Europeans to land on a comet

European space scientists are counting down to the launch of Rosetta, the mission to put a lander on a comet. The Ј600m, 12-year space expedition is scheduled to launch from French Guiana's Kourou spaceport on 26 February aboard an Ariane-5 G+ rocket. But the high-risk mission will need to overcome major technical challenges.

"Rosetta will be the first ever spacecraft to perform a soft landing on a comet's nucleus," UK science minister Lord Sainsbury told a news conference. "This will allow Rosetta to carry out more in-depth study (of a comet) than has ever been done before."

The Rosetta spacecraft will despatch a lander, named Philae, to touch down on the icy nucleus of the comet Churyumov-Gerasimenko. The mission continues a long association between the European Space Agency (Esa) and comet exploration that was cemented when the Giotto probe obtained close-up images of Comet Halley's nucleus in 1986.

"Rosetta will have been ten years and several hundreds of millions of miles and then have to land on something like that - it's an audacious mission," said mission scientist Dr Ian Wright of the Open University. The launch will go ahead despite the last minute detection of mechanical problems in January, informs &to=http://www.bbc.co.uk' target=_blank>BBC

Rosetta will be the first spacecraft to go into orbit around a comet's nucleus. It will be the first to ride alongside a comet as it loops around the sun. It will be the first to see how a modest lump of ice and dust from the outer suburbs of the solar system transforms into a spectral vision with a glowing tail.

It will make the first soft landing on a comet, and it will provide the first chance to directly analyse the stuff of a comet.

It will be the first spacecraft to get as far as Jupiter using solar panels to generate power. And it will have the first close encounter with one of the mysterious lumps of rock in the asteroid belt between Mars and Jupiter.

Rosetta gets its name from the Rosetta stone, now on display in the British Museum, which offered the first key to deciphering Egyptian hieroglyphics. Philae is named after an obelisk found in the upper Nile that provided another powerful clue: it carried the cartouches of Cleopatra and Ptolemy. The technical challenges have been huge. More than half the mass of the three-tonne spacecraft will be fuel to allow it to complete its mission.

It needs instruments and communication systems able to survive 12 years in a climate that falls to minus 150 C (minus 235F) beyond Jupiter but rises to the heat of a Provençal summer nearer the sun.

When the encounter begins, light - and therefore radio commands - will take almost an hour to reach the spaceship, so it has had to be designed to be able to think for itself as well as respond to its controllers.

The lander will have to touch down on a comet with a texture that could be as hard as concrete or as yielding as candyfloss, with a gravitational tug 10,000 times weaker than Earth's, so it will have to be attached with a harpoon to stop itself bouncing off again, according to &to=http://www.guardian.co.uk' target=_blank>Guardian