Wendy Hillman, age 12, of Fredericton, New Brunswick, Canada, for her question:

Why is Saturn the only planet with rings?

Astronomers suspect that Saturn's rings may be the result of a very rare kind of accident. Once in an astronomical age, an orbiting moon may veer too close to its parent planet. It is thought that forces of gravity would cause tidal upheavals strong enough to shatter such a moon to fragments. It seems logical to suppose that the debris would continue to orbit around the planet in dusty circles lit by golden sunshine.

If this theory is correct, it is astonishing that such a rare accident occurred even once in our Solar System. It has been proved that the planets and their moons move around in very stable orbits, at least for the present. We are not likely to get another ringed planet in the near future. However, it has been predicted that in the far future, our moon may move too close for safety. Several billion years from now, the earth's moon may become a series of circling rings.

Recent information from various planetary spacecraft has enabled us to observe a ring around  Jupiter and faint rings around Uranus and Neptune.  We still do not have the answer to the question of what causes rings to form around certain planets.