How to Stop a Killer Asteroid

Millions of miles away, an asteroid hurtles toward Earth, seemingly headed on a devastating collision course. Scientists scramble furiously to avert the imminent extinction of life as we know it. Families huddle for comfort while animals scurry for shelter. It seems the end is near…

I probably just wrote out a synopsis for a summer blockbuster movie coming out next year (you’re welcome Hollywood), but the truth is—no matter how unlikely the odds—that all of this is possible. Fortunately, it seems, MIT has us covered.

Bruce Willis will be collecting Social Security by the time the action heats up.

The nice thing about all the telescopes and arrays and unmanned spacecraft that we have is that were something like this ever to occur, we’d know pretty well in advance. In fact, as the article above notes, we know that the asteroid Apophis may approach Earth in 2029 and again in 2036. This is not really what the screenwriters for Armageddon had us believe.

Having such advance warning, however, is important, because it allows us to make only a small alteration (Apophis weighs 27 gigatons, YOU get out and push) that over time will project to a big enough change.

The idea at play here is that photons from the sun actually have the ability to push objects around. This is the concept behind solar sails, which are a form of propulsion that harnesses these photons (as well as gases) in much the same way a sailboat uses the wind. This is good, since it requires no further energy input from us.

So how exactly are we supposed to harness the sun’s power to move a giant asteroid? Paint, of course.

Don’t laugh. By coating the asteroid in reflective paint (it would take roughly 5 tons), the asteroid would be more affected by bouncing photons, and over the span of many years, would be pushed off-course. It’s a slow process (some estimates say it would take 20 years to have a sufficient effect), but it is a relatively practical answer to a tricky problem.

I suppose another part of the appeal to this approach is that once set in place, it ought to be fool-proof. There is much that could go wrong with trying to create an explosion that pushes the asteroid off course. It could push in the wrong direction, the imparted energy might be less than expected, the bomb could miss entirely, it might not detonate at all, etc.

Still, explosives should remain a strong option. Assuming an asteroid the size of Apophis and 20 years of advance notice (the same time it would take for the paint to work its magic), my amateur calculations seem to suggest that one atom bomb (upwards of 300,000 N of force) should be enough to do the trick (if all of the energy can be used to push in one direction). That’s very reasonable, especially when considering the payoff—averting certain calamity.

Good Guy NASA: saves us even when we slash their budget.

It seems then, that there are multiple potential options for how we might prevent an asteroid impact. The unsung hero might actually be the fact that we are able to predict the motion of millions of planetary and sub-planetary bodies in our solar system to give us a chance to do something. I guess to that I should say, “thanks for having our backs, NASA.”

Your Turn: What’s your big idea for averting a disaster, whether it be from space or (especially in the wake of Hurricane Sandy) a little closer to home?


Neel Joshi

Neel is a medical student who also does research on pediatric brain tumors. He is passionate about medicine and blogs about health, politics, weight loss, and more at The Soapbox. He also maintains a blogging "happy place" at OptimistPrime.


  1. A very interesting post indeed. I had no idea reflective paint could be an option, wow. Hopefully we won’t ever have to face this type of problem though. ;-)

    Anyway, you have a really fascinating blog here. Thank you for sharing!

  2. If we tried to stop it we’d be playing GOD! (I love that 1st scene in Armageddon: “Little Richard! Where are you?!”) I sincerely believe that anything we try, we’ll screw up. (Bombs and huge gobs of reflective paint slamming into all our space junk.) Maybe we could mount huge solar reflectors on tops of mountains. (Can you image the battles over that!) The photons could bounce off them and push the asteroid away! Might even help with that little climate change problem we’ve been having. ;=D

    • Well, if my options are betting on science or betting on certain doom, I’ll put my wager on science. After all, if I’m wrong, no one’s gonna be around to collect anyway!

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