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 12 ASTRONOMY • JULY 2019 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 cal