When it comes to discussing options to protect the Earth from asteroids, a vast majority of articles invariably reference the Michael Bay disaster film "Armageddon" and its explosive solution for averting doomsday. A new study from Johns Hopkins University, however, has found that large asteroids are harder to break up than we previously thought and, much like the shape-shifting villain in "Terminator 2," may actually reform after briefly fracturing.
In a paper published in the March issue of the journal Icarus, the researchers explain how new computer models allowed them to create a more complete picture of how a doomsday asteroid might react to a violent collision. Their work was based on simulations created nearly two decades earlier that showed how a 25-kilometer (15.5-mile) diameter target asteroid would be destroyed by a kilometer-wide (.6 miles) asteroid traveling at a speed of 5 kilometers per second.
While the earlier model took into account various factors such as mass, temperature and material brittleness, it didn't account for more detailed processes –– such as the rate of crack formation –– that occur in the immediate aftermath of a collision.
"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," Charles El Mir, a recent PhD graduate from the Whiting School of Engineering's Department of Mechanical Engineering and the paper's first author, said in a statement.
Broken, but not beaten
As the video above reveals, the simulation showed that not only does the asteroid not completely shatter, but its core retains enough gravitational pull on the fragmented pieces to pull itself back together. Even in this cracked form, the asteroid retained significant strength, the team found.
"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," El Mir added.
In 2022, NASA's DART (Double Asteroid Redirection Test) mission will help to expand our options for asteroid deflection by colliding a man-made "interstellar bullet" with a 500-foot object nicknamed "Didymoon." They'll then monitor any dynamic changes in momentum by the small space rock over the next several years. The data gathered through these observations will be vital to informing future defensive weapons again much larger objects.
"We are impacted fairly often by small asteroids, such as in the Chelyabinsk event a few years ago," K.T. Ramesh, a member of the Johns Hopkins team, said. "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."