TOKYO (Reuters) - Japanese scientists were trying to track a space probe almost 300 million km from earth on Sunday, on a mission to bring back the world's first samples from an asteroid.
The unmanned Hayabusa probe -- the name means "falcon" in Japanese -- had been due to land on the surface of the 548-metre-long asteroid 25143 Itokawa for just one second after a voyage of two and a half years.
But it was unclear whether the probe had completed its delicate mission, a spokesman for the Japan Aerospace Exploration Agency said.
"The probe launched a landing target marker from a height of 40 metres, then descended to a position 17 metres from the asteroid," said a spokesman for JAXA. "We are not certain what happened after that."
Scientists were in communication with the probe and analysing data to try to calculate its exact position, thought to be close to the asteroid, but it was unclear whether there had been a technical problem, he said.
Asteroids, unlike larger space bodies such as the moon, are believed to contain rocks that have remained largely unchanged since the early days of the solar system and can thus offer valuable information about its origins.
Information about structure could also be vital if an asteroid were found to be on a collision course with the Earth.
Hayabusa was to have landed on Itokawa for just long enough to allow it to fire a metal pellet into its surface and collect a sample of the material stirred up by the impact.
Failure would be an embarrassment for Japan's space industry, recently overshadowed by Asian rival China's success in carrying out manned space flights -- something Japan has never attempted.
Hayabusa has already sent back a series of detailed photographs of the asteroid, which Japanese media noted looked something like a potato. In the most recent photograph, taken on Sunday and published on JAXA's Web site, the probe's shadow can be made out on Itokawa's surface.
But the mission has also been dogged by problems.
Last week it failed in an attempt to launch a miniature robot onto the asteroid's surface to collect data. The robot, the Minerva, went missing after being released from the probe.
The 500-kg Hayabusa has also developed a problem with its positioning control system, while a solar flare damaged its wing-like solar panels.
The mission is scheduled to carry out two touchdowns on the asteroid before Hayabusa heads back to earth, where the sample is due to land in the Australian outback in June 2007, four years after the probe was launched.
Itokawa is named after pioneering Japanese rocket scientist Hideo Itokawa.
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