Saturn's Icy Moon Dione May Have Subsurface Ocean Beneath Rock Hard Crust

NASA's Cassini spacecraft has made some new discoveries when it comes to Saturn's moon, Dione. New findings have revealed that the moon may possess a subsurface ocean beneath its icy surface, which means that Dione could have been active in the past--and may still be active today.

Subsurface seas are nothing new in the world of astronomy. Other bodies in the solar system are thought to have subsurface oceans, including Saturn's moons Enceladus and Titan in addition to Jupiter's moon Europa. These moons are some of the most geologically active worlds in our solar system and have been intriguing targets for scientists that are seeking the building blocks of life.

Before now, though, researchers believed that Dione was an inactive ice ball, orbiting Saturn with little evidence to show otherwise. Recently, though, Cassini's magnetometer has detected a faint particle stream coming from the moon. In addition, images have revealed evidence of a possible liquid or slushy layer under Dione's rock-hard ice crust. Other pictures have shown inactive fractures that are similar to the ones that can be found on Enceladus where they spray water ice and organic particles.

"A picture is emerging that suggests Dione could be a fossil of the wondrous activity Cassini discovered spraying from Saturn's geyser moon Enceladus or perhaps a weaker copycat Enceladus," said Bonnie Buratti of NASA's Jet Propulsion Laboratory in a news release. "There may turn out to be many more active worlds with water out there than we previously thought."

It may seem counterintuitive, but a mountain is what seems to suggest that the moon has a subsurface sea. The mountain, called Janiculum Dorsa, resides on Dione's icy surface. Yet the moon's crust seems to pucker under this mountain. This puckering seems to point to the fact that the icy crust was once warm, and the best way to generate this heat would be through tidal forces.

As Dione orbits closer and further away from Saturn, the moon is stretched and squeezed. This motion is actually amplified due to the nature of Dione's icy crust, which can slide around independently of the moon's core. In fact, the motion generates about ten times more heat than usual.  Yet in order to have this sliding motion, Dione would need a subsurface sea.

These recent findings show that there's a lot more for scientists to learn about Saturn's icy moon. Currently, researchers are trying to understand why Enceladus is far more active than Dione, which seems to have little activity.

Want to learn more about Cassini? Check out the spacecraft's acitivities here.