The first results from the Japanese Hayabusa mission have been presented here at the Lunar and Planetary Science conference, and have generally got a warm response. Hayabusa visited the small asteroid Itokawa late last year, and managed to survey the lumpy rock in great detail, despite coping with some major technical problems.
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The Japanese Space Agency (JAXA) mission was largely about testing new spacecraft technology, such as Hayabusa’s xenon gas-powered ion drive. The ambitious project also hoped to land on the asteroid, grab some rocks and dust, and bring them back to Earth. It could still deliver the first sample ever returned from an asteroid.
Sadly, the sampling mechanism didn’t work, so scientists estimate that at best the craft may be carrying a few hundred milligrams of Itokawa that slipped into the collection pod by accident. Since it’s control system also broke, the crippled probe is now limping home using little puffs of its remaining xenon gas to steer. After making contact for the first time in three months on 6 March, Hayabusa is now expected to be back on Earth by 2010, which is way past its bedtime.
However, the probe did manage to land – well, bounce – twice. But it was only in contact for a few seconds before flying off into space again.
More successful was the earlier part of the mission, where Hayabusa hovered about 7 kilometres above Itokawa’s surface to take its vital statistics.
The asteroid – which always reminds me of a cosmic coprolith – has a surface area of 0.393 kilometres squared, and measures 535 x 294 x 209 metres. It appears to be very porous, implying that it is little more than a pile of rubble held loosely together.
By counting the number of craters on the surface, the science team confirm previous estimates that Itokawa was born between 10 and 100 million years ago. They suspect that it was created after an impact on a much larger asteroid threw up a spray of boulders, which then aggregated to create the misshapen asteroid. Itokawa is also rich in minerals like olivine and pyroxene, making it very similar to one of the most common types of meteorite.
Although not terribly surprising, this is all good for understanding where asteroids come from, where they go, and how we might go about deflecting one that is on a collision course with our planet. Many of the US scientists here made a real point of congratulating the Hayabusa team before they asked questions about the presentations. “It’s a pretty gutsy mission,” says Don Yeomans of NASA’s Jet Propulsion Laboratory, who leads Hayabusa’s US science team. But can the disabled craft really make it home? “I wouldn’t bet against it,” says Yeomans.