Rosetta will allow scientists to look back 4600 million years to an epoch when no planets existed 

and only a vast swarm of asteroids and comets surrounded the Sun


ESA's Rosetta spacecraft

 will unlock the mysteries of the oldest building blocks of our Solar System – the comets

What are the mission’s objectives

Rosetta's prime objective is to help understand the origin and evolution of the Solar System. The comet’s composition reflects the composition of the pre-solar nebula out of which the Sun and the planets of the Solar System formed, more than 4.6 billion years ago



What makes the Rosetta mission so special?
Rosetta will be undertaking several ‘firsts’ in space exploration. It will be the first mission to orbit and land on a comet. That makes Rosetta one of the most complex and ambitious missions ever undertaken. Scientists had to plan in advance, in the greatest possible detail, a ten year trip through the Solar System. Approaching, orbiting, and landing on a comet require delicate and spectacular manoeuvres. The comet, 67P/Churyumov-Gerasimenko, is a relatively small object, about 4 kilometres in diameter, moving at a speed as great as 135,000 kilometres per hour. We know very little about its actual surface properties – only when we get there will we be able to explore the surface in such detail that we can choose a safe landing scenario. Rosetta is very special because of the unique science it will perform. No other previous mission has had Rosetta’s potential to look back to the infant Solar System and investigate the role comets may have played in the beginnings of life on EartWhat makes the Rosetta mission so special?

Rosetta will be undertaking several ‘firsts’ in space exploration. It will be the first mission to orbit and land on a comet. That makes Rosetta one of the most complex and ambitious missions ever undertaken. Scientists had to plan in advance, in the greatest possible detail, a ten year trip through the Solar System. Approaching, orbiting, and landing on a comet require delicate and spectacular manoeuvres. The comet, 67P/Churyumov-Gerasimenko, is a relatively small object, about 4 kilometres in diameter, moving at a speed as great as 135,000 kilometres per hour. We know very little about its actual surface properties – only when we get there will we be able to explore the surface in such detail that we can choose a safe landing scenario. Rosetta is very special because of the unique science it will perform. No other previous mission has had Rosetta’s potential to look back to the infant Solar System and investigate the role comets may have played in the beginnings of life on Earth



How did Rosetta reach comet 67P/Churyumov-Gerasimenko, and how long did it take
Comet 67P/Churyumov-Gerasimenko loops around the Sun between the orbits of Jupiter and Earth, that is, between about 800 million and 186 million kilometres from the Sun. But rendezvousing with the comet required travelling a cumulative distance of over 6.4 billion kilometres. As no launcher was capable of directly injecting Rosetta into such an orbit, gravity assists were needed from four planetary flybys – one of Mars (2007) and three of Earth (2005, 2007 and 2009) – a long circuitous trip that took ten years to complete.

Why is it so important to study comets?
Comets are of great interest to scientists because, to our knowledge, they are the oldest, most primitive bodies in the Solar System, preserving the earliest record of material from the nebula out of which our Sun and planets were formed. Planets have gone through chemical transformations, but comets have remained almost unchanged. Furthermore, comets brought ‘volatile’ light elements to the planets and likely played an important role in forming oceans and atmospheres. Comets also carry complex organic molecules that may have been involved in the origin of life on Earth.

What do we presently know about how the Solar System formed?
The Solar System formed about 5 billion years ago when a cloud of gas and dust – called the ‘pre-solar nebula’ – started to collapse due to gravitational forces. A disc of leftover material made of the same gas and dust present in the primordial cloud formed around the still-forming Sun. After the Sun ‘ignited’ and began its life as star, most of the particles in this disc collided and stuck to one another, growing in size until they became the planets and the other Solar System bodies.

However, it took some time before the Solar System became the way it is now. About 4.5 billion years ago, it was still 'under construction', and interplanetary space was littered with conglomerates of dust particles. Many of these chunks hit the planets and were destroyed in the collision, but thousands of millions of them survived – they are the asteroids and comets we know today.