Doomed Moons 
One of the basic goals of the “green” movement is to get people to recycle. For inspiration, we might look to a green planet, which seems to be recycling entire moons.
Uranus is the third-largest planet in the solar system. Methane in its upper atmosphere gives it a greenish color. The planet is putting in its best showing of the year right now; through binoculars, it looks like a tiny star in the constellation Pisces. More about that tomorrow.
Uranus is circled by 27 known moons. But some of them won’t last long. They’ll eventually slam together, pulverizing the moons and encircling Uranus with fresh, bright rings.
Researchers at the SETI Institute modeled the orbits of the 13 moons that are closest to Uranus, which are packed close together. In dozens of simulations, the researchers found that three of the moons are doomed to destruction in the next couple of million years: Cupid, Cressida, and Belinda.
The fact that the system is so unstable means the moons can’t have been in those orbits for long. Some of them could be chunks of a larger moon that was destroyed in an earlier impact. Or they could have formed as clouds of debris from one or more impacts clumped together to make larger bodies.
And it’s possible that if the moons are destroyed in the future, some of their debris could coalesce to form more moons. It’s a recycling project that might have been going on for a long time — and could continue far into the future.
Script by Damond Benningfield, Copyright 2011