PRAGUE -- Scientists won't know whether Japan's Hayabusa probe actually returned asteroid dust until at least February or March, when researchers finish extracting microscopic particles from the craft's return capsule and complete an exhaustive analysis to verify their origin.

An image of one particle inside Hayabusa's sample canister. Credit: JAXA

In a presentation at the 61st International Astronautical Congress here, Hayabusa's project manager said he is optimistic the hard-luck $200 million mission returned at least some traces of asteroid material from the surface of Itokawa, the potato-shaped rubble pile object the probe visited in late 2005.

The trick is distinguishing the precious samples from contamination from Earth.

"Many of the particles are probably Earth particles," Kawaguchi said Wednesday. "However, some of the particles were probably captured at the asteroid."

Inside an ultra-clean room at the Japan Aerospace Exploration Agency's curation facility at Sagamihara, workers garbed in special bunny suits have been slowly extracting particles from one of two chambers inside the sample return canister.

The capsule fell back to Earth in June, touching down within 500 meters of its planned landing site at the Woomera protected area in Australia.

Kawaguchi said his science team found "tens of particles" in Chamber A of the canister. The tiny particles are being removed one-by-one in an extraction process that is stretching longer than anticipated.

Analysis of the samples will not begin until at least December, according to Kawaguchi.

JAXA's curation facility in Sagamihara, Japan. Credit: JAXA

"We will transmit any scientific update when it's available," Kawaguchi said.

Scientists still have not opened Chamber B, which likely holds more dust and asteroid residue than the container officials are already examining.

Chamber B should have been exposed to more asteroid material because of its location on the sample collection system. It lies on the side of the spacecraft that touched Itokawa with the most force during its time at the asteroid, Kawaguchi said.

Officials hope the force kicked up rocks and dust and funneled the samples into the collection device.

The opening of Chamber B is scheduled for October, Kawaguchi told Spaceflight Now.

Hayabusa was designed to gather several hundred milligrams of material if the sampling procedure went as planned, but the craft's projectile gun did not activate when it approached the asteroid.

Kawaguchi, who guarded his optimism before Hayabusa landed, now openly says he believes scientists will ultimately prove the mission returned pieces of an asteroid.

"Even a micron-sized particle can be sliced into bits and pieces and analyzed," Kawaguchi said.