Spacecraft grabs rock samples from asteroid

Last weekend a small Japanese spacecraft called Hayabusa achieved a notable first in solar-system exploration.

The Japanese Aerospace Exploration Agency announced it had soft-landed Hayabusa on the asteroid Itokawa, collected a sample from the surface and then successfully lifted off again.

The first attempt to land on November 20 was also successful but it failed to collect a sample. We have to look back over 30 years to the Apollo missions to the Moon to recall the last time a spacecraft landed on another celestial body and then took off again.

Hayabusa is at present 288 million km from Earth and signals take 16 minutes to reach it. It was launched from Earth in 2003 and arrived at the asteroid last September.

Hayabusa successfully entered orbit and began mapping the surface to select a suitable landing site. It will have to begin its long voyage back to Earth by December 12 and its precious samples will be parachuted to a landing in Australia in June 2007.

Scientific analysis of this small piece of asteroid should tell astronomers a great deal about the material that formed the planets as well as the conditions prevailing at the birth of the solar system, 4.5 billion years ago.

The potato-shaped asteroid is about 500m long and has an orbit that periodically brings it close to the Earth. The images obtained by Hayabusa show it has a surface unlike any other so far studied, the most surprising feature being that its boulder-strewn surface is apparently devoid of impact craters.

The most likely explanation is that Itokawa is not a true solid body but, rather, a rubble pile made up of rocks, ice and dust loosely held together by the very weak gravitational field.

As it passes close to a planet such as Earth its components get shaken up and any impact features are erased.

Now for the bright planets. Venus is the brilliant white object dominating our western sky after sunset and its nightly progress through Sagittarius, and soon into Capricorn, is easy to see.

Mars is also very bright, unmistakable in Aries in the northeast after sunset. We are now leaving Mars behind and won't see it this bright again for another 13 years.

Saturn rises in Cancer at 1am and is due north just before dawn, at which time Jupiter may be spotted very low in the east.

* Grant Christie is an astronomy researcher, who writes a monthly column for the Herald.