The main purpose of the Rosetta probe and its lander Philae is to study comet 67 P/Churyumov-Gerasimenko.
Launched on 2 March 2004, Rosetta has been through a complex phase of 4 successive gravity assists to reach the speed required to journey to 67 P/Churyumov-Gerasimenko. On the way it flew by the asteroids Steins (5 September 2008) and Lutecia (10 July 2010). It is now in hibernation until 10h00 GMT on 20 January 2014. Hibernation allows precious energy to be saved.
In May 2014 the probe will begin a complex manoeuvre to approach the comet. After determining a landing spot, the lander Philae will set down on the surface of the comet in November 2014 with three methods to ensure that it does not "bounce off" and be lost forever in space. The gravity on a body as small as a comet is extremely weak and not much is needed to permanently escape its gravitational attraction.
The comet will be studied for a period of a year and a half as it approaches the Sun.
Planets and comets have a common origin, they are supposed to have been formed at about the same time in more or less the same way. The current comets were formed further away and have moved further from the centre of the system, attracted by distant stars. Only they return regularly, free of all external influences, and therein lies their interest! Because it is far from the Sun, the comet travels in a very cold universe which slows down its chemical evolution; comets therefore have a 4.5 billion year old memory, and reading it will almost certainly provide the answers to many questions.
Beyond an understanding of the origin of our solar system, Rosetta may bring answers to questions on the origin of life. For comets are partly composed of organic molecules which make up amino acids, elements that are essential to the development of life. Comets may therefore have played a fundamental role by bringing precious "seeds" to earth. It is up to Rosetta to tell us!
The Rosetta probe