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Saturn's moons younger than the dinosaurs, new research says

Earth's dinosaurs first appeared in the Triassic period, 231.4 million years ago.
By Brooks Hays   |   March 24, 2016 at 8:34 PM
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MOUNTAIN VIEW, Calif., March 24 (UPI) -- Some of Saturn's moons are surprisingly young. New research from the SETI Institute suggests some of the gas giant's moons and portions of its rings were formed after the reign of the dinosaurs, just 100 million years ago.

Tidal interactions -- the push and pull of gravitational forces -- between Saturn's inner satellites and the gas giant's inner liquid have altered Saturn's moons and rings over time, pulling them farther out or tilting them at an angle.

Gravitational interactions between moons can also precipitate orbital shifts and tilts. Occasionally, these moons enter into orbital resonances, whereby the two satellites become locked into closely related orbits -- both pulled or titled from their original orbits by corresponding fractions.

Researchers at SETI built a model to simulate the changes in the orbits of Saturn's moons and rings over time. When they looked at the orbits of some of Saturn's inner moons and rings -- including Tethys, Dione and Rhea -- they found more modest alterations than they expected.

The discrepancy suggests some of Saturn's satellites have had fewer tidal forces and gravitational interactions exacted upon them -- fewer opportunities to enter into orbital resonance. Scientists hypothesized that some of these moons and rings haven't been around as long.

In conjunction with their model, researchers estimated the strength of Saturn's tidal forces using data on the moon Enceladus' geothermal activity. The icy moon's consistent and considerable geothermal activity suggests Saturn's tidal forces are quite strong.

Given the power of Saturn's tidal forces and the minimal alterations of Saturn's inner moons, researchers estimated that the gas giant's inner satellites are not more than 100 million years old.

Earth's dinosaurs first appeared in the Triassic period, 231.4 million years ago.

"So the question arises, what caused the recent birth of the inner moons?" asked Matija Cuk, principal investigator at the SETI Institute.

"Our best guess is that Saturn had a similar collection of moons before, but their orbits were disturbed by a special kind of orbital resonance involving Saturn's motion around the Sun," Cuk said in a news release. "Eventually, the orbits of neighboring moons crossed, and these objects collided. From this rubble, the present set of moons and rings formed."

The research is set to be published in the Astrophysical Journal.

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