Monday, February 11, 2013
Close Calls with Asteroids: The Burden of Knowledge
When something blew up over a remote part of Siberia near a river named Tunguska on June 30, 1908, the news took days to reach the rest of the world. More than a decade later, expeditions to the area found that entire forests of trees were flattened over hundreds of square miles. The scientific consensus of the cause of the “Tunguska event,” as it came to be called, is that an outer-space object roughly 100 meters (300 feet) in diameter exploded in the atmosphere with a force equal to a medium-size hydrogen bomb. If you were a benevolent Deity wishing to give mankind a wake-up call without doing serious damage, it would be hard to find a less-populated land mass over which to blow up a fast-moving meteorite. But the next one may not be so relatively harmless.
This week, we will have a close call with something similar. Asteroid 2012 DA14 is going to zoom within about 28,000 kilometers (roughly 17,000 miles) of earth about half past one in the afternoon on Tuesday (Central Standard Time). This is closer than the orbits of some satellites, although due to the object’s south-to-north trajectory, we don’t have to worry about losing any DirecTV shows. We know this thing isn’t going to hit us, and we know so much about its trajectory, because advanced radar tracking systems have defined its orbit precisely enough to allow such predictions. Although the object was discovered by optical telescopes a year or so ago, the last time it was in our vicinity, radar tracking provides the best information on orbital parameters because it gives you continuous direct readouts of distance and direction.
While we don’t have to worry about 2012 DA14 hitting us this time, there’s always the possibility that either it or another larger object will some day show up on our doorstep, so to speak, and head directly towards us. This leads to the intriguing question of how scientists who first figure out such dire news should handle it.
Seismologists in Italy can serve as an example of what can happen if you keep quiet or minimize something that later turns out to be a genuine hazard. Back on Oct. 29, 2012, I blogged about the conviction of some seismologists who were held responsible for the deaths of victims of the L’Aquila earthquake of Apr. 6, 2009. So downplaying a collision with an asteroid, for instance, can lead to trouble if you can be charged with understating a known danger.
On the other hand, suppose you calculate that the thing is going to hit a populated area—New York, say, or Mexico City. If even an object as small as the Tunguska meteorite headed toward one of these places, it would definitely lead to millions of fatalities, because the blast effects are similar to a multi-megaton hydrogen bomb. You call a news conference, announce the dire news, the authorities order mass evacuations (in which some panic leads to fatalities, incidentally)—and then the thing hiccups and lands in the Pacific Ocean in pieces so small that we don’t even get a tsunami out of it. Now you’re in hot water for being the worst Chicken Little of all time. You said the sky was falling, and it didn’t. Nobody wants predictions of mass disaster to be realized, but in this case if you as a scientist reach conclusions that point that way, it’s your obligation to speak out. But you’d better seek out some advice about dealing with the media first.
Once such a disaster appears to be in the offing, humanity would face the question of what to do about it. A science-fiction movie called “Armageddon” (1998) posed one answer, which has actually been studied for real in some detail: send a mission to the oncoming rock to blow it into an orbit that will miss the Earth. There are a lot of technical problems with this idea. For one thing, we have no experience with blowing up extraterrestrial objects, and we could easily make things worse if the attempt went awry. Instead of one large rock wiping out one city, we could have dozens of smaller radioactive rocks wiping out lots of cities. For another thing, depending on how soon we figured out the object’s presence and trajectory, there might simply not be enough time to mount our defense. Once the space race wound down, our ability to do space projects fast and correctly lagged, and it’s not clear we as a species could get our collective act together fast enough to agree on a path to pursue, let alone carry it out.
If it looked like a truly mega-scale ending-life-as-we-know-it event was coming, the social effects would be interesting, to say the least. The title “Armageddon,” of course, is from the New Testament’s Book of Revelation, which refers to a battlefield on which “the kings of the earth” gather, presumably for a final contest with the people of God, although the context does not make it clear exactly what goes on. But if you believe in Biblical prophecy, you will have to admit that there are clear indications of some kind of astronomical goings-on that are supposed to happen toward the end of the show: the sun being darkened, the moon turning to blood, and so on. It is probably a waste of time to try and figure out exactly what kind of orbital mechanics is required to produce the effects described in an apocalyptic work such as Revelation. But the basic message—that history will end with some sort of widespread natural cataclysm on Earth—is still clear, and worth considering.
Tomorrow, unless the calculations were way off, we can watch video coverage of the flyby of 2012 DA14 and wipe our collective brow and say, “Whew! That was close.” But it’s a gentle reminder that, no matter how clever we are with our doings here, there are some things that are still beyond our control.
Sources: I found descriptions of the asteroid 2012 DA14 and its near miss on the NASA website http://neo.jpl.nasa.gov/news/news177.html. I also referred to the Internet Movie Database (www.imdb.com) for information on “Armageddon,” and to Wikipedia’s “Tunguska event” for information on that phenomenon. The single reference to Armageddon in the New Testament occurs in Rev. 16:16.