Callisto, too, may have an ocean beneath its icy surface, though this is less certain.

ECONOMIST: Galileo and Jupiter

Even then, the sled has precious little lateral stability, and when it gets crossed up even slightly on a groomed, icy surface, it catches an edge and flips over.

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The researchers were able to draw parallels between our planet and Saturn's hazy moon, suggesting that similar geological processes may have altered Titan's icy surface in the recent past.

MSN: Saturn's moon Titan may have seen Earth-like erosion

This unlikely sounding collaboration is taking place between researchers interested in exploring Lake Vostok in Antarctica, which is sealed off below several kilometres of ice, and planetary scientists, who see such exploration as a possible dress rehearsal for a future robotic mission to Jupiter's moon Europa, whose icy surface is thought to conceal vast oceans that might harbour extraterrestrial life.

ECONOMIST: Planetary pretenders

Pictures of the icy satellite Enceladus suggest its surface splits and spreads apart - just like the ocean floor on our planet splits to create new crust.

BBC: Enceladus has 'spreading surface'