Europe’s comet explorers
3 December 2012
On 13 March 1986, ESA’s Giotto spacecraft sent back pictures of a black, potato-shaped object that was blasting bright jets of material into space. It was the first time that anyone had seen the solid nucleus at the heart of a comet.
Giotto’s target was Comet Halley, named after the 17th century British astronomer, Edmond Halley. He was the first person to realise that this bright comet is a regular visitor, returning to the inner Solar System every 75–76 years. Its next visit to our skies is scheduled for 2061.
Halley’s comet is the most famous of the millions of comets that travel around the Sun. Even when it is in the darkness of the outer Solar System, Halley still affects our planet. Every October, Earth passes through a stream of fine dust left behind by the comet, causing the Orionid meteor shower. Halley’s comet is also thought to be responsible for the Eta Aquarid meteor shower, which occurs every year in May. These meteors, often known as “shooting stars”, are bright trails left by tiny, fast-moving grains of comet debris which burn up in Earth’s atmosphere.
Since Giotto’s remarkable success, other comets have been studied by spacecraft. However, the most ambitious mission is ESA’s Rosetta comet-chasing spacecraft, which will arrive at Comet Churyumov-Gerasimenko in 2014. Rosetta will fly alongside the nucleus, making an in-depth study of the changes that take place as it is warmed by the Sun. It will also release a small craft called Philae, to carry out the first soft landing on a comet!