Asteroids are tougher than we thought

Asteroids are tougher than we thought

In many science fiction stories, a bomb is deployed to shatter

a life-threatening asteroid headed toward Earth. But a study published March 15 in Icarus shows that breaking up asteroids is actually quite difficult. “Asteroids are stronger than we used

to think and require more energy to be completely shattered,” said lead author Charles El Mir, of the Johns Hopkins University’s Department of Mechanical Engineering, in a press release. El Mir’s team simulated the

aftermath of a collision between a 15-mile-wide (25 kilometers) asteroid and a 0.75-mile-diameter (1.21 km) basalt impactor traveling at 3 miles (5 km) per second. They used recent advancements in our understanding of how rocks fracture and improved

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computer code to model the impact in two different stages. First, a material model followed shortterm fragmentation inside the asteroid within just a fraction of a second. Then, the code handed over the calculations to a different type of model, called an N-body model, which ran for hours after the collision, as the asteroid’s gravity influenced small pieces that might have been knocked away. The initial strike caused millions of

internal cracks to develop as the areas nearest the impact flowed like sand, forming a crater. But those cracks didn’t completely shatter the asteroid. Instead, they left a body large enough to gravitationally retrieve the pieces that had flown off, ultimately leading to the asteroid reassembling itself. These results differ significantly

from studies in the early 2000s, when code was used to simulate an identical collision, but led to a shattered asteroid. The older code, the researchers say, could not take into account the smaller-scale processes during the initial collision. Because cracks propagate through an asteroid with limited speed, the authors say, they can’t easily break it apart. Although the new work indicates a

Hollywood-style explosion wouldn’t stop an incoming asteroid, it is a step toward determining how to act in such a situation. The work also has applications, the researchers say, for asteroid mining, because material thrown off during the collision ended up scattered back over the surface — potentially exposing internal riches for easier access.