Thursday, July 1, 1999 Published at 15:42 GMT 16:42 UK
Rosetta's epic ride
Eight-year mission to catch comet
The European Space Agency (Esa) has unveiled details of its Rosetta Comet Chaser.
The £650m mission to Wirtanen will last eight years and cover a distance of 5.3 billion kilometres. The space craft will use the gravity of Earth and Mars to shoot itself out into the outer Solar System until it is travelling at the same velocity as the comet, around 130,000 kilometres per hour.
As the comet nucleus evaporates, 12 experiments will map its surface and study the dust and gas particles it ejects. Scientists are very keen to see the results. Comets are among the most primitive objects in the Solar System.
Virtually unchanged after 4.6 billion years in the deep freeze of space, they contain unaltered dust and ice left over from the time the planets were formed. Some scientists even think comets contain simple organic compounds that could have been responsible for seeding life on Earth.
Clues to life on Earth
"The really key question is what role did comets play in the evolution of life."
The UK has instruments on both the orbiter and lander. It is also contributing to a study of the physical properties of the comet's surface, inner structure and tail.
Professor Ian Halliday, chief executive of the Particle Physics and Astronomy Research Council, said: "This is a tremendously exciting mission with extremely demanding technical and scientific requirements, and reflects the key role UK scientists are making to ESA's science programme."