NASA Spacecraft To Skim Past Saturn's Icy Moon

Oct 27, 2015
Originally published on October 28, 2015 3:25 pm

A NASA probe will hurtle past Saturn's moon Enceladus on Wednesday, coming to within just 30 miles of the surface.

In the process, it will sample mist from a liquid ocean beneath the frozen surface. Doing so may provide clues about whether the ocean can support life.

At just 314 miles across, researchers originally expected Enceladus to be a tiny ball of solid ice. But thanks to NASA's Cassini probe, they now know it's somewhere really special.

"We're very confident there's a liquid ocean underneath Enceladus' crust," says Linda Spilker, a project scientist for Cassini, which has spent the past 11 years orbiting Saturn.

Cassini has previously sent back images of water literally spewing out of the moon's south pole. Now on its 21st visit to Enceladus, the spacecraft will get closer to the geysers than it ever has before. The spacecraft will streak through the icy mist at 19,000 miles per hour. The entire encounter will last under a minute.

The real goal here is to figure out whether the hidden ocean that feeds those geysers could support life. Cassini will look for hydrogen gas burbling out of hot vents on the ocean floor.

"By measuring the amount of hydrogen coming out, we think we can better understand the amount of energy available in this ocean, this potential habitat for life," Spilker says.

On Earth, there's definitely life in hydrothermal vents. Cassini won't be able to tell whether the same is true on Enceledus, but if there is, Spilker says, it's not much of a life. The alien beings would cling to their vents, in darkness, far beneath the icy surface.

"[They] wouldn't know about the sun that was up there," Spilker says. "Or anything else that's going on."

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And in other news, later today, a NASA spacecraft will skim past a small icy moon of Saturn. As NPR's Geoff Brumfiel reports, the goal is to learn what lies beneath the surface.

GEOFF BRUMFIEL, BYLINE: Saturn has dozens of moons, but this one, called Enceladus, looks really special.

LINDA SPILKER: We're very confident there's a liquid ocean underneath Enceladus' crust.

BRUMFIEL: That's Linda Spilker, project scientist for the Cassini spacecraft that's passing Enceladus today. Cassini has previously sent back images of water literally spewing out of the moon's South Pole. Spilker still remembers the first time she saw it.

SPILKER: Standing around the computer screen, looking at the pictures and the excitement of what does that mean that a moon this small could actually be having, you know, geysers of material coming out of its South Pole.

BRUMFIEL: Cassini's now making its 21st visit to Enceladus, and it'll get closer to the geysers than it ever has before. The spacecraft will pass just 30 miles from the surface, streaking through the icy mist at 19,000 miles per hour. The real goal here is to figure out whether the hidden ocean that feeds those geysers could support life. Cassini will look for hydrogen gas burbling out of hot vents on the ocean floor.

SPILKER: By measuring the amount of hydrogen coming out we think we'll be able to better understand the amount of energy available in this ocean, this potential habitat for life.

BRUMFIEL: On Earth, there's definitely life in hydrothermal vents. Cassini won't be able to tell if the same is true on Enceladus. But if there's life, Spilker says it's not much of a life. The aliens would have to cling to their vents far beneath the icy surface. None of them would ever see the sun. Geoff Brumfiel, NPR News. Transcript provided by NPR, Copyright NPR.