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Plumes of icy material extend above the southern polar region of Enceladus.
Credit: NASA/JPL/Space Science Institute

Mar 16, 2007
Enceladus Plumes Explained?

A new NASA hypothesis, said to account for the mysterious “geysers” on Saturn’s moon Enceladus, presents a familiar paradox. What is the value of a model that rests entirely on imagined processes hidden from view?

It was about a year ago that we reported on NASA’s quest to resolve the mystery of the high-speed jets erupting from the surface of Saturn’s icy moon Enceladus. The jets are focused on the south polar region of the moon, which was supposed to be the coldest place on a long-dead body. Enceladus is just 504 kilometers in diameter – too small to support significant internal heating. NASA scientists, however, work within a narrow frame of reference. If dynamic activity observed on planets, moons, and comets cannot be explained by solar radiation, just about the only thing left to account for it is something going on beneath the surface.

Reflecting on the mystery of the Enceladus plumes, the Cassini mission co-investigator John Spencer stated, "This is as astonishing as if we'd flown past Earth and found that Antarctica was warmer than the Sahara.”

Similarly, a NASA news release announced, “The rare occurrence of liquid water so near the surface raises many new questions about this mysterious moon.”

In response to this, we wrote, “Water ‘so near the surface’? All we can see is ice on the surface—and icy plumes 480 kilometers high. But conditioned perception declares that liquid water must be present under the surface (like a Yellowstone geyser), in order for it to erupt in high-speed jets. The prior theoretical framework remains untouched even in the face of a stunning surprise.”

If any more evidence is needed to confirm the intense grip of theoretical assumptions today, it is given to us by the most recent speculation announced by NASA’s Cassini mission, entitled “A Hot Start Might Explain Geysers on Enceladus.” The report announces a new model developed under the direction of Dr. Dennis Matson, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, California. This model, laying one speculation upon another, proposes that, "Deep inside Enceladus…we've got an organic brew, a heat source and liquid water..."

The new hypothesis attributes the imagined internal heat to “the rapid decay of radioactive elements within Enceladus shortly after it formed.” This, according to NASA, “may have jump-started the long-term heating of the moon's interior that continues today.”

"Enceladus is a very small body, and it's made almost entirely of ice and rock. The puzzle is how the moon developed a warm core," said Dr. Julie Castillo, the lead scientist developing the new model at JPL. "The only way to achieve such high temperatures at Enceladus is through the very rapid decay of some radioactive species."

A layperson reading these comments may not be aware of the strains this “puzzle” places on planetary science. In trying to explain energetic jets from the icy moon, NASA scientists have had to resort to events so remote in time and so far from view as to have no testable component. Contrast this with the electrical explanation offered by Wallace Thornhill and his colleagues. Here, the proposed electrical discharge events will be easily confirmed if NASA will simply look for them. They will be seen in the movement of the discharge across the surface, the channels carved into the surface by the discharge, the acceleration of ejected material, and the localized surface heating and extremely high temperatures of the focused arcs themselves. The latter feature, predicted exclusively by the electrical model, requires only that the thermal instruments capture the discharge activity at sufficient resolution. The findings will immediately exclude all prior attempts to explain the plumes through an internal heat source.

Of course, the electric interpretation of the Enceladus plumes does not stand in isolation. It is the perfect complement to other electrical events occurring on Saturn itself and evidenced across the landscape of Saturn’s largest moon Titan. For background on electrical activity on Saturn, see Saturn’s Monstrous Polar Storm, Electric Lights on Saturn, and The Electrical Heating of Saturn. And for background on Titan, see Methane Lakes on Titan, and Titan and its Rilles. Additionally, it is worth remembering that the inability of NASA scientists to see the evidence for electrical activity on Enceladus is, in many ways, a replay of the difficulty other NASA scientists had in seeing the electrical activity on Jupiter’s moon Io, even after eminent astrophysicists and plasma scientists (Thomas Gold, Anthony Peratt, and Alex Dessler) had given them sound scientific reason for seeing this electrical activity.
 

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