Synchrotron x-ray diffraction analysis and electron microscopy of Itokawa dust particles recovered by the spacecraft Hayabusa

Hayabusa spacecraft has successfully recovered many dust particles from S-type asteroid Itokawa. We performed analyses of these dust particles using synchrotron-radiation X-rays and electron microscopes and found that the asteroid is a very primitive, chemically-unfractionated body that formed in the early solar system. After formation as a 20-km size body, the internal temperature increased up to approximately 800degC and slowly cooled down. The present Itokawa is an asteroid made of broken pieces of an inner part of the pre-existing larger asteroid. (author)