PARIS: Humanity could use a nuclear bomb to deflect a massive, life-threatening asteroid hurtling towards Earth in the future, according to scientists who tested the theory in the laboratory by blasting X-rays at a marble-sized “mock asteroid”. The biggest real-life test of our planetary defences was carried out in 2022, when Nasa’s fridge-sized Dart spacecraft smashed into a 160-metre wide asteroid, successfully knocking it well off course. But for bigger asteroids, merely crashing spaceships into them will probably not do the trick. When the roughly 10-kilometre wide Chicxulub asteroid struck the Yucatan peninsula around 66 million years ago, it is believed to have plunged Earth into darkness, sent kilometres-high tsunamis rippling around the globe and killed three quarters of all life — including wiping out the dinosaurs. We humans are hoping to avoid a similar fate. There is no current threat looming, but scientists have been working on how to stave off any big asteroids that could come our way in the future. A leading theory has been to be blow them up with a nuclear bomb — a last-ditch plan famously depicted in the 1998 sci-fi action movie “Armageddon”. There is no current threat looming, but scientists have been working on how to stave off any big asteroids that could come our way in the future In the movie, Bruce Willis and a plucky team of drillers save Earth from an asteroid 1,000 kilometres wide — roughly the size of Texas. For a proof-of-concept study published in the journal Nature Physics this week, a team of US scientists worked on a much smaller scale, taking aim at a mock asteroid just 12 millimetres wide. To test whether the theory would work, they used what was billed as the world’s largest X-ray machine at Sandia National Laboratories in Albuquerque, New Mexico. The machine is capable of generating “the brightest flash of X-rays in the world using 80 trillion watts of electricity”, Sandia’s Nathan Moore, the lead study author, said. Much of the energy created by a nuclear explosion is in the form of X-rays. Since there is no air in space, there would be no shockwave or fireball. But the X-rays still pack a powerful punch. For the lab experiment, the X-rays easily vaporised the surface of the mock asteroid. The vaporising material then propelled the mock asteroid in the opposite direction, so that it effectively “turned into a rocket engine,” Moore said. It reached speeds of 250 kilometres an hour, “about as fast as a high-speed train,” he added. The test marked the first time that predictions about how X-rays would affect an asteroid had been confirmed, Moore said. “It really proves this concept could work.” The scientists used modelling to scale up their experiment, estimating that X-rays from a nuclear blast could deflect an asteroid up to four kilometres wide — if given enough advanced notice. The biggest asteroids are the easiest to detect ahead of time, so “this approach could be quite viable” even for asteroids the size of the dinosaur-killing Chicxulub, Moore said.