Scientific American November 2003 [antikvár]

^ SA Perspectives Penny-Wise, Planet-Foolish Somewhere in the inner solar system, there's a rock with our name on it. Literally. In March the International Astronomical Union named a newly discovered asteroid 14145 SciAm, on the recommendation of its discoverer, Edward Bowell of Lowell Observatory. Fortunately for the magazine's public relations image, the asteroid does not cross paths with Earth. Others after whom asteroids are named may not be so lucky. As most people now recognize, killer rocks are a fact of life on our planet. Doubters can ask the dinosaurs for their opinion. Is the world doing enough to cope with the threat of impacts? In this issue, a team of scientists and astronauts argues for going beyond the current telescope surveys to begin developing a rocket that could land on an asteroid and push it out of the danger zone [see "The Asteroid Tugboat," on page 34]. The project could cost $1 billion, spread out over a decade or so. Is it worth it? Some question whether we should spend even a penny on distant threats when we face so many immediate ones. One counterargument is that the world doesn't have the luxury of tackling its problems one by one. It needs to cope with many at once by allocating resources among them. Certain problems deserve more, others less—but all need something. Acmarial calculations can help us perform this juggling act. By the latest estimate, every year Earth has a one-in-600,000 chance of getting whacked by an asteroid wider than one kilometer—big enough to wreak global havoc and kill billions of people. Averaged out over time, several thousand people a year will die from ASTEROID 433 Eros, as seen by the NEAR Shoemaker probe. such impacts, which is greater than the toll from plane crashes or international terrorism. If you value their lives at $1 million apiece (a common ballpark figure used by insurers), you could justify putting several billion dollars each year into anti-asteroid efforts. This calculation is crude, but the conclusion is clear: the roughly $10 million a year that the world pays to scan for big asteroids is money well spent. What about extending the search to smaller ones? Because they are harder to find and would do less damage, the cost goes up and the benefit goes down. But recent studies, most notably a NASA report released in September, suggested that looking for the small guys still makes economic sense. Every year they have a roughly one-in-5,000 chance of taking out a city or triggering the mother of all tsunamis. On average, it works out to a couple hundred million dollars of damage a year. The search would cost a tenth of that. When it comes to making active preparations, however, the balance of cost and benefit is unclear. Should we get a jump on deflection technologies, evacuation plans and the like, or can we prudently wait until we're sure that an asteroid is headed our way? To answer that, the world needs a high-level, high-profile study conducted not just by astronomers and geologists but also by economists and disaster planners. One of the authors of the article in this issue, asteroidolo-gist Clark Chapman, has called for the National Academy of Sciences to weigh in. We agree. Human beings are notoriously inconsistent about evaluating risks. Even by that low standard, though, we are ill prepared for threats of the asteroidal kind— so devastating that our existence could be at stake yet so infrequent that they sound practically like fairy tales. The difficulty of comprehending the threat makes a sober, comprehensive and authoritative analysis all the more urgent. THE EDITORS [email protected]