A space probe thought to have landed on an asteroid last month may not have collected surface samples, calling into question the success of the unprecedented mission to bring extraterrestrial material back to Earth, an official said Wednesday.

Data from the Hayabusa probe, now hovering several kilometers from the Itokawa asteroid, did not indicate that the vessel had fired metal projectiles onto the asteroid's surface during its landing, as previously thought, said Seiji Oyama of the Japan Aerospace Exploration Agency.

Now JAXA will not know if the Hayabusa collected surface samples until the probe returns to Earth, Oyama said. The return is set for June 2007, glitch notwithstanding.

JAXA had announced on Nov. 26 that the Hayabusa appeared to have touched down for a few seconds on Itokawa, about 290 million km from Earth, firing two metal projectiles to collect the dust that was kicked up before lifting off again to transmit data to mission controllers.

The probe experienced trouble with its thruster after taking off from Itokawa, forcing JAXA to shut down the engines.

The agency has until Saturday to fix the problem before the probe must start its journey back to Earth. Any delay would make a return by June 2007 unlikely because the Hayabusa's orbit around the sun would take it away from Earth for two years.