It has been over 100 years since a big asteroid slammed into Planet Earth; the famous Tunguska Event in Russia flattened trees for miles around. Scientists and space nerds eagerly awaited the close arrival of another big one last week that was scheduled to miss us by about 14 minutes, coming closer than the moon and even closer than some of our satellites.
This rare close encounter of 2012DA14, which was only discovered last year, spawned much discussion about the utility of improving detection of all these nearby rocks, especially since sooner or later one of them seems bound to hit a populated area.
Stunningly, twelve hours before this once-in-a-century asteroid event, another once-in-a-century event came out of nowhere in the form of a smaller asteroid that actually did hit Earth in the same country that saw the last once-in-century asteroid. It exploded over a populated area, injuring over a thousand people who stood too close to glass windows that shattered while they were gaping at the unexpected fireball.
It was almost unbelievable that the two events were unconnected, but it appears that the meteor crashed from a completely opposite direction while 2012DA14 was still several moon lengths away!
The Case For Detection
Clearly we still have a lot to learn about space; maybe these once-in-century events aren’t so “once-in-a-century” after all. Giant rock balls could come crashing into our planet at any time. In fact, tiny ones disintegrate in our atmosphere every day. As enough time goes by, the enormous pool table of the solar system could bring our hurtling planet into contact with less common but even bigger hurtling rocks that could destroy civilization or at least a few cities.
Scientists say they’d identified almost all the civilization-threatening rocks for at least the next hundred years or so, and some of the city-threatening ones. Many of those – like 2012DA14 – sometimes don’t get discovered more than a year out. And we haven’t even begun to detect the non-tempered-glass-in-buildings-threatening size.
The huge gaps in our knowledge seem to beckon for more detection resources. If we discover the big ones a few years earlier, it becomes a whole lot easier to think about deflecting them. If we discover the medium ones even a couple weeks earlier, it becomes a whole lot easier to evacuate an area. No matter what, more detection of more asteroids seems like a guaranteed win for humanity.
Besides, what if the two recent asteroids were connected in ways we don’t understand yet? You never know when a rogue comet is going to disrupt the asteroid belt or when one of our old probes will fall into a black hole and come back to clear out our carbon-based infestation, right?
There’s a bit of an appeal to Pascal’s lesser-known Asteroid Wager: if we detect something that would have killed lots of people and deflect it, then it was worth it. If we don’t ever detect something, well, at least we haven’t lost anything.
The Case Against Detection
But it’s not quite true that we wouldn’t have lost anything. It is impossible to conclusively identify every single asteroid of every size that will ever hit the Earth; it’s just a matter of how many we’re going to identify, and how early. The harder we work, the greater the opportunity cost of what we could have done with those resources.
I think there’s a pretty good case that our current detection levels are good enough – or almost there. Even the moderately scary-sized ones seem to come along pretty rarely. When they don’t miss, they have a 75% chance of hitting ocean, and even if they hit land they have a good chance of avoiding people.
If the biggest asteroid to hit Earth in a century didn’t kill anybody, does that really justify throwing more resources into detecting them – especially if we’re already doing fine tracking the really big ones? How many more millions of people in the next hundred years will be killed by wars and diseases and accidents and bad government policies and other tragedies that are perhaps more deserving of our limited resources?
Sure, it’s always theoretically possible that a bunch of meteors will suddenly make a beeline toward us from all over the galaxy due to some unexpected universal wormhole degradation, but if you’re going to appeal to “the uncertainty of forces we don’t yet understand,” you might as well say that the Earth’s core could suddenly stop spinning or that aliens might be hiding under Antarctica; there’s no end of potential scenarios you might want to prepare for.
A Public Good-Enough?
Products with such large uncertain values are generally best left to the markets; people that are more interested and concerned can contribute to their production, and people that are skeptical don’t have to get involved.
But asteroid detection is a pretty iconic example of a public good; it can benefit everyone on the planet whether they contribute or not, so it will tend to be undersupplied, and it might be hard to know if it’s too undersupplied until it’s too late.
But we have enough detection in place already that I suspect the opportunity cost may outweigh the benefits of discovering the rest of those car-sized asteroids a couple days earlier. Of course, I’m not highly confident on that, so you’re not going to find me denouncing all asteroid detection plans as wasteful; I don’t really mind hearing that NASA is chucking a few mil towards better detection. I’m also excited that technological advances are lowering the costs and making it easier for non-government resources to get involved: I hope the B612 Foundation succeeds.
But at the end of the day, it’s not something that keeps me up at night.
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