The Imperative of Asteroid Defense

The aftermath of the Tunguska Event, an impact from space in central Siberia.

Check out this Op-Ed in today's New York Times from Russell Schweickart, former astronaut and co-chair of the Task Force on Planetary Defense.

Asteroid defense is a subject that doesn't get nearly enough attention.  Of course we don't want to alarm people, but at the same time, maybe people need to be a little more alarmed!  That may be the only way to really see some action on this front.

When you think about it, it's sort of surprising that we don't devote more energy to asteroid defense.  We actively scan the skies for near-Earth objects, but in terms of actually deflecting an asteroid from a collision, our plans at this point are only theoretical.  It's surprising because it seems like we should be able to get everyone on board with this mission.  For some people, space exploration is seen as an esoteric endeavor, lacking practical purpose.  But what could be more practical than defending the planet from a clear and present danger?  To me, asteroid defense should be much easier to rationalize than studying the geology of the Moon or sending astronauts to Mars. 

The problem is that this is an issue that sounds fanciful.  We've all seen Armageddon.  You start talking about preventing an asteroid collision and everyone thinks about Bruce Willis flying up there to blow it up, with Aerosmith providing the soundtrack.

But we all know what happened to the dinosaurs.  What's so far-fetched about an asteroid collision? 
Even though impacts of that size are exceedingly rare, smaller objects are much more common and can do plenty of destruction.  Let us not forget the Tunguska Event, the 1908 impact of a space object in central Russia that caused an explosion estimated to be as much as 1000 times more powerful than the atomic bomb dropped on Hiroshima.  That was more than 100 years ago, and it came down in such a remote corner of the Earth that few people other than space enthusiasts even know about it today.  But it could just as easily have come down in New York City, in 2008 rather than 1908.  As Schweickart points out, this sort of impact occurs every 200 to 300 years, statistically speaking.  But that doesn't mean we have nothing to worry about.  If you average two such impacts in 400 years, they don't have to be 200 years apart.

This is not the sort of project that we can put off indefinitely.  A mission to Mars can be delayed five or ten years and it won't make much difference; the lives of millions don't hang in the balance.  But what if we were to discover an object that's going to hit us in the next five years?  Is that sufficient lead time to get the project going today?  Would we have to contend with congressional skepticism?  I can hear the carpers now: "Are we really going to spend 10 billion dollars on a project to protect us from this rock you say is going to hit us?  We don't even know where it's going to land, do we?"

If there were more champions for this cause, I can imagine it might be similar to the fight over climate change.  There would be those who would want to prepare for it, and those who would think it costs too much to prevent something that might not cause any harm in our lifetime.  But think of the huge amounts of money spent on missile defense during the cold war.  That danger was very real, but ultimately, thankfully, nothing came of it.  The expenditures required for asteroid defense would be tiny by comparison.  But unlike the prospect of nuclear war, which was possible but avoidable, the impact of a large object from space is inevitable given enough time.  We just don't know when it might come.  It could be 100, 200 or 300 years from now, but it could be much sooner than that.  We owe it to the citizens of Earth -- even those who may not be born yet -- to start preparing for this scenario now.

President Obama's new plan for the future of NASA calls for a manned mission to an asteroid.  Assuming this directive is not changed in the years to come, this will be an astonishing achievement.  But even more than a manned mission to Mars, it may prove to be of vital importance to the future of life on Earth.  We won't just be going to look around and take some soil samples.  We'll be learning how to interact with an asteroid.  And one day that knowledge could save millions of lives.

Scientists will be quick to point out that catastrophic impacts are still quite rare, and furthermore, the chances that an impact will occur near a major metropolitan area are smaller still.  But we might not be able to determine the object's precise trajectory until it's too late.  An object capable of destruction equivalent to Tunguska could land anywhere on Earth, killing millions, or killing no one.  But a serious effort to plan for this contingency will be worth the cost no matter how many lives are at stake.  There are certainly more immediate concerns on our horizon, but such will always be the case until the day we find the big one coming straight for us.