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A sea of saltwater is probably hidden inside one of Saturn's icy moons. That's according to some new findings from a spacecraft in orbit around Saturn. If scientists are right this moon might be a watery oasis that could potentially support life. NPR's Nell Greenfieldboyce has more.

NELL GREENFIELDBOYCE: The moon is called Enceladus. It's small, only round 300 miles across, and covered with ice. A few years ago scientists discovered that jets of water vapor and tiny ice particles were bursting out of its surface like giant geysers. These supersonic plumes stream out into space and form Saturn's outermost ring.

Frank Postberg is a scientist at the Max Planck Institute for Nuclear Physics in Germany. He says if you landed a spaceship on Enceladus and got out to look at the plumes you probably wouldn't see them unless the sun was shining the right way.

Dr. FRANK POSTBERG (Max Planck Institute for Nuclear Physics): You only see them when you have the sun in front of you. Then you see the spray and probably even a rainbow.

GREENFIELDBOYCE: No spacecraft has landed there yet. But NASA's Cassini probe is orbiting Saturn and has repeatedly passed through its outermost ring. So Postberg and his colleagues have been using an onboard instrument to study tiny ice grains in that ring that originally came from Enceladus. A report in the journal Nature describes what they found.

Dr. POSTBERG: The most important thing we found is that lots of the grains we identified actually consistent of frozen saltwater. It's saltwater ice.

GREENFIELDBOYCE: Postberg says that strongly suggests that this frigid moon has a source of liquid water, not just ice. Salt compounds are normally found in rock. To get them out of rock you need liquid water.

Now, ever since the plumes of Enceladus were first discovered researchers have been trying to explain them. John Spencer studies the moons of the outer planets at the Southwest Research Institute in Boulder. Colorado. He says some people have argued for mechanisms that didn't require liquid water.

Dr. JOHN SPENCER (Southwest Research Institute): Now it's a lot harder to do that and we're really being forced into, yes, there's liquid water there and, yes, it could be a potential habitat for life. I mean, if a lot of other things went right.

GREENFIELDBOYCE: He says it's not clear what the likelihood is that life could be there. Still, this little moon is starting to seem downright homey. Linda Spilker is deputy project scientist for the Cassini mission at NASA.

Dr. LINDA SPILKER (Project scientist, Cassin mission, NASA): You know, you've got liquid water. It's an alkaline solution that's also favorable for life. You've got other carbon-based compounds and the right building blocks that you would have in there that could be precursors for life.

GREENFIELDBOYCE: Assuming that liquid water is there, it would have to be deep down inside the moon. That's according to Nick Schneider. He's a researcher at the University of Colorado at Boulder. He and his colleagues have been using telescopes to study the vapor coming out of Enceladus rather than the tiny ice grains.

Mr. NICK SCHNEIDER (University of Colorado at Boulder): Because we don't see I guess what you'd say vaporized saltwater in a big ring around Saturn, because we don't see the sodium component of that, we don't think it's saltwater erupting from right near the surface.

GREENFIELDBOYCE: Schneider says there could be a saltwater ocean far below the surface. One that's slowly evaporating into underground chambers that give rise to the plumes.

Mr. SCHNEIDER: So that's possible that there might be some misty caverns underneath the icy crust of Enceladus and a little bit of salty droplets are coming out and a whole lot of salt-free gas is coming out.

GREENFIELDBOYCE: Scientists hope to learn more in November. The Cassini probe will fly by Enceladus and will get closer to the plumes than ever before, just 60 miles above the surface of this alien moon.

Nell Greenfieldboyce, NPR News.

MONTAGNE: This is NPR News.

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