Deep heat powers once-in-a-billion-year volcanoes on icy moon

January 11, 2010, Macquarie University

( -- New research by Macquarie University planetary scientist Dr Craig O’Neill and US colleague Francis Nimmo has found the answer to an apparent cosmic contradiction.

The mystery relates to Saturn’s tiny ice . Until relatively recently, very little had been known about Enceladus, however scientists expected it to be a cold and dead place given its physical characteristics.

Then NASA’s 2005 flew by Enceladus at close range, and straight into an active field.

Research performed by O’Neill and co-author Nimmo from the University of California, Santa Cruz is published online today by Nature Geoscience. The project was partly funded by the NASA Outer Research program.

In their article, the scientists show how their demonstrate that over billions of years the pent up energy from the tidal forces Enceladus experiences on its orbit around Saturn eventually melt its interior ice, and result in a pulse of crashing ice plates and ice volcanoes, or cryovolcanism.

“Enceladus was an enigma,” said O’Neill, who was lead scientist on the study. “Somehow it seems to be pumping out more energy than it gets, which would violate the laws of thermodynamics,” he said.

“We knew from the prior Voyager missions that Enceladus might have a complex geology, but most people thought that was in the past. Yet it turns out this 500km-across ball of ice is one of the most active moons or planets in the .”

The pent-up heat - enough to melt the interior, and possibly sustain a ocean under the ice - would be released as one catastrophic event around every billion years or so. Cassini just happened to fly into it, O’Neill said.

“Eventually you reach a critical point, and the whole thing just blows,” he said.

The ice sheets would flow like glaciers, the heat causing geysers to pop up all over the active surface, he added.

It turns out the little worlds like Enceladus are among the most interesting, which makes us reflect on what we think we know of the processes that shape Earth’s interior.”

Explore further: Icy moons of Saturn and Jupiter may have conditions needed for life

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5 / 5 (3) Jan 11, 2010
The likelihood that Cassini just stumbles onto a once-in-a-billion event is remote. I suggest that scientists continue to study the subject.
2 / 5 (2) Jan 11, 2010
"The ice sheets would flow like glaciers, the heat causing geysers to pop up all over the active surface, he added."

The "geysers" are located on the south pole only. No evidence of "geysers" active anywhere else on the surface. How does their model explain that? Wouldn't centrifugal force cause more internal pressure around the equator increasing the probability of "geysers" occurring there as opposed to the poles?

Gee, aren't we lucky to just happen to witness this once in a billion year event. What are the odds on that?

Given the plasma environment around Saturn and the fact that there are field aligned ion beams propagating from Saturn into the "geyser" region of Enceladus, it makes sense to consider the source of these "geysers" to be the electromagnetic plasma environment ripping ions and other material from the icy surface. No liquid required.

not rated yet Jan 11, 2010
too bad it doesn't orbit mars. once in a billion years might have been enough to let it stay warm.
5 / 5 (1) Jan 11, 2010
Could this be a cooler version of the 'overturn' suggested for Venus' surface ??

( Daren't say 'similar' in this context due different heat sources, materials etc ;-)
not rated yet Jan 11, 2010

You could use 'similar', we'd just need a few caveats.
In this case solid ice "crust" is keeping in the heat until a critical point.
And with Venus, the heat is kept in by (we assume) the lack of plate tectonics, until the whole surface is reformed in the massive lava flow event.

Here we have yet another example of planetary-scale fluid dynamics (and thermo).
5 / 5 (1) Jan 11, 2010
I suspect the tidal forces keep it in a state of vulcanism and this is not a rare event but common to that world. If a thing can be imagined it exists somewhere. I betcha!
not rated yet Jan 12, 2010
As posted earlier, seeing evidence of cryovolcanism on Triton and Io makes me wonder how lucky we really got wrt Enceladus?

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