A rock measuring less than 10 metres (33 feet) across zipped past the Earth at the closest distance ever detected, but it would not have posed any threat if it had struck our planet, astronomers said Thursday.

The "very small" asteroid missed the Earth on March 31 by the wafer-thin gap of 6,500 kilometers (4,000 miles), according to an email circulated by the international network NEO News (NEO stands for Near-Earth Object).

Robot telescopes operated by NASA in New Mexico under the Spaceguard Survey to track potential threats from asteroids, spotted the object, 2004 FU 162, just a few hours before the flyby. "It would have exploded harmlessly in the upper atmosphere had it hit," the circular said.

Copyright Agence France-Presse, 2004