The Japan Aerospace Exploration Agency announced Monday they found particles inside the Hayabusa mission's capsule that was supposed to scoop up a sample from the surface of asteroid Itokawa in 2005.

This image shows the dust particles inside the Hayabusa sample container. Credit: JAXA

Officials say they don't know yet whether the particles are dust from the asteroid, or if the material originated from Earth or interplanetary space.

Hayabusa's return capsule parachuted back to Earth in the Australian outback June 13, wrapping up a mission spanning seven years and stretching four billion miles across the solar system. The mission accomplished the first roundtrip journey to an asteroid.

The 16-inch-wide capsule returned unscathed, and recovery teams shipped the craft back to Japan, where it arrived June 18 at a high-tech curation facility in Sagamihara, near Tokyo.

An X-ray of the canister showed no signs of any particles larger than 1 millimeter, or about 1/25 of an inch, JAXA officials said in an earlier statement.

Technicians also measured a trace gas coming from the capsule.

JAXA released confirmation of the dust particles Monday in an update posted on the agency's Japanese language website. The discovery came after scientists opened up the canister.

The dust could have come from asteroid Itokawa, interplanetary space, or it could be contamination from Earth that was inside the container before launch or after landing.

The sample canister after it was removed from the Hayabusa re-entry capsule. Credit: JAXA

Only detailed analyses of the material will determine its source, according to JAXA.

Officials say it could be months before scientists definitely prove whether the samples were collected from the surface of Itokawa, a potato-shaped rock slightly larger than a typical city block.

Researchers plan to use a microscope and spectrometer to gauge the size, origin and chemical make-up of the samples.

Hayabusa was designed to gather samples using a gun-fired projectile to blast chunks of rock into a funnel leading inside the collection chamber, all while executing a touch-and-go landing.

But the system malfunctioned during two tries in November 2005. Hayabusa unexpectedly landed on the asteroid for about 30 minutes on the first attempt.

A second sampling run went more smoothly, but data-crunching engineers said the bullet never fired, putting Hayabusa's primary science objective in doubt.

Despite the mishap, mission managers remained hopeful some asteroid dust migrated into the sample chamber as the probe bumped into its surface.