A study has poured cold water on the film theory that humans could simply blow up an asteroid on a collision course with Earth.

Asteroids and meteors are a prime candidate for wiping out humanity, just as one such impact 66 million years ago killed the dinosaurs.

One of the most popular theories - as famously illustrated in 1998 Bruce Willis film Armageddon - involved blowing up the asteroid before it hits Earth.

But a study by scientists at John Hopkins University in the US suggests this would be much harder than previously thought.

How asteroid fragments 'would reform under gravity'

It says blasted away fragments would be likely to reform with the asteroid because of gravity.


The researchers developed a new computer modelling method to examine how rock breaks apart in simulations of asteroid collisions.

"We used to believe that the larger the object, the more easily it would break, because bigger objects are more likely to have flaws," said Dr Charles El Mir.

"Our findings, however, show that asteroids are stronger than we used to think and require more energy to be completely shattered," he added.

The researchers separated their simulation into two different phases: a fragmentation phase following impact and a re-accumulation phase when the asteroid fragments were able to have a gravitational effect on each other.

In the first phase, millions of cracks formed and rippled throughout the asteroid immediately after the collision.

Parts of the asteroid rock flowed like sand and a crater was formed but, crucially, the whole of the asteroid wasn't broken by the impact.

Image: Space objects hitting Earth have dominated science fiction ideas about human extinction

The core of the asteroid was able to exert a strong gravitational pull on the fragments blasted away - meaning a lot more energy than thought would be needed to destroy an asteroid headed for Earth.

"It may sound like science fiction but a great deal of research considers asteroid collisions," said Dr El Mir, whose study is published in the journal Icarus.

"For example, if there's an asteroid coming at Earth, are we better off breaking it into small pieces, or nudging it to go a different direction?

"And if the latter, how much force should we hit it with to move it away without causing it to break? These are actual questions under consideration," added Dr El Mir.

"We are impacted fairly often by small asteroids, such as in the Chelyabinsk event a few years ago," said Dr KT Ramesh, a colleague of Dr Mir's.

"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."