World holds its breath as space probe prepares to crash-land

Results of 12-year mission depend on photos as Rosetta smashes into comet

A HISTORIC mission by European space probe Rosetta to gather data on a comet has cost £1billion and taken 12 years – but its success all hinges on the scientists behind it getting the perfect picture this Friday.

The team faced an agonising choice of whether to deliberately crash into comet 67P/C-G, giving them just one shot, or to make a slow descent, allowing many photo opportunities but risking spoiling the findings by disturbing more space dust, which would make navigation tricky.

For weeks, the brightest minds at the European Space Agency (ESA) were locked in debate over what to do.

Eventually they decided: at 11.40am BST on Friday, Rosetta will smash head-first into the comet.

It was thought using arrester rockets to slow Rosetta down could buy an extra 45 minutes of photography and analysis, but mission control feared it would taint the atmosphere with dust, making pictures fuzzy.

The debate was won by the purists, who argued in favour of photographs of an unprecedentedly pure quality, albeit fewer of them.

Rosetta, which launched in 2004, will now career unarrested towards its rocky grave, taking its final picture of crystal-clear quality just 15 metres (49ft) above the asteroid.

The risk is that the craft will not have time to “downlink” its data back to Earth.

“It took some time to decide what the best solution would be, but in the end we decided that what really mattered to us was the purity of the science,” said Dr Patrick Martin, mission manager at ESA, based in Darmstadt, Germany.

“It’s about getting the highest-resolution images. That’s going to be really challenging in terms of the downlink, but we are after a unique scientific return.”

Rosetta has been orbiting the comet since August 2014, taking readings and acting as a mothership to detachable probe Philae, which made a bumpy landing on 67P/C-G three months later.

The value of the mission is what the data reveals about comets’ origins.

“If you put everything together, it points to the fact that this comet, and probably many others like it, have been around since the very early solar system,” said Dr Martin. He said the next step would be to design a spacecraft to land on a comet and bring samples back to Earth.