Saturn's moon Enceladus, covered in snow and ice, resembles a perfectly packed snowball in this image from NASA's Cassini mission. (NASA/JPL-Caltech/Space Science Institute)

Scientists have long suspected that Enceladus, Saturn's sixth-largest moon, has an ocean sloshing between its rocky core and icy crust. Now NASA scientists say that they've confirmed that the ocean covers the entire moon.

[Saturn shows off its rings in a stunning new photo]

A paper published this week in the journal Icarus used images from NASA's Cassini orbiter to gather evidence of the massive sea. Scientists analyzed seven years worth of high resolution images to track how the moon wobbles. Based on that analysis, they've concluded that the moon's ice crust must float freely from the core -- which would only be possible if an ocean covered the entire world. 


An illustration of the moon's rocky core, liquid ocean, and icy crust. (NASA/JPL-Caltech)

"This was a hard problem that required years of observations, and calculations involving a diverse collection of disciplines, but we are confident we finally got it right," Peter Thomas, a Cassini imaging team member at Cornell University and lead author of the new paper, said in a statement.

[The wobbling of Saturn’s moon Mimas might mean there’s an ocean sloshing inside of it]

Lots of moons in our solar system seem to have oceans hiding below their ice. And at least one other moon -- the famous Europa, slotted for a visit from a NASA probe in the not-too-distant future -- has an ocean covering its entire surface. But Enceladus is quite exciting regardless: Previous research has suggested that the moon has the kind of geological activity necessary for the evolution of life. Now that scientists are fairly certain that Enceladus's ocean spans the moon's entire surface, the potential habitability of the world has gone way up. 

"This is a major step beyond what we understood about this moon before, and it demonstrates the kind of deep-dive discoveries we can make with long-lived orbiter missions to other planets," co-author Carolyn Porco said. "Cassini has been exemplary in this regard."

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