Global planetary defence procedures have been triggered for the first time after a 100 metre-wide asteroid was revealed to have a chance of colliding with Earth.
On December 27, 2024, an automated telescope in Chile spotted Asteroid 2024 YRY but it has since risen to the top of impact risk lists maintained by US and European space agencies.
The asteroid has a 1.3% chance of colliding with Earth on 22 December 2032, meaning the risk is still small.
“Most likely this one will pass by harmlessly,” said Colin Snodgrass, a professor of planetary astronomy at the University of Edinburgh, speaking to The Guardian.
“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.”
On the Torino Impact Hazard Scale the asteroid ranks as a three, meaning there is a 1% or greater chance of a collision that would inflict “localised destruction”, which merits the attention of astronomers. The Torino scale ranges from zero, meaning no risk, to 10 when a collision is certain and poses mass extinction.
A space rock the size of Asteroid 2024 YR4 would not cause the end of humanity, similar to what happened 66m years ago that led to the extinction of the dinosaurs, as that was 10 to 15km wide.
However, 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.
Two UN-endorsed global asteroid response groups have been activated as the result of the detection of Asteroid 2024 YR4.
The International Asteroid Warning Network is going 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 a plan to intervene, possibly by deflecting the asteroid with an intercepting spacecraft.
Astronomers are hoping to make more detailed observations in the next few months before it fades out of view. If those measurements do not rule out an impact in 2032, the asteroid will likely 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.”