1. Asteroid: Tunguska event

Year: 1908

Proximity to Earth (number of times Earth/Moon distance): Exploded metres above ground in the Russian wilderness

In a nutshell: This asteroid or comet fragment was thought to have burned and flattened trees with a 10-15 megaton explosion just before it would have made landfall. Scientists estimate such an event happens every 300 years or so.

2. Asteroid: 1937 UB

Year: 1937

Proximity to Earth (number of times Earth/Moon distance): Twice the distance from the Earth to the Moon

In a nutshell: Long before this asteroid could have been detected in time—at the time—it passed razor-close to Earth—it's diameter? 1.2 km—more than enough to cause plenty of worldwide damage.

3. Asteroid: 4581 Asclepius (1989 FC)

Year: 1989

Proximity to Earth (number of times Earth/Moon distance): 700,000 km (About twice the distance from the Earth to the Moon)

In a nutshell: Most frighteningly, this 1 km-wide asteroid passed precisely where the Earth had been only six hours before.

4. Asteroid: 2002 MN

Year: 2002

Proximity to Earth (number of times Earth/Moon distance): 0.3 (120,000 km)

In a nutshell: This passed inside the Moon's orbit, missing Earth by a wide margin within the orbit. That's good news, as the 80-metre-wide asteroid would have caused damage over 2,000 square kilometres if it actually made contact with Earth.

5. Asteroid: 2002 FH

Year: 2004

Proximity to Earth (number of times Earth/Moon distance): 0.1 (42,000 km)

In a nutshell: LINEAR, the asteroid tracking robot telescope showed this 30 metre object would pass within the ream of some earth-orbiting satellites - the closest pass ever predicted up to this point.

Well, that's the good news. The bad news? More are on the way!