From Amnesia To Armageddon

People underestimate the risk of catastrophic events when they can’t think of any recent ones:

Take the possibility of a major impact by an asteroid or other near-Earth object. The last impact that did serious damage was the Tunguska event over central Russia in 1908 (though there was no actual impact with the surface of the Earth—an asteroid or comet roughly 300 feet across apparently exploded in the air). Small wonder, then, that “20 years ago the near-Earth-object field practically didn’t exist,” says Don Yeomans, who heads NASA’s near-Earth-object program. … Back then, “we had ‘the giggle factor’ when it was mentioned that these objects could be dangerous and could be looked for,” Yeomans says. “People would laugh and say, ‘Yeah, when was the last time?’ Simply because we didn’t see them, they didn’t take the threat as seriously as we have come to.”

But in 1993, astronomers Carolyn and Gene Shoemaker and David Levy spotted a comet (now called Shoemaker-Levy 9) on a collision course with Jupiter.

Millions saw the incredible video of the massive explosions. There were 21 separate impacts, the largest of which was 600 times more powerful than the entire world’s nuclear weapons arsenal. The crater it left was 7,500 miles across, almost big enough to reach from the North Pole to Rio de Janeiro. A single impact like that would have wiped out life on Earth. The movies Armageddon and Deep Impact followed in the next few years, along with a couple of ultimately false alerts from the astronomy community about possible near-Earth objects headed our way that got huge press coverage. In the past 10 years, funding for NASA’s work to spot objects that might collide with Earth has gone from practically nothing to more than $20 million a year, and we’ve located more than 90 percent of the big ones that could do serious damage.