Newsback - Visiting an asteroid

The Japanese spacecraft Hayabusa appears to have successfully collected a sample from asteroid Itokawa on Saturday, after a failed attempt earlier in the week. The sample, containing dust that arose after a metal projectile was shot into the surface of the asteroid, will return to Earth in June 2007, landing in the Australian outback. Until the spacecraft returns, we won't know for sure whether or not the sample was in fact gathered. If it was, this will be the first time that scientists will be able to analyze material from an asteroid in the laboratory. Smaller bodies in the solar system, like asteroids, have likely gone through a lot less change since the formation of the solar system, so a close-up look at an asteroid is going to be a window back in time, back to the earliest days of the solar system when our own planet was forming. A NASA mission, NEAR (the Near Earth Asteroid Rendezvous), made a rendezvous with asteroid Eros in 2000 and landed on the asteroid in 2001, but did not return a sample.

Whether or not a sample gets here safely, the mission has returned some intriguing images of this rather peculiar-looking asteroid. As you can see in this recent Astronomy Picture of the Day, Itokawa has no craters, which is kind of strange, and looks rather warty due to rocks sticking up from the surface. It looks something like an oddly shaped pickle. It's possible that the asteroid is so loosely held together that craters are filled in when dust from the surface gets jostled by the relatively close passage of a larger object, like Earth (Itokawa orbits the sun roughly between Earth and Mars, but its orbit crosses that of Earth). Alternatively, the dust may gather an electrical charge (from sunlight or the solar wind of particles coming from the sun), and rise from the surface because the charged dust particles repel each other. The dust, dancing over the surface, might fill in any craters that form. There are more pictures available on the JAXA web site (the text is in Japanese).

The landing and sample retrieval on Itokawa was very brief, essentially a touchdown that lasted only a few seconds, just long enough to collect the sample. It hasn't been an entirely easy mission. During an earlier try at landing, the Japanese space agency JAXA wasn't able to communicate with the spacecraft, and wasn't aware that it had landed briefly until well after it took off again. Now on the return flight, the spacecraft has been placed in safe mode because it's undergoing unexpected vibrations, perhaps as a result of a leaky thruster. Time will tell what information this mission will give us about the origin of the solar system.