Want to Blow Up an Asteroid? It’s Harder than You Think

Asteroids could pose a significant threat to Earth, but blowing one up is not as easy as it might seem. Previously, astronomers and engineers believed that larger asteroids — those that pose the greatest threat to Earth — would be fairly easy to break apart into smaller pieces. Cracks and fissures within their bodies would provide a “starting point” when attempting to fracture the body — or so the thinking went. Now, that idea appears to be in error, as a new study shows that asteroids are harder, and tougher, than previously believed.

Science fiction movies often show astronauts blowing up asteroids as they head toward our planet. In real life, however, small fragments may pose a greater danger to Earth than a single impact, turning a bullet into a shotgun blast. Still, astronomers are studying the problem, providing options in the event they spot a potentially-dangerous asteroid headed our way.

“It may sound like science fiction but a great deal of research considers asteroid collisions. For example, if there’s an asteroid coming at earth, are we better off breaking it into small pieces, or nudging it to go a different direction? And if the latter, how much force should we hit it with to move it away without causing it to break? These are actual questions under consideration,” said Charles El Mir, a recent doctoral graduate from Johns Hopkins University.

The vapor trail left by the Chelyabinsk meteor event in Russia in 2013, when a house-sized asteroid encountered the atmosphere of Earth. This image was taken about 200 kilometers (125 miles) from the center of the explosion. Image credit: Alex Alishevskikh

Asteroid collisions were simulated through the use of computer models, in an effort to determine optimal strategies for deflecting or destroying these objects. Earlier computer models predicted that asteroids could easily be shattered in a collision with a significantly larger body. However, these models did not fully take into account the limited speed cracks grow within asteroids. The new Tonge-Ramesh model used by researchers at Johns Hopkins utilizes a more detailed look of the structures of asteroids than previously available.

The new computer model suggests that immediately following an impact between two asteroids, cracks would quickly grow around the body of the target and a crater would form. Although the object would suffer damage within its core, the asteroid would be unlikely to shatter. Within hours, gravity would bring rubble back together, coalescing over the weakened, but still intact, core.

These images show how fragments of asteroids can coalesce around a damaged, but still intact, core in the hours following an impact by another body. Image credit: Charles El Mir/Johns Hopkins University

“We’re developing a lot of technologies for operating with precision around these kinds of bodies, and targeting locations on their surfaces, as well as characterizing their overall physical and chemical properties. You would need this information if you wanted to design an asteroid deflection mission,” said Dante Lauretta, principal investigator for the OSIRIS-REx mission, based at the University of Arizona in Tucson.

This video shows a computer model detailing the initial effects of an impact between two asteroids. Credit: Johns Hopkins University
Within hours after impact, fragments of an asteroid will begin to join together once more, under the influence of gravity. Credit: Johns Hopkins University

Earth is regularly impacted by smaller asteroids, and is occasionally visited by a larger body, such as the one that exploded over Chelyabinsk, Russia in 2013, injuring 1,100 people. So far, observers have not found an asteroid or comet headed toward our home world, but it is likely just a matter of time until such a threat is found. This research, and programs like it, can help investigators develop methods to deal with such a threat when it is seen headed our way.

In addition to preparing researchers for an incoming asteroid, this new study might also provide insight into the formation of the Solar System and provide methods to carry out mining on asteroids.