We Might Be Able to Nuke Asteroids to Save the Planet After All

For years, the conventional wisdom has been that you can’t just nuke an incoming asteroid to save the planet, no matter what Hollywood movies have told you. The logic is quite straightforward; blowing space rocks into pieces would cause an even deadlier rain of smaller astroids that would pelt the entire surface of Earth. However, a new simulation from researchers at Lawrence Livermore National Laboratory (LLNL) suggests that nuclear “disruption” of an asteroid might be a viable option, even if the expected impact is just months away. Of course, it’s only possible if you can deliver a spacecraft to the asteroid, which still requires a lot of planning.

A sufficiently large space rock could mean game over for humanity. In a best-case scenario, we would know about that asteroid far in advance and can prepare a strategy to deflect it. NASA is about to begin work on the Double Asteroid Redirection Test (DART), which will send a spacecraft to the double asteroid system known as Didymos. The hope is that by cashing the DART impactor into Dimorphos, the smaller of the two rocks, it will be able to alter the trajectory. If successful, this could be scaled up to knock a dangerous asteroid off course. Without a large lead time, a redirect won’t work, and that could leave us with (literally) the nuclear option.

According to lead author Patrick King, there is reason to think that a nuclear weapon could save us. Using a program called Spheral developed at LLNL, King modeled the effects of a one-megaton nuclear weapon exploding just above the surface of a 100-meter asteroid. The simulation can estimate the effects on the asteroid body, as well as follow the course of fragments left over after the explosion. It even factored in the gravitational impact of other objects in the solar system.

After testing the hypothetical asteroid on five different orbits, the study concluded that 99 percent of the fragments from a shattered asteroid would miss the planet, as long as we manage to hit it more than a month before impact. The outcome is even better if we have more time. With two months until fiery death rains down upon the planet, a nuke can divert 99.9 percent of the asteroid’s mass.

So far, we’ve only talked about small 100-meter objects. While these are potentially dangerous, the extinction-level rocks are at least several times larger. However, a nuclear strike might help here, too. King found that a larger asteroid could be blown to pieces six months prior to impact, and 99 percent of the debris would miss us. The timeline might be an issue, depending on how early we spot the asteroid. Missions like OSIRIS-REx and JAXA’s Hayabusa2 have successfully landed on asteroids, but they were in the planning phase for years.

We’re only beginning to learn about the composition of asteroids, so the simulation might include some incorrect assumptions. For example, asteroids like Bennu might be built more like rubble piles than mountains, making them less dense and easier to disrupt. Missions like DART will help hammer down the details. NASA plans to launch the spacecraft on November 23rd, and it will reach its target in about 11 months.

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