The mysteries at the heart of the comets may be revealed by a European space probe to be launched early next century.
Scientists hope that the encounter of the spacecraft Rosetta with Wirtanen's comet will provide invaluable clues towards the formation of the solar system and the planets.
The probe, which will be announced at the Royal Astronomical Society meeting in Liverpool this week, will be funded by the European Space Agency, to which Britain contributes. It is hoped the mission will blast off from French Guiana in January 2003 and crash into the nucleus of the comet 10 years later.
Planned cuts in the space agency's funding initially put the voyage in doubt. But the Government's Particle Physics and Astronomy Research Council was able to find money and the mission will now go ahead.
Rosetta will chase the comet for eight years as it approaches the Sun, passing through the bright tail to orbit the solid nucleus. It will send important scientific data to Earth about the development of the comet as it approaches the Sun. Plans to bring back a part of the comet for analysis had to be shelved because of the cost.
Two small probes will be dropped on to the surface of the comet's nucleus, carrying out experiments on samples of the matter making up the comet. The probes will be built by French and German companies and will carry instruments from British universities and laboratories, including Sheffield University, Imperial College, London, and the Mullard Space Science Laboratory near Dorking, Surrey.
Rosetta will be the first craft to land on the surface of a comet. The Giotto probe followed Halley's comet in 1986 but did not land.Reuse content