"Hot spot" found on one of Saturn's moons

LONDON (Reuters) - There is a hot spot on one of Saturn's moons which should not be there and has yet to be explained, scientists said on Tuesday.

It is located at the south pole of Enceladus, a moon with a diameter of just 500 km (310 miles) which orbits Saturn at a distance of around 238,000 km.

The hot spot is unusual because it occurs at the pole, scientists said. Usually, the hottest part of any planet or moon is around the equator, as is the case with the earth.

This suggests that the heat at Enceladus' southern pole is generated from within, said scientists from the Cassini-Huygens mission to Saturn and its moons.

But they acknowledged they had no idea how.

"It shouldn't be that warm," said John Spencer, one of the scientists working on the project.

"It's like flying past Antarctica and finding that it's warmer than the earth's equatorial regions. It's that strange."

Spencer, of the Southwest Research Institute in Colorado, the United States, is one of a group of scientists examining data sent back to earth from the Cassini spacecraft, which was launched in 1997 to examine Saturn.

The spacecraft has flown past Enceladus three times -- most recently on July 14 when it passed within just 175 km of the small, icy orb.

The scientists expected to find that the temperature was around 80 degrees Kelvin (-193 degrees Celsius, -316 degrees Fahrenheit) at its hottest point, which they assumed would be near the equator.

Instead, they found that the heat was concentrated at the south pole, where the temperature hit 91 degrees Kelvin near a series of fissures, or "tiger stripes" on the moon's surface.

"It is an extremely conspicuous hot region," Spencer told a news conference. "Something is different about that area."

The scientists have come up with two theories to explain the hot spot. The first is that the heat comes from decaying radioactive material below the moon's surface and the second is that it is caused by gravitational tides.

But they say neither theory adequately explains the heat.

"We don't have anything we could call a complete hypothesis yet," said Torrence Johnson from NASA, which is working on the project alongside the European and Italian space agencies.

The team says the hot spot suggests there might be volcanoes and geysers on Enceladus.

If this is true, it would be one of only three "active" moons known to man. The others are Io, which orbits Jupiter, and Triton, which circles Neptune.

The Cassini spacecraft has been sending spectacular images back from Saturn, its rings and its moons since last year, when it reached the planet. It also launched a probe which landed on the surface of Titan, another of Saturn's 31 known moons.

The Hot Poles of Enceladus

Image courtesy of NASA/JPL-Caltech

The unexpected hot spot around Enceladus' south pole is another indication of electric currents coursing through Saturn's moon and connected with the electric circuits that compose Saturn's plasma sheath.

The NASA press release reports that this image "startled" scientists. The hot spot around Enceladus' south pole is "very difficult to explain if sunlight is the only energy source heating the surface." The only other likely heat source available to conventional theorists is internal heat, but they are "unsure how the internal heat reaches the surface."

Close-up images reveal a series of somewhat parallel fractures that are the centers of the heat. NASA scientists speculate that internal heat escapes through these fractures and evaporates the ice along them, thereby generating Enceladus' thin atmosphere of water vapor, which seems to be concentrated over the south pole. Water escaping from the atmosphere may be the source of the icy material in Saturn's E ring, the largest ring, in which Enceladus orbits.

The fractures are only 1 to 2 kilometers wide but extend over 100 kilometers in length. Proponents of the Electric Universe recognize this form as the typical electrically excavated rille. They also notice the correspondence of Enceladus' hot pole with hot spots around the poles of other planets and moons. The electrical circuits in Saturn's plasma sheath will include a "neutral sheet" and ring currents (plasma toroids) in the plane of the rings, and Enceladus orbits within those currents.

In this respect, Enceladus is similar to Io, orbiting within an equatorial toroid around Jupiter and connected to Jupiter's auroral circuit by a polar flux tube. As Peratt and Dessler have shown in Filamentation of Volcanic Plumes on the Jovian Satellite Io, A. L. Peratt and A. J. Dessler, Astrophys. Space Sci. 144, pp. 451-461, 1988 (1M)., Io's "volcanoes" are "plasma gun" discharges in the electric circuits flowing through and around Io.

In the electric view, the warm rilles and hot pole are electrically heated. The water vapor from the rilles is being electrically "machined" from them. A similar process should be occurring at the north pole, where the electric current flowing through Enceladus returns to Saturn's sheath circuit.

NASA scientists have noticed the "bending" of Saturn's magnetic field around Enceladus "due to electric currents generated by the interaction of atmospheric particles and the magnetosphere of Saturn." But their blind spot with regard to plasma behavior leads them to insist that the electric currents "don't do anything."

The past century of plasma research demonstrates just the opposite. Experimental scientists from Birkeland to Alfven confirm the insight of Heraclitus in the Fifth Century BCE: It is the thunderbolt that steers the universe.

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