London: In what is billed as the best ever close-up view of a celestial object, a NASA spacecraft has passed within 700km of a comet taking its pictures in unprecedented detail.
Speeding at eight miles per second, the Deep Impact probe came to within 435 miles of comet called Hartley 2 -- a dirty snowball of rock and ice. Its two ends appeared packed with boulders from which brilliant fountains spewed.
The comet has been named after British-born astronomer Malcolm Hartley, who first spotted it as a faint smudge on a photo while working at Siding Spring Observatory in New South Wales, Australia.
Hartley was at NASA`s Jet Propulsion Laboratory in California yesterday to witness live the flyby which was arried out under a mission called Epoxi.
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 Telegraph reported.
The encounter happened 23 million miles from Earth just weeks after Hartley 2 became one of the closest comets in centuries.
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 travelled 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.
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.
After Tempel 1, the spacecraft 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 the latest 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.
About half an hour after closest approach, the spacecraft began transmitting its spectacular close-ups, a process that lasted several hours.
PTI
