The goal is not just to foretell the date and time of a potential catastrophe. The goal is to forestall it. With years or decades of warning, a spacecraft, using its own minuscule gravity, might nudge a threatening asteroid off course. For objects requiring a bigger kick, a kamikaze spacecraft or a nuclear bomb might do the job. Vexing dilemmas would attend this showdown in space. How will governments decide to act? “This is a class of problem that the world isn’t set up to deal with,” says physicist David Dearborn, an advocate of a nuclear strike against an incoming asteroid.
Two facts are clear: Whether in 10 years or 500, a day of reckoning is inevitable. More heartening, for the first time ever we have the means to prevent a natural disaster of epic proportions.
Every day, dozens of tons of detritus from outer space—dust from comets, tiny shards of asteroids—burn up in the Earth’s upper atmosphere, leaving bright meteor trails at night. Most days a chunk or two of rock or metal, fist size or bigger, survives the fiery plunge.
Yet the odds of seeing a meteorite hit the ground, let alone being struck, are phenomenally low. Only one is known to have hit a person. Around 1 p.m. on November 30, 1954, a meteorite tore through the roof of a house near Sylacauga, Alabama, across the street from the Comet Drive-in Theatre. The rock, about the size of a softball, caromed off a console radio and clipped Ann Hodges as she snoozed on her couch, bruising her left hip and wrist. She was hospitalized to recover from the shock.
Since then, there have been some spectacular near misses. On August 10, 1972, an object around 15 feet across and weighing 150 tons skipped off the upper atmosphere. Hundreds of eyewitnesses saw the glowing streak, dazzling on a sunny afternoon, as it traversed the sky from Utah to Alberta before whizzing back out into space. On March 22, 1989, a rock as much as a thousand feet across came within a few hundred thousand miles of Earth—an uncomfortably close shave.