In recent years, there's been some uncertainty as to how we should deal with a nasty-looking asteroid tumbling toward Earth. If we're to believe the movies, we need to throw our nuclear arsenal at the offending space rock. But more recently, there have been some very strong arguments for more subtle asteroid deflection techniques.
Going against the recommendations of not using nuclear explosions destroy an asteroid on a collision course with Earth, physicist David Dearborn of the Lawrence Livermore National Laboratory has turned the "softly, softly" approach on its head.
Yes, prepare the missile silos again, it's time to detonate a 100 megaton firework.
Dearborn spoke at the semiannual meeting of the American Astronomical Society (AAS) last month after developing several computer models of nuclear detonations on or near different types of asteroids.
His results weren't very surprising: nuclear explosions work and they are a good way to protect the Earth from asteroid doom.
But isn't this result obvious? Doesn't the nuclear missile handbook have a chapter called "Alternative Uses: Blowing Up Doomsday Asteroids"? Bruce Willis taught us this lesson ages ago.
Actually, Dearborn didn't want to confirm what we were all thinking, he has come up with a strategy for the best use of nuclear weapons. A strategy that might be quite useful should astronomers see an extinction event asteroid on our doorstep.
Dearborn has outlined two general guidelines:
1) If the asteroid is small, and we have a few decades to deal with the threat, it would be best to detonate a nuke next to the asteroid to nudge it slightly off course.
2) If the asteroid is big, and we only have a few weeks notice, detonate a nuke on the asteroid, hopefully ripping it to shreds.
The main advantage of a nuclear explosion is that a massive amount of energy is released rapidly, making the technique highly efficient; a nuke can be used to nudge, knock, slow down, speed up or destroy the space rock.
Personally, while I agree with Dearborn that nukes are our most powerful defense against asteroids, there are many other factors to consider.
Firstly, what if the resulting explosion rips the asteroid to shreds, but big chunks of asteroid then rain down on Earth, blanket bombing entire continents? Choosing whether to get hit by one big asteroid or a shower of smaller (but still rather big) asteroid chunks isn't a choice I'd want to make.
Secondly, what if the USA fired a missile at a medium-sized asteroid, only to deflect it into China? Wars have started over much less.
Thirdly, we don't have a very good understanding about the structure of asteroids. An asteroid composed of very loose rock held together under a mutual gravity (a "rubble pile") will act very differently to a solid, metallic asteroid when faced with a huge explosion. President Obama's plan to send NASA astronauts to an asteroid to study it up close suddenly seems like a good idea.
Also, a recent study showed that a direct hit by a nuclear weapon might rip the offending asteroid apart, but it could re-form if the bomb wasn't big enough.
So what is it to be? Do we use nuclear weapons? Or do we find more subtle ways to deflect asteroids?
Unfortunately, it is highly unlikely there will be a "live" nuclear test in space, so it is doubtful we'll know the true impact of a nuclear asteroid strike.
But there's one thing for certain — and many experts agree — if we have less than a decade to deflect a killer asteroid, I'll be the first in line to press the Big Red Button, nuclear weaponry might be our only choice.