Nasa spacecraft comes within 435 miles of comet

Comet got its name,when it was first spotted as a faint smudge on a photo by British-born astronomer Malcolm Hartley, working at Siding Spring Observatory in New South Wales, Australia.

Mr Hartley, 63, flew to Nasa's Jet Propulsion Laboratory in California to witness the flyby live.

Scientists are excited about the close-up pictures and other data because the comet is made up of material from the edge of the solar system little changed over four billion years.

The encounter happened 23 million miles from Earth just weeks after Hartley 2 became one of the closest comets in centuries.

Deep Impact, which is unmanned and the size of a small car, previously visited another comet, called Tempel 1, on July 4, 2005, when it fired a missile that caused a brilliant explosion and blasted out a crater.

Its mission was renamed Epoxi. Project manager Tim Larson, of NASA's JPL, said: "The mission team and scientists have worked hard for this day. It's good to see Hartley 2 up close."

EPOXI principal investigator Michael A'Hearn, of the University of Maryland, said: "We are all holding our breath to see what discoveries await us in the observations near closest approach."

The geyser-like eruptions from Comet Hartley 2's icy heart were due to warming by sunlight after it tracelled in from deep space. A green atmospheric shell of gas, including poisonous cyanide, has developed and a tail of dust ejected.

The comet, which came as close as 11 million miles last month, takes six and a half years to orbit the sun. It has been visible to amateur astronomers through binoculars or even with the unaided eye as a fuzzy glow in clear dark skies but is now fading as it passes through the constellation of Gemini.

After Tempel 1, Deep Impact was supposed to visit another comet called Boethin but when NASA looked for it they found it had disappeared, and probably broken up.

During the early stages of yesterday's encounter, all of the close-up images were stored onboard the spacecraft. This was because Deep Impact cannot simultaneously point its high gain antenna toward Earth and its imagers toward the comet.

(source:telegraph.co.uk)