Yeah, this whole Depression thing sucks miserably. But have a little perspective. It's a miracle that we're even here at all. Huge, angry balls of ice and rock have been soaring through space trying to kill us forever. But they have failed every single time! Well, okay, they nailed the dinosaurs, but dinosaurs were too big and stupid and we needed their flesh for fuel. Anyhoo, here, courtesy of the Discovery Channel, are just a few of the heavenly bullies that have failed in their dastardly plans to wipe out life on earth.

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!

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