How Hard Is It to Blow Up an Asteroid?

In the iconic 1998 movie "Armageddon," Bruce Willis (aka Harry Stamper) leads a group of misfit miners to drill into an asteroid threatening Earth and blow it up before it's too late. In fact, the threat of asteroids is a common theme in sci-fi movies, including "The Good Dinosaur" and "Seeking a Friend for the End of the World." But here's a sad spoiler alert: It probably is harder to destroy these asteroids than we thought.

Not Just Science Fiction

While incoming space rocks make for fun popcorn nights, in reality, the threat is super-serious. An asteroid might have killed the dinosaurs 66 million years ago. And it was only five years ago that a much smaller object broke up over Chelyabinsk, Russia, shattering glass and causing hundreds of reported injuries.

Watch Dash-Cam Footage of the Chelyabinsk Meteor

NASA (and many others) is on the case, scanning the sky for threatening objects and also setting up a Planetary Defense Coordination Office to work with other agencies in case an Earth-killing space rock is ever found. Both Japan and the United States are also studying two asteroids up close right now with the Hayabusa2 and OSIRIS-REx missions, in part to better characterize the potential threat of these tiny worlds. The good news? We don't know of an imminent threat to Earth. The bad news? The solar system is a big place, and it's statistically likely over hundreds or thousands of years that something big will inevitably hit Earth, so we must not give up the search, and we must remain vigilant.

And there are studies going on all the time about asteroids, including a new one about asteroid impacts that appears soon in the journal Icarus.

"We are impacted fairly often by small asteroids, such as in the Chelyabinsk event a few years ago," said study co-author K. T. Ramesh, the director of the Hopkins Extreme Materials Institute at Johns Hopkins University, in a statement. "It is only a matter of time before these questions go from being academic, to defining our response to a major threat. We need to have a good idea of what we should do when that time comes — and scientific efforts like this one are critical to help us make those decisions."

Cosmic Billiards

To get that idea, Ramesh and colleagues (including lead author Charles El Mir, a recent Ph.D. graduate) redid a study from the early 2000s, where a different research team made a computer model simulating an asteroid one kilometer (0.62 miles) across slamming into another asteroid 25 kilometers (15.6 miles) across. The old results looked reassuring — it suggested the bigger asteroid would be obliterated — but computer technology has come a long way in almost two decades. It's time to work on this again.

The new study rehashed the same scenario with a newer computer model, called Tonge-Ramesh, which takes into account factors such as how cracks spread in asteroids during collisions. Once investigators ran the model, they did indeed see cracks forming — but it wasn't enough to tear the asteroid apart. Instead, the core of the asteroid was damaged, but still intact enough to exert a gravitational pull on the fragments that were blasted off by the collision. It might have been cracked, but the asteroid was still mostly in one piece.

"We used to believe that the larger the object, the more easily it would break because bigger objects are more likely to have flaws. Our findings, however, show that asteroids are stronger than we used to think and require more energy to be completely shattered," said El Mir in the same statement.

That doesn't mean that it's all dire news; just that when we think about methods to protect Earth from asteroids, we may have to try something a bit stronger to destroy those space rocks. We also might need to think more creatively. Maybe a better approach might be to tug the asteroids away from Earth rather than blowing them up. Or maybe we'll get lucky and find a way to create "Star Trek"-like forcefields to keep asteroids away. Only time and technological development will tell.

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Learn more about the risks to our planet in "Death from the Skies!: The Science Behind the End of the World" by astronomer Phil Plait. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Elizabeth Howell March 7, 2019

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