A scientific study has concluded that Saturn’s moon Enceladus is home to a much larger ocean that previously thought: it likely covers the entire moon, hiding under a layer of ice.

Using Cassini to observe Enceladus over the last couple of years, researchers have concluded that there would be less of a wobble in the moon’s axis if the thick ice shell were connected to the rocky core. Previously, scientists believed that any ocean would be located at the pole, with the planet’s ice crust connected to rock.

Cassini scientists analyzed more than seven years’ worth of images of Enceladus taken by the spacecraft, which has been orbiting Saturn since mid-2004. They carefully mapped the positions of features on Enceladus — mostly craters — across hundreds of images, in order to measure changes in the moon’s rotation with extreme precision.

As a result, they found Enceladus has a tiny, but measurable wobble as it orbits Saturn. Because the icy moon is not perfectly spherical — and because it goes slightly faster and slower during different portions of its orbit around Saturn — the giant planet subtly rocks Enceladus back and forth as it rotates.

The finding is just the latest discovery from the Cassini Spacecraft, which has been exploring the Saturn system since its arrival in 2004. Since its arrival, it discovered three additional moons orbiting Saturn, provided closeup images of Phoebe, has landed a probe on Titan, and provided numerous flybys of other moons orbiting the gas giant.


Image credits: NASA.