Comet the hour, comet the man

This week speeding spacecraft Rosetta will try to send down a probe to land on and study the comet it has been chasing across the solar system for a decade.

Rosetta has been manoeuvred into position at high speed and is now close enough for its tricky task, say scientists.

On Wednesday, it will launch the landing craft Philae, bound for the comet's icy surface.

Scientists at the European Space Agency will face a nerve-jangling final few hours as they wait to find out whether their years of patience and calculations have resulted in a successful touchdown.

If the spacecraft is misaligned by just 1cm upon launch, the probe could drift hundreds of metres off target.

The team has until 8pm on Tuesday evening to decide if conditions are stable enough to go ahead.

If successful, it is hoped that the probe will provide data that could reveal the origins of life on Earth.

Made of ice, dust and small rocky particles, it is likely that comets delivered the first water to Earth and may have even seeded the planet with the building blocks for life.