KAGOSHIMA, Japan: Six weeks after blasting two spy satellites into orbit, Japan launched another rocket on Friday, this time carrying a spacecraft that scientists hope will bring back the first rock samples from an asteroid.

Taking off from Kagoshima in southern Japan, the Muses-C space probe is scheduled to visit the 1998 SF36 asteroid, 300 million kilometres from the Earth, and bring back a single gram of rock in four years' time.

"Asteroids are known as the fossils of the solar system," said mission leader Junichiro Kawaguchi of Japan's Institute of Space and Astronautical Science. "By examining them, you can find out what substances made up the solar system, including Earth, in the distant past."

The mission will cost at least US$160 million. If successful, it will be the first to bring back a rock sample from an asteroid, Kawaguchi said.

The United States launched a mission named "Stardust" in 1999, aimed at bringing back dust from the tail of a comet.

The spherical shape of most planets indicates they have been melted by tremendous heat, changing their chemical composition and making them less useful for research into the state of the solar system five billion years ago, Kawaguchi said.

Shaped like a rugby ball about 500 metres long, the target asteroid is twice as far away as the sun, but still one of the nearest to the Earth.

Muses-C is set to land on the asteroid's surface and fire a small projectile into the crust, scooping up the resulting rock fragments. Even a tiny amount will be sufficient for research purposes, Kawaguchi said.

On return to the Earth's atmosphere, the sample container is designed to break away from the probe and parachute back to land in the Australian desert.

Agencies via Xinhua