The chances of asteroid 2024 YR4 impacting Earth have risen, with astronomers increasing the odds from 1.3% to 2.3% that it will strike Earth on Dec. 22, 2032.
The asteroid, which is thought to measure about a third of a mile (half a kilometer) in diameter, is slightly larger than Disneyland in California, which measures a quarter of a square mile. It currently sits atop the Sentry list of objects whose orbital trajectories suggest a possible impact with Earth in the future. That list is kept by the Center for Near Earth Object Studies at NASA's Jet Propulsion Laboratory, which recently refined 2024 YR4's chance of striking Earth.
Its "risk corridor" has been calculated to be across the eastern Pacific Ocean, northern South America, the Atlantic Ocean, Africa, the Arabian Sea, and South Asia, according to the International Asteroid Warning Network, which NASA chairs, IAWN released a warning about 2024 YR4 last week.
If it did strike Earth, 2024 YR4 would cause "severe blast damage," according to IAWN, up to 31 miles (50 kilometers) from the impact site.
The jump from 1.3% to 2.3 represents a once-in-77 chance, increasing to a 1-in-43 chance. That may not seem high, but others suggest there's an even greater chance of an impact. Sam Deen, a California-based amateur astronomer, calculates that there could be a 6% chance that asteroid 2024 YR4 could strike Earth, reports Sky and Telescope. That's just a one-in-17 chance.
2024 YR4 now has a value of 3 on the Torino Impact Hazard Scale, the International Astronomical Union's list of asteroids that come close to Earth. That puts it way out in front of any other asteroid.
If 2024 YR4 were confirmed to be on a collision course, there would likely still be time for a mission to deflect it. "Early action would be crucial, as later interventions become significantly more difficult," said Dr. Shyam Balaji, a researcher in astroparticle physics and cosmology at King's College London, in an email. If a deflection mission was planned, there are three ways to do it -- a kinetic impactor to change its course (as NASA successfully did in 2022 with its DART mission), a gravity tractor (a spacecraft pulling the asteroid off course) or a nuclear deflection.
It's important to put 2024 YR4 in context. "More than 33,000 near-Earth asteroids have been discovered and tracked since 1990 -- so asteroid 2024 Y24 is one of many being observed," said Balaji. "At present, the public should not be overly concerned, though the asteroid warrants continued monitoring." More data and analysis are needed to confirm the asteroid's size and refine its trajectory, which is likely to rule out any chance of impact. However, 2024 YR4 will only be visible from Earth until April 2025, remaining out of sight until June 2028, just 4.5 years before a possible impact. Worse, radar observations won't be possible until 2032, just months before it could strike Earth.
Most objects initially flagged as risks eventually become non-threats. "Historically, most asteroids with initial impact probabilities have seen their risk drop to zero as more data is collected," said Balaji. "However, uncertainties remain, and ongoing observations are essential to refine its trajectory." He stressed the importance of astronomers gathering as much data as possible about 2024 YR4 before it becomes unobservable.
2024 YR4 was discovered on Dec. 27, 2024, by the Asteroid Terrestrial-impact Last Alert System, an asteroid impact early warning system developed by the University of Hawaii in Río Hurtado, Chile and funded by NASA.