While this is encouraging news, it is obvious that Japan is exercising caution, waiting for definitive proof that it is asteroid dust and not terrestrial contamination.
If it does turn out that Hayabusa managed to bring back some dust from the surface of asteroid Itokawa, although they may be small, these tiny dust particles represent an unprecedented achievement. This is the fist time that a space mission has successfully rendezvoused with an asteroid, landed (or, more accurately, "docked"), picked up a sample and then delivered it back to Earth.
But why is this so important? This question has far-reaching implications, not only for space technology, but for the future of our planet.
Putting it bluntly, we have very little idea about what asteroids are made of. Yes, we have a very general idea about the interior of asteroids by looking at the surface consistency, but precise measurements wont be available until we are able to study these lumps of space rock up-close.
Until we have an understanding about the evolution, consistency and components of asteroids (particularly those potentially hazardous asteroids, or "PHAs" for short), we'll have problems trying to decide how to best deal with them.
We can analyze meteorites on Earth to understand what materials we are likely to find inside asteroids, but the holy grail of asteroid missions would be to collect a pristine sample directly from an asteroid. Hopefully, this is what Hayabusa has done.
Also, asteroids represent something of an opportunity: they might be the focus of a space mining industry. To return a sample of an asteroid, no matter how tiny, will give us a glimpse into what materials we might be able to exploit in the future.
"Asteroids are a vast wealth of material resources, a million huge fortunes to be made someday," Al Globus, Senior Research Associate for Human Factors Research and Technology at San Jose State University at NASA Ames, told Discovery News. "We're getting our first hands-on look at that potential."
So whether you want to deflect a "killer" asteroid from a collision path with Earth or set up a refinery to plunder space rock's precious metals, collecting a sample from an asteroid's surface is a great first step toward understanding our solar system's interplanetary vagabonds a little better.