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 the ory 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`.

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.

Turned into a `rocket engine` 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.-AFP