But it was only five years since the arrival of the Cassini Mission Saturn high-resolution strange moon Iapetus international global community has thought deeply about the shape of Walnut single large body (735 kilometer radius), regarded by many as one of the most amazing features of the solar system.
And there is no consensus on how a mysterious high ridge which covers more than 75% of the Moon Ecuador was formed. It was difficult to crack a nut.
But now a team comprising a specialist external solar system, of Washington University in St. Louis has proposed a giant impact explains the Ridge up to 20 kilometres high and 100 kilometres wide.
William b. McKinnon, Dr.., Professor at the University of Washington potato and planetary in arts and sciences science and his former student PhD, Dr. Andrew Dombard, Earth and environment at the University of Illinois Chicago (UIC), sciences Professor propose that at a given moment Iapetus himself was a satellite or moon, created by a giant with another big agency impact.
Orbit satellite-sub, they say, would have rotted due to tidal interactions with Iapetus, and he would have gradually migrated to Iapetus. At one point, researchers say, tidal forces would have torn the however, forming a ring of debris around Iapetus which would eventually be snapping in the Moon of the Ecuador.
"Imagine all these particles down horizontally on the Equatorial surface approximately 400 metres per second, the speed of a bullet, one after another, as bullets frozen baseball," explains McKinnon.
"Particle would impact one by one, over and over again on the Equatorial line." First the debris would have made holes into a Groove that finally completed. »
"When you have a ring of a body, interactions collision debris flying energy out of orbit," explains Dombard.
"And that an organization can lower energy State is just above the rotation of a planetary body - the Ecuador bulge. This is why the rings of Jupiter, Saturn, Uranus and Neptune are above the Ecuador. »
"We have many corroborating calculations show that it is a plausible idea," said Dombard, but we do not yet have any tough to show the action process simulations. "I hope it's next".
Other planetary scientists believe that Ridge was created by endogenous (within the planet) activity such as volcanism or the forces of mountain-building.
"Some people have suggested that Ridge could have been caused by a chain of volcanic eruptions, or perhaps a series of faults," notes McKinnon. "But to harmonise all perfectly like - it is just no similar examples in the solar system to point to such a thing."
"There are three critical remarks that any what model for the formation of the Ridge must meet," said Dombard. "They are: why the feature is sitting on the Ecuador.". why only on the Ecuador and why only Iapetus. I think we have something here that explains all these comments. »
Dombard will make a presentation on preliminary findings to the autumn meeting of the American Geophysical Union in San Francisco. The team also included Andrew f. Cheng at the Johns Hopkins Applied Physics Laboratory and Jonathan P. Kay, student at UIC.
Dombard says the Hill sphere of Iapetus - near area of an astronomical body where the gravity of the body dominates satellites - is much more important than any other satellite major solar system external, explains why Iapetus is the only agency recognized as such a ridge.
"Single Iapetus could have the subsatellites orbital space then moving and descend towards the surface break and provide the Ridge," he said.
Support calculations performed team had an estimate for how much time should be orbit disintegration of material likely to reach the point where the tidal forces would tear it into a disc of debris.
"We are trying to just 100,000 years for a still relatively close (for Iapetus) to a billion years to a body which is at the boundary where you have a stable satellite in orbit around Iapetus," explains Dombard.
"These time scales are certainly plausible considering we have billions of years of time to work with." And longevity is important, because if it happens too fast all geological traces will be lost.
Notes are McKinnon has other examples in the solar system of giant impacts, creating some moons that orbit of planets, including our own Moon and pluton Moon Charon.
"Our Moon and pluton, too, are actually decline of Earth and pluton," he said.
"But if we had to bring our moon within what is called geosynchronous altitude, that special altitude where TV broadcast satellites (and other objects) are capable of place a spot on the Earth as they orbit, the moon would be effectively spiral in verse Earth." Finally the moon would break in a ring of particles because she is very narrow and was torn apart by the tides, then these particles would be entering the atmosphere and the Earth to Ecuador bomb. »
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