A NASA scientist says one day there could be an opportunity to mine resources from asteroids such as the one that has just passed by Earth.
The 2005 YU55 asteroid, which is the size of an aircraft carrier, came within about 325,000 kilometres of Earth.
A scientist at NASA's Jet Propulsion Laboratory in Pasadena, Jon Giorgini, says carbon-based asteroids, such as YU55, could yield thousands of tonnes of resources
He says another asteroid that scientists can see, contains about 131,000 times as much metal that has been mined in history, worth about $US971 thousand trillion.
Mr Giorgini says by studying YU55 in the decades ahead there would be a better idea about available resources.
The black asteroid delighting astronomers, who trained telescopes on the ancient body in hopes of learning more about its composition and origin as it zoomed past Earth.
With a diameter estimated at 400 metres, Asteroid 2005 YU 55 is the biggest asteroid to make a close pass by Earth since 1976.
During its closest approach, it was inside the orbit of the moon. It posed no threat to either the moon or Earth.
