In 1998, Deep Impact and Armageddon simultaneously struck on asteroids as the perfect disaster movie plot. What force better to bring together the people of the world then sudden destruction? However, a new study offers some depressing news for any would-be Bruce Willis: an incoming asteroid would likely be much more difficult to break up than previously imagined.
“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,” says Charles El Mir, a recent Ph.D graduate from the Johns Hopkins University’s Department of Mechanical Engineering and the paper’s first author, in a press statement.
For their study, El Mir’s team used a computer model called the Tonge-Ramesh model (TRM). They had an advantage: One member of the team was, in fact, K.T. Ramesh, director of the Hopkins Extreme Materials Institute. Like older models, the TRM is focused on looking at an asteroid’s mass, temperature, and material brittleness.
But the TRM’s advantage is that it also thinks small. In addition to the larger picture, it also incorporates micromechanics into its equations, meaning that it can better analyze how a hypothetical asteroid’s cracks would move through its body.
“Our question was, how much energy does it take to actually destroy an asteroid and break it into pieces?” says El Mir.
The TMR model looks at a hypothetical asteroid’s destruction in two phases. The first is in the fractions of a seconds immediately after the asteroid is hit, the second looks at how the asteroid fares in the hours after impact. For their hypothetical, they imagined an asteroid approximately a kilometer in diameter (0.62 miles) hitting a 25-kilometer diameter (15.5 miles) target asteroid directly, at an impact velocity of 5 kilometers per second (11,184 MPH).
The first phase of the attack shows an explosion of movement on the asteroid. Cracks form and spread through the asteroid at a rapid pace. These cracks seemingly multiply themselves in seconds, millions of them form. The asteroid itself partially begins to flow like sand. A crater is formed on the asteroid.
While this kilometer-sized object would change the asteroid, it would not take it out of commission. The hypothetical asteroid had cracked, but not completely, and still would retain significant strength on its voyage. Phase two shows that as the damaged fragments of the asteroid scatter, they would eventually be drawn back by the asteroid’s gravitational pull.
“We are impacted fairly often by small asteroids, such as in the Chelyabinsk event a few years ago,” says Ramesh. “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.”
Source: Johns Hopkins University
Originally posted on Popular Mechanics