The water body, believed to be locked within Europa’s icy outer shell a few kilometres from the surface, offered one of the best hopes yet of finding life beyond the Earth, the researchers said.

Computer simulations based on the images of two circular bumpy regions on Europa’s surface captured by Nasa’s Galileo spacecraft, suggested that an “ice cave” might be buried near enough the surface to support life, with a floating “cap” leading to a cave of salty slush, the Daily Mail reported.

On Earth, similar features in the Antarctic are caused by briny seawater penetrating and weakening ice shelves. They are also present in Iceland, where glaciers are heated from below by volcanic activity.

Scientists have long suspected that a liquid or slushy ocean exists under Europa’s surface, warmed by the tidal forces of Jupiter’s powerful gravity. Theoretically, a liquid water ocean could provide a suitable habitat for life — but only if it was not too far from the surface.

Experts disagree about how thick the layer of covering ice is. The new research, based on images from the Galileo probe, suggested that water “lenses” could lie as little as three kilometres below the bottom of the surface crust.

Lead scientist Dr Britney Schmidt, from the University of Texas, said: “One opinion in the scientific community has been, ‘If the ice shell is thick, that’s bad for biology — that it might mean the surface isn’t communicating with the underlying ocean’.

“Now we see evidence that even though the ice shell is thick, it can mix vigorously. That could make Europa and its ocean more habitable.”