Scientists have revealed the best way to stop an asteroid from demolishing earth. Photo / 123RF
Scientists have revealed the best way to stop an asteroid from demolishing earth. Photo / 123RF
In the eyes of Hollywood, there is only one way to deal with a meteorite heading for Earth: a nuclear bomb.
But unlike the people behind Armageddon or Deep Impact, scientists believe we can derail the path of a giant asteroid in other ways.
Data show that crashing a sacrificial spacecraft into an asteroid would be powerful enough to avoid almost all rocks hitting Earth, averting catastrophe.
Only asteroids wider than a kilometre would need a nuclear detonation to shift them off course, scientists now believe.
A rock this big is expected to hit our planet once every 700,000 years and would create a crater as big as Manchester. An impact of this size would cause global devastation and the possible collapse of civilisation, experts say.
Astronomers believe around 900 “near Earth objects” - defined as within 120 million miles of our sun - are more than 1km wide, and they have identified 95 per cent of them.
Nuclear warheads have long been, and continue to be, part of planetary defence plans, but only as a last resort.
A White House document recently said that the US would continue to study when a nuclear explosive device would be needed to prevent an asteroid apocalypse.
It is prudent, an official document states, “to continue research on the potential for nuclear explosive devices to be used for Potentially Hazardous Object deflection”.
Scientists have long believed that a nuclear bomb would be needed to protect our planet from any asteroid more than 600 metres wide.
But new data from Nasa’s Dart mission – which deliberately crashed a spacecraft into an asteroid – have prompted the decision to raise the threshold.
Launching a nuclear bomb into space would need global political agreement. It would also be extremely risky with no guarantees of success.
“A kinetic impactor, a spacecraft, will be a lot more precise because you can select the mass, the velocity and the direction of the impact; you can really control the deflection,” Ian Carnelli, a planetary defence expert at the European Space Agency (ESA), told The Telegraph.
“However, it is a lot more complex with a nuclear device, and that is before you get into the political discussion because nuclear explosions in space are banned by UN treaties.
Nasa's DART probe (foreground right) and Italian Space Agency's (ASI) LICIACube, (bottom right) at the Didymos system before impact with the asteroid Dimorphos. Photo / AP
“But even so, the nuclear device is not like you see in Armageddon where you send drillers to put the bomb in the core of the asteroid and destroy it, the idea is to detonate it at a certain distance from the asteroid.
“Triggering an explosion a certain distance away from an asteroid is extremely complex and nobody would agree to test it before a real threat is identified so you really would have a total lack of knowledge of how to do it.
“Whereas the kinetic impactor is a proven technique and the technology is ready now and it is much more controllable. It’s really the ideal deflection technique.”
Over the last decade, scientists across the world have been planning for the remote eventuality of an asteroid strike, and last year Nasa crashed Dart into an asteroid to see how effective physical collisions are at moving asteroids off course.
Dart landed on the asteroid Dimorphos on September 26, 2022, and new analysis has found that the impact was far more effective than scientific models had projected.
A follow-up ESA mission, called Hera, will launch in October 2024 and study the asteroid in more detail. It should reach Dimorphos by Christmas 2026.
Observations of Dimorphos’s new orbit around a larger asteroid called Didymos have already shown that the impact of Dart was more powerful than expected.
This, scientists believe, is because the dust ejected into the air from the collision gave the asteroid an extra push, a phenomenon called a “momentum enhancing factor”.
Scientists have never been able to study the inside of asteroids in detail so it was impossible to estimate how strong this effect would be in practice.
For Dart, the effect was assumed to be negligible. But analysis of the Dimorphos-Dart collision found it acted as a strong amplifier of the crash and created five times more thrust.
“When you think of an impact, you always have material from the asteroid that is thrown into space. Typically that’s the material that is excavated from the crater,” explained Mr Carnelli, who is the project manager of Hera.
“That ejecta generates an additional push that acts almost like a small engine and gives an additional force to the asteroid. The amount of ejecta was a lot, much higher than what any scientists had foreseen before Dart.
“Current results, without even having Hera to get the data that is needed to nail down this number, is between two and five, which means that you have up to a five-fold effect due to this object.
“That has a very important implication for planetary defence because it means we could actually use a kinetic impactor deflection technique for much larger asteroids because we know that it’s actually more efficient than we thought it could be.”
A kinetic impactor would be a spacecraft, he said, of around two tonnes in mass equipped with just solar panels, a camera and a navigation camera. Launching this from a rocket into an asteroid is easier, safer and quicker to do than launching a nuclear bomb, Mr Carnelli said.
“We are expanding the range of applicability of the kinetic impactor and that’s very good for the community because we know more than 95 per cent of the kilometre-sized asteroids and we know that none of those pose a threat to the Earth,” he added.
