The Rosetta space odyssey

On 2 March 2004 a European spacecraft that will chase down a comet in search of clues to the origin of life on Earth lifted off from the Kourou spaceport in French Guiana. An Ariane‑5 rocket carrying a European Space Agency probe set course for the comet Churyumov‑Gerasimenko.

The Rosetta probe will take 12 years to catch the comet Churyumov‑Gerasimenko. When it does it will become the first spacecraft to make a soft, controlled landing on the nucleus of one of the solar system’s enigmatic icy wanderers.

The mission aims to unlock the secrets of the solar system’s beginnings 4.6 billion years ago, of which comets are largely unchanged relics, containing the same materials from which the planets were formed.

It will answer important questions about what the “dirty snowballs” are made of, and even whether comets could have “seeded” Earth with the water and organic chemicals required for the genesis of life.

Rosetta will use three Earth fly‑bys and another of Mars as a “gravity slingshot” to catapult it towards Churyumov‑Gerasimenko, which has a core about the size of Heathrow Airport.

On completing its 7 billon‑mile journey in 2014, Rosetta will orbit the comet’s nucleus and drop a lander named Philae, the size of a washing machine, on to its surface.

The mother ship takes its name from the Rosetta Stone which was discovered in Egypt in 1799 and provided the first key to deciphering hieroglyphics. Scientists hope the data it gathers will offer equally critical insights to the origins of the solar system and terrestrial life. Its Philae lander is named after an island in the Nile where an obelisk critical to the understanding of the Rosetta Stone was found.

The probe was delayed several times because of problems with the Ariane‑5 rocket and had originally been scheduled to visit a different comet, named Wirtanen. The European Space Agency changed its target when the Wirtanen launch window was missed early in 2003.

Britain has contributed £70 million towards the probe’s £600 million cost, and it was partially built by the Stevenage‑based satellite company EADS‑Astrium. British scientists have also contributed to 11 of the 21 instruments it will fly.

Professor Ian Halliday, chief executive of the Partide Physics and Astronomy Research Council, said:

“This mission will turn science fiction into science fact. Every aspect of comet Churyumov‑Gerasimenko will be analysed, resulting in the most comprehensive set of scientific measurements ever obtained of a comet and the UK can be justly proud of the significant part it has played. This ground‑breaking mission benefits from considerable involvement by talented scientists from UK universities.”

Lord Sainsbury of Turville, the Science Minister, said:

“It is hoped the Rosetta mission will provide us with an understanding of the origins of the Sun and the planets, including Earth. It could provide answers to how life actually began.”

Rosetta will start orbiting the comet in May 2014. Once it has identified a landing site, it will release Philae, which will hit the ground at walking speed.

Philae will drill into the comet’s core to take samples, and take close‑up pictures, thus becoming the first probe to make a controlled landing on a comet. A NASA spacecraft to be launched in December, named Deep Impact, will crash into a comet in 2005, but will be destroyed in the process.

Both the European lander and orbiter will operate for more than a year, collecting information on the comet’s composition, and on the way in which its icy core starts to melt as it approaches the sun.

One British‑led experiment, named Ptolemy, will analyse the chemical composition of samples from the comet’s core. If these match those found on Earth, it would be possible that water and organic materials first reached Earth on comets.

Ian Wright of the Open University, principal investigator for Ptolemy, said:

“The study of these biologically important elements is strongly implicated in our quest to understand the origin of life on Earth.”