Its quarry is Comet Wirtanen, a ball of rock and ice just 600 metres across. 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. Once in orbit around the Wirtanen, the probe will release a lander that will touch down on the comet's surface. The lander and probe will monitor the changes taking place on the comet as it hurtles in towards the Sun.
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. The really key question is what role did comets play in the evolution of life. Dr Schwehm used the conference to show off a quarter-size model of Rosetta and its lander.