NASA鈥檚 Stardust mission survived a daring flypast of the Comet Wild 2 on Friday and collected the first ever samples of comet dust. The material, which could reveal much about the early Solar System, will be returned to Earth in 2006.
As a bonus, the fly-by produced the best pictures ever taken of a comet, although these also revealed the conditions Stardust had to endure 鈥� described by one team member as 鈥渢errifying鈥�.
Stardust was launched in 1998 and mission scientists were apprehensive as the spacecraft hurtled to within 240 kilometres of the comet鈥檚 nucleus.
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This potentially hazardous plunge took it through a cloud of particles at a relative speed of 22,000 km/h. To protect the craft, special 鈥淲hipple鈥� shields were deployed to absorb and deflect the energy of impacting particles.
鈥淚 was amazed,鈥� said Ray Newburn, part of the Stardust team at NASA鈥檚 Jet Propulsion Laboratory in Pasadena, California, where the mission was designed and controlled. 鈥淚 wouldn鈥檛 have expected that much success鈥� for such a difficult project, he told New 杏吧原创.
Oversized racket
The mission鈥檚 primary objective was the capture of pristine particles from the comet. These were caught in the pores of a lightweight glass foam, itself held in a framework resembling an oversized tennis racket. The samples will be dropped to a desert landing site in Utah in two years and then detailed laboratory analysis will begin.
If the craft had been struck by a particle larger than one centimetre across, Newburn said, it would have blasted right through the Whipple shields and into the craft or its solar panels. Calculations had estimated there was about a one in 50 chance of this happening. 鈥淚t was nervous time, without a doubt,鈥� Newburn said.
The unprecedentedly detailed images of the nucleus, showing sharp-edged pitting and one particularly deep chasm, will help astronomers to understand the structure of cometary nuclei.
In particular, the pits are helping scientists explain how comets form the geyser-like jets of gas and dust that produce their spectacular tails. For the first time, Newburn said, 鈥渨e鈥檙e seeing what the places the jets come from look like鈥� and, as a result, 鈥渨e know a lot more already about the mechanism鈥�.
Stardust鈥檚 chief scientist, Don Brownlee of the University of Washington, said that 鈥渢he fantastic details shown in these images greatly exceed our expectations鈥� but may take some time to fully interpret.
Despite the palpable relief at JPL over the successful pass through the comet, Newburn cautions that the mission鈥檚 final phase 鈥� landing the samples on Earth 鈥� will be even riskier. But it will also produce the biggest payoff: 鈥淭here will much more science in the particles themselves,鈥� he said.