BioEd Online

Japan's Hayabusa spacecraft may have succeeded in its second attempt to collect pieces of a small asteroid. If so, this will be the first time a sample has been collected for return to the Earth from any object in the Solar System apart from the Moon.

On 26 November, the Japan Aerospace Exploration Agency (JAXA) said data sent from Hayabusa shows that every stage of the sampling process went well. Agency engineers said it was almost certain that Hayabusa's sampler had touched down on the Itokawa asteroid as planned, and shot two metal pellets into the rock to throw up fragments of the surface. "I think we were able to collect a sample," said project manager Jun'ichiro Kawaguchi.

Hayabusa was launched in May 2003 and in September 2005, arrived at Itokawa - a potato-shaped, 540-metre-long asteroid located about 300 million kilometres from Earth. Hayabusa is expected to leave Itokawa by early December for its return journey. Whether a sample was definitely collected won't be known until the spacecraft reaches Earth in the summer of 2007.

To get this far, members of the Hayabusa team have endured a rough passage. Two of the craft's three reaction wheels, which stabilize the probe and help it to navigate, stopped working; the first failed in July and the second in October. Chemical engines on board were used instead, but their lower accuracy made landing more difficult and practice descents didn't go perfectly. In the first landing attempt on 20 November, Hayabusa seemed to park on the asteroid's hot surface for more than 30 minutes, and failed to collect a sample.

Time and fuel were running short, so the 26 November try was almost the last chance to collect a sample. "It was learning in real-time," says Donald Yeomans, US project scientist for Hayabusa and senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. With each attempt, he says, "they learned more and more about how the spacecraft behaves".

Balancing act

Still, concerns remain. Hayabusa lost its balance soon after departing from the asteroid. Engineers are investigating the cause, but one possibility is that the craft's long stay on Itokawa's hot surface during the first landing attempt damaged one or more of 12 chemical engines. That, combined with the two lost reaction wheels, means the probe could run out of fuel halfway home.

But astronomers have praised Hayabusa's achievements so far as showing the way for future asteroid missions - especially those involving the operation of ion-propulsion engines, the delivery of high-resolution images, sampling and autonomous navigation. Analysing the sample, assuming it makes it back to Earth, would also help answer questions about how the Solar System was created.

The mission is renewing Japan's confidence in space activities. JAXA has recently tried a string of high-risk missions, but has seen many failures over the past few years. "The success of Hayabusa has become a tailwind for Japan's space development," Hajime Inoue, JAXA's executive director, said at a press conference. "It proves that the way we have been doing things wasn't wrong."