Comet mission ready for key stage

An space mission to land a device on top of a moving comet will begin a key part of its journey on Friday.

Space experts have designed the mission so that the Rosetta space probe will meet up with a particular comet in deep space in the year 2014.

But to get there the craft needs to be moving very, very quickly and it would take a lot of fuel to move that fast.

Rosetta was launched in 2004, and since then it's been flying around the Earth, the Sun and Mars to build up speed.

Click here to see an animated guide to the Rosetta mission

The mission has been put together by European space scientists, and has cost a billion Euros (£900 million).

When Rosetta gets to the comet, called 67P/Churyumov-Gerasimenko, it will launch a smaller craft called Philae which will try to land on the comet.

13.3km every single second

Scientists want to study comets because they have changed very little in the millions of years since the Solar System was formed.

At the point when Rosetta leaves the Earth's atmosphere it will be travelling 13.3km every single second.