A NASA spacecraft flew through the bright halo of a distant comet to scoop up less than a thimbleful dust that could shed light on how our solar system was formed.
NASA said its Stardustspacecraft passed within an estimated 143 miles of the comet Wild 2 yesterday, as it ploughed through the gossamer cloud that cloaks the dirty ball of ice and rock.
Mission members said the unmanned probe made its closest approach while travelling at a relative speed of 13,650 mph.
"We passed the closest approach point without any injury, apparently," said scientist Donald Yeomans, of NASA 's Jet Propulsion Laboratory.
Stardustwas designed to gather hundreds if not thousands of dust particles streaming from Wild 2 during the fly-by 242 million miles from Earth.
The unmanned spacecraft also was due to snap 72 black-and-white close-ups of the comet's nucleus, thought to be just 3.3 miles across.
Mission members warned comet fly-bys are risky, given the violent battering dust particles can give a spacecraft. Engineers gave Stardustarmoured bumpers to shield it during the encounter.
Scientists want to return samples of the particles to Earth for study because they represent pristine examples of the building blocks of our solar system dating back 4.6 billion years. They also believe the dust contains many of the organic molecules necessary for life.
Members of the $200 million mission planned for Stardust to sweep back past the Earth in January 2006 and jettison a canister containing the particles, allowing it to fall to the ground in Utah.
If returned, the particles would represent the second robotic retrieval of extraterrestrial material since 1976, when the unmanned Soviet Luna 24mission brought back samples of rock and soil from the moon. NASA's Genesisspacecraft should be the first since then come September, when it returns samples of the solar wind it has collected in space.
AP