Let’s say an asteroid large enough to do some significant damage to Earth is headed our way and will make impact in, say, six months. Can we blow up asteroids? Better yet: what if we nukedan asteroid? Is that a thing?
It’s totally a thing. Some of the brightest minds in the world have studied what would happen if we blew up an asteroid, and the answer is… complicated. There are a lot of factors to consider: the size of the asteroid, how far away it is, what the asteroid is made of, etc. But rest assured: using a nuclear weapon to blow up and/or deflect an asteroid is something that NASA has spent a lot of time investigating.
What would actually happen if we nuked an asteroid? Why is it so complicated, exactly? Read on to find out!
Let’s say that everyone agreed that nuking an asteroid was a-okay and it’s something that we have to do to save humanity. Do we have the means? Yep!
Dave Dearborn, physicist at the Lawrence Livermore National Laboratory—and “one of the most experienced nuclear weapons designers on Earth”—tells Popular Mechanics that the US has what it needs in its stockpile of nuke-related tech to handle “objects up to kilometers in size.” In the terrifying event of something larger than that heading our way, Dearborn says we don’t have the technology just lying around, but “we know what to build.”
Bottom line: “Getting a nuke into space isn’t difficult.”
We have the means to launch a nuke into an asteroid, but will we ever really have a good reason to actually do it? If the asteroid was large enough to justify it and we only had a warning time of a few years or so (yes: years), then it is “generally accepted” that “only the nuclear bomb approach would work,” according to Keith A. Holsapple of the University of Washington in his study, “The Deflection of Menacing Rubble Pile Asteroids.”
Los Alamos National Laboratory astrophysicist Robert Weaver is among those that generally accept the nuclear option could be our last hope—under certain desperate circumstances. Weaver thinks nuclear is the only practical option if we only have as little as, say, a six-month lead time. “From my perspective, the nuclear option is for the surprise asteroid or comet that we haven’t seen before,” he told the journal National Security Science in 2013, “one that basically comes out of nowhere and gives us just a few months to respond.”
Weaver says non-nuclear options to deflect the asteroid, while possibly effective, would take a decade of planning and development and would have to be deployed years in advance of the collision. Nukes it is, then!
Yes, a lot could go wrong when you’re sending a nuclear weapon into space to kill a giant rock. But let’s focus on the positives. Could this actually work?
Possibly! Based on supercomputer simulations, a nuclear blast striking the Itokawa asteroid—“a quarter of a mile long and about half as wide” cluster of granite rocks resembling an ugly potato (pictured)—would effectively swat it away from our planet, also sending its many fragments soaring safely away from our lawns and faces. The blast would only propel Itokawa in the desired direction, however, if we hit it in a direction perpendicular to its motion. We couldn’t just launch a nuke straight at it.
Bong Wie, director of the Asteroid Deflection Research Center at Iowa State University, is also confident that his HAIV-delivered nuke could safely deflect “99 percent or more” of an asteroid’s pieces away from us, with those remaining burning up safely in the atmosphere.
Needless to say, there are naysayers. But what could actually go wrong?
So much depends on what this asteroid is literally made of. Dr. Philip Plait, author of Death from the Skies!: The Science Behind the End of the World, notes that an asteroid made almost entirely of solid iron—which is a lot of them, apparently—would not be destroyed by a nuke. What would happen? It would just get mad, basically. Instead of the iron asteroid exploding into a zillion little pieces, the nuke “might only warm it up a little.”
As asteroids bump and grind against each other in space, they can sometimes turn into floating piles of rubble. Gravity keeps them in an asteroid shape, but they’re actually a porous blob of flying rocks. What happens if you try to blow up a porous blob of flying rocks?
Dr. Philip Plait reports that asteroid expert Dan Durda explored that question in an experiment at the Southwest Research Institue in Boulder, CO. The results? Unlike a solid hunk of rock, the simulated flying rubble pile actually absorbs the damage of a blast. Durda says to imagine whacking a sandbag with a hammer. What happens? Thud. That’s it. Asteroid: 1. Humanity: 0.
Experts also say that a nuked asteroid could totally destroy our already fragile ozone layer. There’s a ton of chlorine and bromine in an asteroid, apparently, which would rain down on the ozone layer and just vaporize it.
As Captain Planet taught us, the ozone layer protects all animal and plant life on Earth from powerful, harmful UV rays. Because we all stopped using CFC-filled Aqua Net, as CNN reports, the ozone finally started healing in the summer of 2016. So for the sake of the ozone, going nuclear might have to remain a last-ditch option.
There’s also a chance that a blown-up asteroid could just reassemble, T-1000-style, back into (roughly) its original shape. Once it has pulled itself together, it could just come screaming down at the same speed it was before, like it was never nuked in the first place.
How is this even possible? Well, if the asteroid is not a solid chunk of rock but is instead a cluster of rocks held together by gravity, then an explosion that doesn’t send the individual rocks flying at a fast enough speed (called “escape velocity”) won’t get the job done.
At least one experiment at Los Alamos National Laboratory has shown that if we hit the right-sized asteroid with the right-sized blast at the right angle, this can be avoided, in theory, but it’s still a possibility.
So even if the scientific community was 100 percent on-board with the idea of nuking an asteroid—which they definitely are not—it would be difficult to convince the public and politicians to ride the Nuke Train. Considering the potential risks, it would be a geopolitical nightmare. Imagine the negotiations involved with, say, convincing a nation to “take one for the team” and allow some nuclear debris to fall within their borders.
Richard Tremayne-Smith, co-chairman of the International Academy of Astronautics (IAA) Planetary Defense Conference, imagines that plenty of euphemisms would be deployed alongside the nukes. His recommendation? “High Energy Impactor to Save the World.” Catchy!