The asteroid 2009 FH, which is about 20 meters across and was first observed on Tuesday, will come closest to Earth at 12.17 GMT, when the distance between the asteroid and Earth will be only 85,000 kilometers.
On March 2, a 35-meter asteroid came within 72,000 kilometers of Earth. The size of both space rocks is comparable to the asteroid that caused the Tunguska disaster, but there is no danger of a collision.
On June 30, 1908, an explosion equivalent to between 5 and 30 megatons of TNT occurred near the Podkamennaya Tunguska River in a remote region of Siberia.
The Tunguska blast flattened 80 million trees, destroying an area of around 2,150 sq km (830 sq miles).
It is assumed that a huge meteorite had hit the area, although research expeditions failed to find an obvious crater.
If the impact had occurred some 4 hours and 47 minutes later, the Earth's rotation means it would have completely destroyed the then Russian imperial capital of St. Petersburg.
