Rosetta heads to its death with comet crash

Europe's most ambitious space mission will come to an end within hours as Rosetta is ordered to crash into the comet it has been circling for the last two years.

Controllers at the European Space Agency are putting the spacecraft on a collision course with comet 67P.

It will descend at walking pace from an altitude of 12 miles (19km) towards the 'head' of the duck-shaped comet.

Rosetta will continue to sample gas and dust as it free-falls, and take a series of images of the surface.

Its final task will be to close in on one of the many pits that pockmark the comet. They are up to 425ft (130m) wide and 200ft (60m) deep and eject jets of gas and dust.

Scientists are intrigued by 'goosebumps' or 'dragon's eggs', one-metre lumps that line the pits and are thought to be the comet's building blocks when it formed 4.6 billion years ago.

Matt Taylor, one of the ESA scientists analysing the huge amounts of data sent back to Earth, said: "It's pleasing for me to see how the results are being put into context to how the solar system evolved.

"It is fantastic to have this data set and it has fantastic implications.

"Because there is so much data and it is so good there will be decades of work from it."

Impact is expected at around 12.20pm UK time, with confirmation expected 40 minutes later as the signal from the spacecraft disappears from instruments at mission control in Darmstadt in Germany.

::The mission in numbers:
::12 years, six months, 28 days: mission duration, from launch to end
:: 7.9 billion km (4.9 billion miles): distance travelled since 2004
:: 786 days: time Rosetta spent circling the comet
:: 720 million km (450 million miles): current distance from Earth
:: 14 hours: the duration of Rosetta's freefall
:: €1.4bn (£1.2bn): the cost of the mission
:: 500: scientists and engineers involved in the project

Comet 67P is currently 450 million miles (720 million km) from Earth, travelling towards Jupiter at 32,000mph.

The sun's light is now too weak to power the spacecraft for much longer and mission control opted to end the mission with a collision while they could.

The mission has cost about £1.2bn. But it is the first time a spacecraft has orbited and landed on a comet.

It has detected complex forms of carbon not found on Earth, a building block of proteins called glycine, and for the first time phosphorus which is a key component of DNA.

Scientists say the chemical make-up supports the theory that comets smashing into the Earth billions of years ago brought the ingredients for life.

But contrary to expectations, the chemical signature of water on the comet differs to that of our oceans, suggesting comets like 67P did not fill our seas.

Ian Walters was involved in designing the spacecraft at Airbus Defence and Space in Stevenage in 1998.

He told Sky News Rosetta's encounter with the comet had been like "science fiction".

"At the time we were just building a spacecraft," he said.

"That was exciting enough, but now we are there and we can see what a comet looks like, it's thrilling.

"We will be celebrating. It's a tremendous achievement. But also a bit sad because it's the end of a 20-year programme."