Image of the near-Earth asteroid Itokawa. The boulder-free areas appear relatively smooth and are filled with small, uniformly sized particles. Univ Tokyo/JAXA/

Suspected but unverified for years; S-type asteroids are confirmed to be the source for most small meteorites that fall on earth, scientists have proved.

The analysis of asteroid dust brought by a Japanese spacecraft to earth last year, has confirmed identical materials to those found in meteorites on earth, which are believed to be some of the oldest objects in the solar system.

The discovery is based on the dust samples collected by Hayabusa, a spacecraft launched by the Japan Aerospace Exploration Agency in 2003, that visited the asteroid 25143 Itokawa.

Researchers studied particles less than four thousandths of inch in length and found them identical to the material that makes meteorites.

More than 1,500 grains of dust were collected from the sample chamber and analyzed by an international team.

The research confirmed that the asteroid was ancient and that Itokawa originated from a larger asteroid. They are primitive planetary bodies that record the history of the early solar system, said Tomoki Nakamura, a scientist at Tohoku University in Sendai, Japan, and an author on each of the studies.

Nakamur and his colleagues found mineral signatures that indicate Itokawa had once been heated to more than 1,472 degrees Fahrenheit (800 degrees Celsius) for an extended period, National Geographic reported.

According to the researchers dust has been lying on the asteroid's surface for about eight million years.