements, and can recharge itself using "locally changing magnetic fields." This is a good alternative to solar, on a moon where you can't guarantee the amount of sun required for it.
This is one of 15 different proposals, each awarded $100,000 in funding for phase one of NIAC. If they move into phase two, they will get a further $500,000. These ideas all range from a pair of unmanned gliders that can work to keep each other in the Earth's atmosphere for years, to "robot crawlers, hoppers and soccer-ball style buckey bots" built to look for water & nitrogen with a cool acronym 'CRICKET:' short for Cryogenic Reservoir Inventory by Cost-Effective Kinetically Enhanced Technology.
One thing to emphasise, these ideas are still a long way from reality, but the fact NASA has invested heavily in the project shows promise. We're pretty excited!