Why has Saturn got rings while the other planets in our solar system don t

A. Saturn was considered unique because of its famous rings up until 1977, when it was discovered that Uranus, Jupiter and Neptune all have faint rings also.

Q. Where did Saturn's rings come from

A. While scientists acknowledge that they know relatively little about Saturn's rings it's thought that the rings were formed from the debris of an object that passed too close to the planet and broke up.

As to where the unfortunate object came from, the latest findings from the Hubble Space telescope suggest that its origins are the distant outer Solar System.

Q. How do scientists know where the object whose debris forms Saturn's rings came from

A. Because of their colour. The rings aren't white, but a faint pink colour, hinting that they're composed of a mixture of complex organic molecules and ice. Scientists had suggested that the object that broke up and whose debris now forms the rings was a moon.

However Saturn's seven small icy moons are not pink in colour, but many icy objects in the distant, frozen outer reaches of the outer Solar System are.

Q. What are Saturn's rings made of

A. Mainly small chunks of dispersed rock and ice. The latest research suggests that there may also be at least to other unknown materials making up the rings. The way these materials are distributed is unlike anything known from other planets or their moons.

Q. How big are Saturn's rings

A. They are 270,000 km in diameter, but only a few hundred meters thick. The particles that make up the rings are tiny: measured in centimetres.

There are four main ring groups and three more faint, narrow ring groups separated by gaps called divisions.

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by Lisa Cardy