Asteroid spotted that has 1.3% chance of crashing into Earth in 2032 | Asteroids

A 100 metre-wide asteroid has triggered global planetary defence procedures for the first time after telescope observations revealed it has a chance of colliding with Earth in 2032.

Asteroid 2024 YR4 was spotted by an automated telescope in Chile on 27 December last year but has since risen to the top of impact risk lists maintained by the US and European space agencies.

Based on measurements gathered so far, the asteroid has a 1.3% chance of smashing into Earth on 22 December 2032, or put another way, a nearly 99% probability of barrelling past without incident.

“Most likely this one will pass by harmlessly,” said Colin Snodgrass, a professor of planetary astronomy at the University of Edinburgh. “It just deserves a little more attention with telescopes until we can confirm that. The longer we follow its orbit, the more accurate our future predictions of its trajectory become.”

The asteroid ranks as a three on the Torino Impact Hazard Scale, indicating a close encounter that merits attention from astronomers because there is a 1% or greater chance of a collision in the next decade that would inflict “localised destruction”. The Torino scale ranges from zero, when there is no risk, to 10 when a collision is certain and poses a threat to the future of civilisation as we know it.

The only asteroid ever to receive a higher rating is Apophis which made headlines in 2004. Apophis was initially rated a four on the Torino scale but was later downgraded as observations showed that it posed no threat for at least a century.

Gareth Collins, professor of planetary science at Imperial College London, said that an increase in monitoring of near Earth objects will make detections like asteroid 2024 YR4 much more common. “At this stage, the best thing to do is to continue tracking the asteroid for as long as possible so that we can predict its trajectory with more confidence,” he said.

A space rock the size of asteroid 2024 YR4 would not unleash a mass extinction event as happened 66m years ago: the asteroid that triggered the demise of the dinosaurs was 10 to 15km wide. But 100 metre-wide space rocks, which impact Earth on average every few thousand years, still have the potential to cause catastrophic damage on the city scale.

The detection of the asteroid has activated two UN-endorsed global asteroid response groups. The International Asteroid Warning Network has swung into action to make further observations of the asteroid and narrow down uncertainties in its orbit. The Space Mission Planning Advisory Group has also been alerted. They would propose any plan to intervene, perhaps by deflecting the asteroid with an intercepting spacecraft, a technique tested in Nasa’s Dart mission.

The asteroid is now hurtling away from Earth in almost a straight line making it hard for astronomers to determine its orbit with high accuracy. Astronomers aim to make more detailed observations over the coming months before the rock fades from view. If those measurements do not rule out an impact in 2032, the asteroid will probably remain on space agencies’ risk lists until it comes back into view in 2028.

“The first step in the planetary defence response is to trigger further observations,” Snodgrass said. “If these observations don’t rule out an impact, the next steps will be more detailed characterisation measurements using telescopes, and discussion of what space agencies could do in terms of more detailed reconnaissance and eventually mitigation missions. This asteroid is of the scale that a mission like Dart could be effective, if required, so we have the technology and it has been tested.”