In March 1986, ESA's Giotto spacecraft flew to within 600 km of comet Halley's nucleus. It sent back the first close-up pictures of a comet's icy heart. Now, another ESA spacecraft, named Rosetta, is on its way to a comet. Rosetta is the most complex space mission ever flown by Europe.
The 3 tonne spacecraft carries 11 experiments and a lander, which has another 9 experiments. It gets its power from two huge solar panels, each 14 metres long.
Launched on 2 March 2004, Rosetta will take 10 years to reach comet Churyumov-Gerasimenko. The roundabout route includes three flybys of Earth and one of Mars. Rosetta also dips in and out of the main asteroid belt between Mars and Jupiter. This enables it to take close-up images of two asteroids, Steins and Lutetia.
On arrival near the comet, Rosetta will slow down and change its path so that it enters orbit only a few kilometres above the solid nucleus.
Once the comet has been mapped, Rosetta will release its lander (called Philae). This will anchor itself to the nucleus and send back the first pictures from a comet's surface.
Up above, the orbiter will follow the comet as it speeds toward the inner Solar System. During this 18-month chase, the comet's frozen ices will turn to gas, sending jets of material shooting into space. Rosetta will show us for the first time the dramatic changes that take place as this iceberg in space is warmed by the Sun.