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Sep 29, 2004
Big Holes in Little Moons

Large craters observed on two small moons orbiting Saturn surprised many astronomers. Presumably, the impacts should have shattered the tiny bodies. But from an Electric Universe vantage point, something much different than “impact” occurred.

Mimas and Tethys are two small moons orbiting Saturn. Since their discoveries in 1789 and 1684 respectively until the Voyager probes passed by them in 1980, we could see them only through telescopes and then only as two moving dots of light. Even the Voyager images (above Mimas left, Tethys right) are very tiny, taken from hundreds of thousands of miles away.

Now Cassini could examine them close-up (although no direct flybys of either moon are scheduled for the 4-year Cassini mission.) Astronomers were surprised by the Voyager images of immense craters and cliffs. Mimas is only about 400 kilometers (250 miles) across, but the crater Herschel is dug out of 130 of those kilometers (in projection), covering 3% of Mimas' surface. To reach the surface from the floor of Herschel, you would have to climb up 10 kilometers (6 miles) of steep cliffs--more than climbing Everest from sea level. (If you wanted a less strenuous climb, you could ascend Herschel's central peak--at 6 kilometers, it would match an ascent of Kilimanjaro.) Tethys is over 1000 kilometers (600 miles) in diameter. Its large crater, Odysseus, at 400 kilometers (250 miles) across, covers 4% of Tethys' surface. The floor of the crater is convex and matches the curvature of the surface. This means that in the middle of the crater, Odysseus' floor protrudes beyond the crater's rim.

Several astronomers expressed surprise that the impacts they assumed caused the craters didn't shatter the tiny moons (this comment is made about other moons and asteroids with disproportionately large craters, too.) From the Electric Universe viewpoint, shattering wasn't a possibility. The craters were excised from the surfaces by an interplanetary-size electric arc--a "thunderbolt." Instead of exerting a shattering force into the moon, as an impact would do, an arc would dissociate the surface material and lift the debris into space along the current channel.

At the edges of the arc, the electric force would fall off rapidly, resulting in the steep sides of the craters and the "pinched up" rims, contrary to the "heaved out" rims expected from an impact. Furthermore, a thunderbolt would consist of two or more filaments rotating around a central axis. They would cut the surface down to a uniform depth, producing a floor parallel to the surface--which, in the case of Odysseus, means that it reflects the moon's curvature. (This property of uniform depth of excavation is exploited in the industrial use of arc machining.) An impact, of course, would "dig a hole" of varying depth because the impact forces would decrease radially instead of being constant over an area.

Finally, if the individual filaments composing a thunderbolt are sufficiently far from the axis, they will not excavate the material directly under the axis. They will leave a central spire of (relatively) undisturbed material: the central peak. This could be a crucial test to distinguish electrical from mechanical origins. A lander could examine the central peak and determine if it is a pile of rubble that has rebounded from a mechanical impact or if it is a native structure retaining the same features as the surface beyond.


David Talbott, Wallace Thornhill
Amy Acheson
  CONTRIBUTING EDITORS: Mel Acheson, Michael Armstrong, Dwardu Cardona,
Ev Cochrane,   Walter Radtke, C.J. Ransom, Don Scott, Rens van der Sluijs, Ian Tresman
  WEBMASTER: Michael Armstrong

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