Sydney - An asteroid the size of one or two large passenger buses on Monday passed just 12,000 kilometres from Earth, considerably nearer than the moon, which orbits at 380,000 kilometres.
The asteroid, called 2011 MD, passed over the southern Atlantic Ocean, off the coast of Antarctica at its closest approach, about 1714 GMT, National Geographic News service reported.
Earth's gravity field provided a sling-shot pivot for the space body, which is travelling again away from Earth on its wide orbit.
Earlier in the day, Fred Watson of the Australian Astronomical Observatory was confident that the asteroid would not enter Earth's atmosphere. He told ABC news that other asteroids pose a more real threat, such as Apophis, which is expected to come close to Earth in 2029.
The asteroid was travelling at an estimated 100,000km per hour, but was still visible for some hobby astronomers for a short time.
It was first discovered last Wednesday by researchers in New Mexico from the Massachusetts Institute of Technology (MIT). They estimated its width between 6.3 and 14 metres.
Such rock bodies pass this near to the Earth about every six years, Nasa estimates. - Sapa-dpa