There are several candidates for extraterrestrial life in our solar system. Moons such as Europa and Titan seem the likeliest targets so far, but Saturn’s moon Enceladus has today been bumped to the top of the list due to the discovery of a liquid water ocean below the icy surface. This announcement comes from lead author Luciano Iess and a team of Italian and American scientists. The team’s paper was published in Science.

Historically, Enceladus hasn’t been regarded as a very exciting place. It was thought to be an inactive, relatively boring moon composed of ice and rock; materials that are common in the outer solar system.

In 2005, the Cassini spacecraft took images of icy water geysers at the moon’s South Pole. This was the first indication that Enceladus could have water, and thus, the potential for life. Liquid water is crucial for life as we know it, so it becomes extremely exciting when it was found. 

The researchers have been analyzing the subsequent data that has been collected from Cassini since the discovery of those geysers nearly a decade ago. The team discovered that in the south, there is a substance below the ice that has a greater density than the ice. The moon experiences fluctuations in gravitational pull from Saturn and all of the other 50+ moons. These tidal forces pull and flex the ice, causing it to rub together. It seems reasonable that the friction caused the ice within the moon would have melted into liquid water. The surface ice would remain in tact (and repair fairly quickly) due to the extremely cold temperatures.

There are some uncertainties to be considered, though. Enceladus is incredibly small, and at about one-seventh the diameter of our moon, it lacks the necessary gravity to maintain an atmosphere. Scientists cannot confirm the internal structure of the ice and if the Lake Superior-sized ocean, which is hidden miles under the ice, is connected to the geysers, though they do suspect it is. The internal “plumbing” of Enceladus will require further research.

Even though the scientists do not have direct proof of the internal liquid water ocean, the indirect evidence that they have acquired has left the team feeling “very comfortable” with the conclusion, according to Iess. It is currently undetermined what the next steps will be with investigating water on Enceladus, as Cassini is scheduled to spend the next part of its mission investigating two other Saturnian moons, Titan and Dione.