Mysterious visitors
Comets have puzzled people for centuries. These visitors from the outer reaches of our Solar System are frozen pieces of debris, which travel in elliptical orbits, like a long oval, and develop long tails as they approach the Sun.
Because comets have hardly changed since the birth of the Sun, scientists hope they'll provide clues about the earliest history of our Solar System. The Rosetta and Stardust missions are on the trail.
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| Mysterious icy travellers |
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