October 7, 2010

Moon Collision Possibly Responsible For Saturn’s Rings

The rings of Saturn could have formed after a moon the size of Titan crashed into the developing planet, a researcher from the Southwest Research Institute (SWRI) in Boulder suggested earlier this week.

Speaking during a meeting of the American Astronomical Society's Division for Planetary Science in Pasadena, California, SWRI researcher Robin Canup suggested that the satellite likely had a mantle made of ice and a rocky core, and that tidal forces might have dislodged chunks of the mantle prior to the actual impact, BBC News Science Reporter Katia Moskvitch reported on Wednesday.

According to Moskvitch, Canup's theory could explain why the rings are comprised of between 90% and 95% water and ice, with only trace amounts of rock that the SWRI scientist says could have come from interplanetary dust and micro-meteoroid bombardment. The composition of Saturn's rings is odd because the primordial solar system would have been about equal parts rock and ice, according to Richard Lovett of Nature News.

"Prior theories suggested that the rings were produced by the breakup of a small moon that fell too far into Saturn's mammoth gravity or by the breakup of a very large comet that suffered the same fate," Lovett wrote on Tuesday. "But the small-moon theory begs the question of why there is so little rock. And comet disruptions should have been much more common at Saturn than at other outer planets," he said Canup noted in her presentation's abstract.

Because of the composition of the planet, Canup said that the ice from the mantle would have broken off and been distributed into what would eventually become Saturn's rings. However, the thicker, rocky core would not have disrupted before impact, meaning that none of the rock would have been pulled into the forming rings. After the impact, some of the ice also eventually formed into new moons, and the rings themselves began forming the interstellar dust to reach their current composition.

"It is a very clever new idea," Cornell University planetary scientist Joseph Burns told Lovett. "One of the things it can do is produce rings made out of quite pure water ice, which has been a problem in the past"¦ She has a pretty convincing story, I would say."

The rings of the planets will be further studied as part of the Cassini Equinox Mission, which entered Saturn's orbit in July of 2004. Cassini is the fourth space probe to visit Saturn, but the first to enter the planet's orbit. Its mission currently set to continue until September 2017.


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