Enceladus’s ocean may be even better for life than we realised

An ocean of liquid water hidden under the icy crust of Enceladus long ago created this satellite of Saturn. one of the best prospects in search of extraterrestrial life – and it just got more promising. The discovery of heat emanating from the frozen Moon's north pole hints that the ocean is stable on geological timescales, allowing time for life to develop there.

“For the first time, we can say with confidence that Enceladus is in a stable state, and this has major implications for habitability,” says Carly Howett at Oxford University. “We knew there was liquid water and all sorts of organic molecules and heat, but stability was really the last piece of the puzzle.”

Howett and her colleagues used NASA data. Cassini spacecraftwhich orbited Saturn from 2004 to 2017 to capture heat escaping from Enceladus. Its interior is heated by tidal forces as it is stretched and compressed by Saturn's gravity, but until now this heat has only been trapped by leakage from the southern polar regions.

For life to develop in ocean EnceladusMeasurements of heat emanating from the south pole don't account for all the heat gain, but Howett and her team found that the north pole is about 7 degrees warmer than we previously thought. Combined with the heat coming from the south pole, this almost exactly matches the overall value: the ice shell is thicker around the equator, so heat only escapes at the poles in significant quantities.

This means that the ocean must be stable over long periods of time. “It's very difficult to calculate this number, but we don't think it's going to freeze anytime soon or that it's been frozen recently,” Howett says. “We know that life takes time to develop, and now we can say that it has such stability.” In fact find this lifeif he is there, that's a completely different story. But both NASA and ESA are preparing missions to search for it in the coming decades.