In April, scientists discovered an asteroid that had a roughly 1 in 2,500 chance of hitting Earth in six months’ time. As the weeks passed, and observations improved, they determined that the space rock – perhaps 2,200 feet across – was on target for central Europe, potentially harming a million people. Scientists, space agencies and civil-defense organizations scramble to find life-saving solutions, but soon determine it is too late. “The exercise showed that we basically had to take the hit,” said Lindley Johnson, a NASA planetary-defense officer. Luckily, it was all there: an exercise. But there might not be a next time. Scientists predict that There’s about a 100 percent chance of an asteroid larger than 460 feet hitting Earth every century. Depending on where such a rock landed on the planet, it could cause more casualties than any known natural disaster.
The good news is that NASA has plans for such a scenario. Later this month, the US space agency will launch DART (or Double Asteroid Redirection Test), a mission that will test techniques designed to deflect dangerous space objects. The bad news is that actually intercepting a killer asteroid can be a far more difficult and more costly undertaking.
Every day, more than 100 tons of space dust blows over Earth that burns up in the atmosphere. Twice a year, a much larger asteroid—the equivalent of an automobile—will cause a significant explosion before burning up. Between 2000 and 2013, the Comprehensive Nuclear-Test-Ban Treaty Organization detected 26 large asteroid explosions in the atmosphere, ranging in size from one to 600 kilotons. In contrast, the Hiroshima bomb measured 15 kilotons.
Every so often, there are close calls. In 2013, a 65-foot asteroid exploded 20 miles above Chelyabinsk, Russia, releasing about 500 kilotons of energy, breaking people’s legs and blowing out windows in thousands of buildings. Had the blast been near the ground, there could have been a major accident. A space rock that erupted six miles over Siberia in 1908 flattened 800 square miles of forest. An explosion of that scale in New York City would result in millions of casualties.
In the late 1990s, NASA began to pay more serious attention to this threat. “What’s more likely that we’re going to see some survival moment due to the asteroid? No, it’s not high,” said former Navy Secretary Sean O’Keefe, who led NASA from 2001 to 2005, on a Zoom call. “But to the extent it does, and you haven’t done anything to see what it is, it will take him to stop, to stop him…” He paused, and smiled. “We can’t just sit back and say that peace prayer is what we would counsel.”
In 2005, Congress mandated that NASA detect and track 90% of all near-Earth objects greater than 460 feet in diameter within 15 years. As of January, about 38% of the estimated 25,000 objects of that size had been found. NASA is now developing a space telescope to continue the search, with a planned launch in 2026. But without a plan for further action, the data it collects will be no more than a prediction of civilization’s destruction.
Fortunately, experts have been working on such plans for years. The most famous proposal, thanks in large part to Hollywood, is to set fire to an incoming rock to deflect or destroy a nuclear device. There’s another equally movie-worthy ‘gravity tractor’, which will work by flying a spacecraft next to an asteroid and slowly—over years or decades—turning its path. Finally, there’s the impactor concept behind the Dart spacecraft, which is expected to disrupt its orbit next year in the moonlight of a non-hazardous asteroid.
In the meantime, no one should rest. Although there are no known killer asteroids bound for Earth, the Chelyabinsk explosion surprised scientists—they were actually monitoring another asteroid passing that day—and, as recent simulations have shown, to come. A lot of preparation is needed to deal with the threat.
As a start, NASA should build on DART by testing a gravity-tractor deflection spacecraft. Although it sounds extreme, preparing for a nuclear-armed mission also makes sense; Earlier this year, researchers at Lawrence Livermore National Laboratory and the Air Force Institute of Technology published a study on exactly that. Finally, as a 2018 report from the National Science and Technology Council suggested, the US should begin evaluating global launch capabilities—and developing international protocols—in the event that rapid response missions are needed.
For now, these may seem like far-fetched thoughts. But when that city-killing rock hurtles toward Earth, the only question anyone will be asking is: Who’s ready to launch?
Adam Minter is a Bloomberg Opinion columnist and author of Junkyard Planet: Travels in the Billion-Dollar Trash Trade.
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