Jupiter’s Moon Europa

A bit smaller than our Moon, icy Europa is the second innermost of Jupiter’s four large moons. Being farther away from Jupiter, Europa has tidal kneading less extreme than that experienced by Io but still considerable. This kneading melts Europa’s subsurface ice to form a 50-mile-deep ocean hiding below a 6-mile-deep surface layer of ice. Cracks in the ice layer are visible in this movie, looking much like those in the Antarctic shelf ice and suggesting movement over a mysterious ocean below. There is more water in Europa’s ocean than in all the oceans of Earth. One wonders whether life could be lurking there. On Earth, tube worms and other organisms thrive in extreme environments at the ocean floor, on energy supplied by hydrothermal vents called black smokers. This could happen on Europa, supporting life-forms isolated from the Sun’s energy. A probe could melt its way through the ice layer and release a submarine to explore.