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 A previously unknown ring of Saturn was revealed recently by the Cassini spacecraft last Sunday, as it spent over entire Saturnian day in the planet's umbra, or nightside shadow. Backlighting from the sun revealed this latest ring. Scientists' best guess indicate that it is made from dust resulting from meteoroids colliding with two moons that orbit at the same distance.
The moons in question, Janus and Epimetheus, are too small - a mere 120 and 85 miles across (194 and 138 km) - for the type of volcanic activity capable of spewing volcanic dust into space like Enceladus, which is nearly three times the size of the larger moon, Janus. "When an object is that small, it's basically a dead ice ball," said Mark Showalter of California's SETI Institute. "There really can't be much going on except the shooting gallery out there of meteoroids and little comets."
Because these two moons are so small, they are incapable of holding on to dust stirred up by meteor impacts. The dust escapes into outer space, where it is captured by Saturn's gravity and eventually forms a ring. While other planetary rings may be formed this way - similar rings exists in the orbit of Saturnian moon Atlas, as well as the orbits of Jovian moons Thebe and Amalthea and Uranian moon Mab - it begs the question of why other tiny moonlets like this do not have similar rings.
Cassini measured the rings with its Infrared Spectrometer. The data should eventually tell scientists the speed of the ring's particles, its rate of rotation and how often they collide. In the meantime, click on the thumbnail above for a more detailed look at the newest addition to Saturn's family of rings.
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