How do you stop an asteroid from hitting Earth?

SCIENTISTS have begun gathering in the South Australia outback to collect a tiny space capsule that could help reduce the threat of asteroids colliding with Earth.

The capsule, from a Japanese spacecraft called Hayabusa, is expected to land at Woomera on Sunday night.

Hayabusa was launched by the Japanese Aerospace Exploration Agency (JAXA) in 2003 in the hope of learning more about how the solar system was created and how to deflect any celestial objects on a collision course with Earth.

The spacecraft rendezvoused with the Itokawa asteroid, 2.9 billion kilometres from Earth, in late 2005.

Any dust collected from the asteroid may help researchers learn how to reduce the threat of a potential asteroid impact in the future, says NASA'S Michael Zolensky.

"If you want to mitigate that hazard you have to know about the physical properties of asteroids, what they are made of, so they are important for that reason as well," Dr Zolensky said.