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Moon and Saturn

April 7, 2015

The rings of Saturn are among the most beautiful objects in the solar system — and perhaps among the most ephemeral as well. They may undergo dramatic changes, with old rings disappearing and new rings forming over millions of years.

Saturn's moon Pan moves through the Encke GapPan, a small moon of Saturn, moves through the Encke Gap, which is outside the A ring, in this Cassini view [NASA/JPL]The main set of rings spans about two-thirds of the distance from Earth to the Moon. The rings are named with the letters A through D. The D ring is closest to Saturn, beginning just a few thousand miles above the planet’s cloudtops. And the A ring is farthest, with its outer edge almost 50,000 miles out.

Each of these rings actually consists of hundreds of smaller rings. They’re made of various mixtures of ice, rock, and dust, so each major set of rings looks different from the others.

That may be because they were born from different parent bodies. The rings likely are the remains of one or more moons that were pulverized by collisions with other bodies, or by the tug of Saturn’s gravity. The debris from such collisions grinds together, creating smaller and smaller pieces.

But some debris may eventually coalesce to form a new moon, which may then be blasted apart in another collision. This process may have repeated itself over the eons many times — giving Saturn a succession of moons and rings.

And Saturn is in good view tonight. It’s just below the Moon as they climb into view after midnight, and looks like a bright star. The bright true star Antares is not far below Saturn, and we’ll have more about that tomorrow.


Script by Damond Benningfield, Copyright 2015

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