TOKYO—For the first time, a spacecraft has landed on and returned samples from a celestial body other than the moon. This morning, ecstatic Japanese officials confirmed that dust retrieved from the capsule of its Hayabusa spacecraft did indeed come from the asteroid Itokawa and is not earthly contamination. The microscopic bits had been under investigation since the capsule landed in the Australian outback last June after a trouble-plagued, 7-year roundtrip to the lumpy, potato-shaped asteroid.
Education and science minister Yoshiaki Takagi broke the news at a press conference here this morning, and the Japan Aerospace Exploration Agency (JAXA) later posted a press release on its Web site.
Hayabusa can now claim success in all aspects of its mission. It tested several spacecraft technologies expected to be useful for future deep-space missions. And in 2005, the craft collected and transmitted back to Earth remote-sensing data on the asteroid's elemental and mineral composition, density and gravity that "changed the paradigm of how we think of small asteroids," Paul Abell, a planetary scientist at the Planetary Science Institute in Tucson, Arizona, told Science earlier this year. As detailed in a collection of scientific reports in Science (2 June 2006, p. 1330), Itokawa, at least, proved to be a loose agglomeration of rubble rather then the solid rock asteroids were once thought to be.
Now that the collected dust has been confirmed to be from an asteroid, researchers expect studies of it to shed light on conditions in the early solar system when planetary bodies formed.
Bringing back this microscopic treasure wasn't easy. JAXA launched Hayabusa in 2003. Even before the craft reached Itokawa, a solar flare damaged its solar panels, one of its four main engines malfunctioned, and two of its three gyroscopelike reaction wheels, used to control attitude, wore out. The craft touched down on the asteroid, but the sample-collection mechanism apparently never worked. Then after a second touchdown, ground controllers lost contact completely and feared the spacecraft lost. When they established communication 7 weeks later, they found Hayabusa had been rocked by an "eruption" of most of its fuel from a damaged fuel line. To conserve what was left, controllers pointed it on a circuitous route home that added 3 years to the planned trip. The main body of the craft burned up in the skies over Australia as its separated capsule landed safely in the outback on 13 June.
Although the intended collection mechanism had failed, scientists hoped some dust kicked up by landing on the asteroid had nevertheless settled into two collection chambers. They found 1500 particles when they opened those chambers in a special clean room in Tokyo. Only after inspection and analysis by a scanning electron microscope did the researchers conclude that most of the specks of dust had telltale mineral compositions that are consistent with meteorites recovered on Earth and dissimilar to what is found in earthly rocks. "Most of [the particles] were judged to be of extraterrestrial origin, and definitely from asteroid Itokawa," the press release concludes.
"Until now, planetary exploration was a one-way trip," project manager Junichiro Kawaguchi said in a statement on the JAXA Web site. He adds that advances in spacecraft inspired by Hayabusa are likely to lead to future trips to the main asteroid belt, Jupiter, and beyond. "We're entering an age of discovery of our solar system."