Green Daily

2008 marks a century since an meteorite maybe 100 feet in diameter blew up over Tunguska, Siberia with the force of more than 300 Hiroshima bombs. As we've only come to understand in the last few decades, events like this – and much bigger – have happened many times before and will certainly happen again. Comets and asteroids (the latter called meteorites when they land) can and do hit Earth. So what do we do when a rock the size of Texas comes hurtling towards us with no Bruce Willis to nuke it into tiny pieces?

Impact is the right word, and it could range from a little rock that blasts through your roof and crushes your new flatscreen to a massive "extinction level event' like the one that probably took out the dinosaurs. While a strike of that magnitude is unlikely during an average human lifetime, the latest research suggests that even an asteroid a couple of hundred feet in size could kill millions if it hit an urban area.

Calculating the probability of a dangerous strike is hard to do because we really don't know exactly how many "near-Earth objects" are out there, especially relatively small ones like the thing that flattened a sizeable parcel of Siberian real estate.

More than we were, but probably not as much as we should. Following a spike in public awareness after the release of two blockbuster "disaster from space" films in the 90's, astronomer David Morrison famously observed that the total number of people looking for doomsday rocks was no more than a lunch shift at a McDonald's restaurant. Not wanting to be responsible for the end of the world, in 1998 the US Congress tasked NASA with locating 90% of near-Earth objects more than .6 miles across. In 2005, funds were allocated to search for objects of 328 feet across or larger (of which there may be more than 300,000 out there), but it's a slow process.

Finding is only the first part of the equation - the second issue is what we should actually do if we locate an object that's headed on a collision course with Earth. Nuking the thing as in the movies is considered by most experts to be a stupid and dangerous idea, even if we had the ability to do it, which we don't. In fact, right now there's no practical plan in place to divert an incoming asteroid or comet. Other possible courses of action include positioning a heavy spacecraft near the object in the hope that the gravitational pull will change its course, or just figuring out where it's going to hit and evacuating the area.

Disast-o-meter rating: 4/10

The odds are long, but the consequences could be incredibly severe.

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