Saturn's Ice Moon Cranks Up the Heat

Enceladus is pumping out enough heat energy to match the output of 20 coal-fired power plants.

THE GIST

- Saturn's moon Enceladus is pumping out 2.6 times as much heat as all the hot springs in the Yellowstone region.

- The discovery raises the prospects of a liquid ocean beneath the moon's icy shell.

- Scientists are at a loss to explain why the moon is so much hotter than previously thought.

Saturn's ice-shrouded moon Enceladus is pumping out more heat from its southern pole than all the hot springs at Yellowstone, and scientists are at a loss to explain it.

The prodigious outpouring of energy significantly boosts the likelihood that an ocean of liquid is sealed beneath the moon's icy surface. Water, in turn, is considered a key ingredient for life.

The new data isn't enough to nail down how large an ocean might exist on Enceladus, or its location beneath the ice.

It does, however, make computer models hard to explain if Enceladus lacks liquid water, lead researcher Carly Howett with the Southwest Research Institute in Boulder, Colo., told Discovery News.

For a long time, scientists thought tidal interactions with neighbor satellites and Saturn would account for about 1.1 gigawatts of energy pumping out of Enceladus. Heat from the natural decay of radioactive materials inside the moon would add another 0.3 gigawatts.

New research from the Cassini spacecraft, however, shows Enceladus is giving off closer 14 gigawatts.

"This is a huge amount of energy that we don't understand," Howett said.

Scientists have known since 2005 that the southern polar region of Enceladus is geologically active, with the hub of activity centered on four 80-mile long, one-mile wide trenches, known as "tiger stripes." Huge plumes of ice particles and water vapor, sprinkled with organic particles, are shooting out into space from the fissures.

"The whole water thing, the eruption of the water is fascinating," Cassini scientist John Pearl, with NASA's Goddard Space Flight Center in Maryland, told Discovery News. "It's the plumes that give you an awful lot of information about the possibility of an ocean. There's some source of energy that's driving these things."

Scientists theorize Enceladus' excess heat may be because the moon used to be in a different orbit that generated a fiercer gravitational tug-of-war with neighboring moons. Energy that built up in the past may be being released now.

No matter what the cause, the realization that the icy moon is pumping out as much heat as 20 coal-fired powered plants has scientists thinking.

"It's clear that whatever is producing the heat, Enceladus meets many requirements for life," Cassini scientist Larry Esposito, with the University of Colorado at Boulder, writes in Astrobiology magazine. "We know it has a liquid ocean, organics and an energy source. And to top it off, we know of organisms on Earth in similar environments."

"This result indicates episodic heating of the moon. The larger heat flow means it is easier to melt water below the surface, but Enceladus may freeze up in between. The implications are therefore mixed for life," Esposito wrote in an email to Discovery News.

"When you look at things like the deep water vents, you can't help but think that something like this is going on on Enceladus," added Howett. "Why not? We see organics, high heat flows. We can postulate until kingdom come, but until we actually go there and have a look we're not going to know."

The research is published in the March 4 issue of Journal of Geophysical Research.

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