Ocean discovered below Enceladus

A large, subsurface body of water could exist beneath the ice


This illustration shows Enceladus with an icy shell, rocky core and regional water ocean to the south

Credit: NASA/JPL-Caltech

Scientists have uncovered the strongest evidence yet for the existence of an ocean – complete with rocky seafloor – below the icy surface of Saturn’s moon Enceladus.

Using measurements obtained by NASA’s Cassini Spacecraft during a series of fly-bys over the moon’s south pole, the research group, led by Luciano Iess from the Sapienza University of Rome, were able to analyse the satellite’s gravity and topography, giving a tantalizing glimpse into its interior.

As the gravitational pull of Enceladus slightly altered Cassini’s flight path, by measuring the variations in this effect as the space probe traversed the satellite, the team were able to map the moon's gravitational field.

“The very precise measurements taken by the Cassini probe show a negative gravitational anomaly at the south pole that is, however, not as large as expected from the deep depression detected by the onboard camera,” said Iess.

“Hence the conclusion that there must be a denser material at depth that compensates the missing mass: liquid water, indeed, about seven per cent denser than ice. Comparing gravity measurements with the satellite’s topography, researchers have been able to estimate the size of the water reservoir.”

In 2005, Cassini beamed back incredible images of geysers erupting from the surface of Enceladus and spraying water vapour into space. Ever since then scientists have hypothosised that a large body of water existed below the moon’s surface.

Now scientists believe they have discovered the source, an 8km deep ocean located 30-40km below the satellite’s icy crust. What’s more, if the ocean is in contact with a rocky floor, as is the presumption, the combination of water and silicates could create good conditions for bacteria to flourish.

Discover more Saturnian secrets in our May issue...coming soon!


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