Itokawa asteroid is 40% empty!

We know with reasonable certainty the composition of VERY few asteroids. Mapping orbits to find one heading our way is only step one - without an understanding of their compositions and structure, the chances of moving one, deflecting one, mining one or anything else are zero. There are less than 20 scientists in the world working on this issue directly - looking for an exciting line of work?

"Five years ago, we thought that we would see a big chunk of monolithic rock, that something so small doesn't have the ability to hold onto any pieces," says Erik Asphaug, a planetary scientist at the University of California in Santa Cruz, US, who is not involved with the mission. "Everything we suspected about it turned out to be wrong."

The spacecraft showed a surface littered with boulders and gravel, suggesting it was made of the debris from a larger asteroid that was shattered in a past collision.