Specksthat Speak
Dust of time
Dust recovered from the asteroid Itokawa holds clues to the early solar system and a record of the space rock's life
Well, more than 1,500 specks, most less than 50 millionths of a meter in diameter. Plucked from the surface of the asteroid Itokawa by Japan's Hayabusa spacecraft, the tiny grains carry a record of the solar system's early days. Now, scientists have decoded the particles and read in them a tale of the asteroid's history, a story that spans billions of years, from the asteroid's birth to its future demise. Teams of scientists in Japan and elsewhere report their findings in six papers published in the Aug. 26Science. "I think they have done a stupendous job of characterizing and classifying this asteroid based on a pittance of material," says planetary scientist Hap McSween of the University of Tennessee in Knoxville. For starters, the dust reveals which type of asteroid is responsible for the meteorites that litter Earth, says planetary scientist Bill Bottke of the Southwest Research Institute in Boulder, Colo. Until Hayabusa returned with a sample of Itokawa's surface, scientists couldn't prove that stony S-type asteroids like Itokawa were the source of the most common space rocks hitting Earth, called ordinary chondrites. "Most of the time, when you see a shooting star, in all likelihood if it reached the ground it would be a chondrite," McSween says. The problem was that gazing at asteroids through a telescope produced a different set of spectral colors than the chunks that had fallen to Earth, says MIT planetary astronomer Richard Binzel. But Tomoki Nakamura of Tohoku University in Sendai, Japan and colleagues were able to link S-type asteroids with chondrites.
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