Image of Saturn taken by the robot Cassini. Photo Credits: HO / AFP
According to an American researcher, they would come from leftover an old satellite as big as Titan.
Since their discovery in 1655 by Dutch astronomer Christiaan Huygens, Saturn's rings remain a mystery. Impossible to understand how and when these gems were formed in the solar system, composed of billions of ice less than one meter in diameter. Or why they contain as much water (between 90 and 95%) and so little of silicates, ie rocks and minerals, while the ratio is about 50/50 in most celestial objects in the outer system Sun.
But an American researcher, Robin C'anupa, Southwest Research Institute in Boulder, Colorado, might well have solved the mystery. The "recipe" that he proposes in the British journal Nature suggests that the famous rings are the residue of an ancient "moon" as big as Titan, which would have disintegrated under the influence of powerful tidal forces from Saturn.
"C'anupa model offers, for the first time, the starting point of a convincing theory of the origin of Saturn's rings," write in a comment attached, two French astronomers Crida Aurelian (University of Nice -CNRS) and Sebastien Charnoz, based at CEA Saclay (Essonne).
Hitherto scientists thought that the rings were caused by the impact of a comet on a small satellite of Saturn impacted. Problem: "With this scenario, the rings should be made of a mixture of rock and ice, but this is not what we see today," said Robin C'anupa.
Based on previous work which suggest that Saturn had, in its infancy, several large satellites the size of Titan (5150 km in diameter, more than the planet Mercury), but eventually absorb those orbiting in close proximity, researchers from Colorado has shown, using simulations digital, that one of these "companions" planets could be the "father" of the rings.
Under the effect of the attraction of Saturn, the mantle of ice that surrounds the satellite would have been presumed literally "peeled" and cut to pieces by tidal forces, the same ones that underlie the action of Moon on our oceans but land (fortunately for us) in much less strong.
The rocky core of the satellite, remained intact, would then continued its course toward Saturn, leaving behind him, before disappearing, a myriad of ice which gave rise to the rings and small satellites that revolve still frozen in the vicinity of Saturn, as Tethys, Pan and Atlas.
The U.S. probe Cassini, which orbits the past six years and a half around the second largest planet in the solar system behind Jupiter, would soon be measured very precisely the mass of the rings and indirectly infer their degree of "pollution", c that is to say, the rate of cosmic dust that coalesced over time. Astronomers hope to be able to estimate the age of these structures of fascinating beauty.
http://www.lefigaro.fr/sciences/2010/12/21/01008-20101221ARTFIG00610-l-origine-des-anneaux-de-saturne-enfin-devoilee.php
Marc Mennessier
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