Nasa probe makes deep impact

Nasa's probe collides with Tempel 1

Nasa successfully fired a 372kg probe into Comet Tempel 1 this morning after a trip of 431 million kilometres that took 172 days.

The probe hit the comet at 10 kilometres a second ejecting debris that is being analysed by the Deep Impact spacecraft orbiting the comet.

Scientists hope to use the data to find out more about the origins of the solar system, when most comets were formed. 

"What a way to kick off America's Independence Day," said Deep Impact project manager Rick Grammier of Nasa's Jet Propulsion Laboratory in Pasadena.

"The challenges of this mission, and the teamwork that went into making it a success, should make us all very proud."

The project has a secondary function in terms of analysing the comet's core. Plans to protect the earth in the event of a large object on a collision course require detailed information of comets' structure.

There is no danger that the impact will divert the comet's course. One expert described the probe's effect as similar to "a fly hitting your windscreen on the motorway".

This was an important success for Nasa after a series of problems including the recent loss of the space shuttle Columbia.