Meteors are also objects of fascination for purely scientific reasons. Most of the particles which produce meteors have been ejected by comets passing through the inner Solar System. Since comets are thought to be left-overs from the formation of the planets, studies of meteors allow scientists to learn more about the physical and chemical characteristics of their 4.5 billion year-old parents.

Figure 6. The Halley comet nucleus imaged by Giotto during its flyby

However, there are limits to such ground-based observations. The only way to study comets at first hand is to send a spacecraft to study them at close quarters. ESA's Giotto spacecraft paved the way with the first close flyby of a comet (Halley) in 1986.

An even more ambitious and exciting project has been planned by ESA - the Rosetta mission to Comet Churyumov-Gerasimenko. Launched in 2004, Rosetta will spend eight years circling the Sun before it closes in on Churyumov-Gerasimenko's icy nucleus. After entering orbit around the comet, it is planned to drop a small lander onto the comet's black nucleus to provide information on its composition, temperature and density.

Over the next two years, the mother spacecraft would orbit just one kilometre above the nucleus, monitoring the changes which take place as it heads towards the Sun and starts to vapourise. If the spacecraft survives its long trek through space and its buffeting from gas and dust jets spurting from the nucleus, it will make the first detailed record of the transformation that takes place when a comet switches from frozen inactivity to boiling effervescence.

Meteors, comets and space missions