The ‘Riskiest Asteroid Ever’ Is No Longer a Threat as Impact Probability Drops to Near Zero
As astronomers predicted, asteroid 2024 YR4 is not expected to hit Earth in 2032. This week, NASA gave the “all clear”
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After about two months of high-profile uncertainty, the chance of a recently discovered asteroid hitting Earth in 2032 has dropped to a miniscule fraction of one percent.
“That’s zero folks!” says Richard Binzel, an astronomer at the Massachusetts Institute of Technology, in an email to Smithsonian magazine. NASA and the European Space Agency (ESA) announced the news this week.
The infamous asteroid 2024 YR4 was first reported by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) station in Chile on December 27, 2024. While it always had more than a 96 percent chance of harmlessly zooming past our planet, the space rock began to raise non-expert eyebrows as its impact probability increased from 1.6 percent to 2.3 percent. Then, the odds suddenly jumped to 3.1 percent—the highest ever documented by NASA for an object of this size or larger. Though the ESA’s highest assessment only reached 2.8 percent, the agency still briefly deemed it the “‘riskiest’ asteroid ever detected.”
But that’s all behind us now. One day after the space agencies announced this record, the impact probability dropped to 1.5 percent, then to 0.28 percent. As of this article’s publication, NASA’s Sentry risk table estimates a 0.0022 percent risk of impact, or a 1-in-45,000 chance. To those who had worried about the potential strike, astronomers around the world now get to say, “I told you so,” because that’s exactly what they predicted.
“I knew this was likely to go away as we collected more data,” Davide Farnocchia, a navigation engineer at NASA’s Jet Propulsion Laboratory, tells the New York Times’ Katrina Miller. “I was sleeping pretty well.”
All clear: NASA analysis drops asteroid 2024 YR4's impact probability to 0.004%, meaning it is expected to safely pass by Earth in 2032. NASA’s #PlanetaryDefense team will continue to monitor all known asteroids that may come our way.
— NASA Asteroid Watch (@AsteroidWatch) February 24, 2025
Learn more: https://t.co/h3KfDYcQoa pic.twitter.com/3Vp7EJckxv
In fact, the changing impact probability over the last several weeks has “followed a well understood pattern,” per an ESA statement. As astronomers gathered more data on the asteroid’s trajectory, they expected the impact probability to rise before eventually dropping to zero, as the region encompassing all possible orbits narrowed and no longer included Earth.
If anything, Binzel tells CNN’s Ashley Strickland that he is “pleasantly surprised that we could reduce the probability numbers so quickly.” That’s because astronomers had previously warned that, given asteroid 2024 YR4’s current trajectory away from Earth, we might have had to wait for it to fly by again in 2028 before ground telescopes could collect enough data to determine its future path in 2032.
“At the end of the day, the probability is either zero and it misses you, or it’s one and it hits you. Any number in between is just the space of your uncertainty. We didn’t want us to have to sit in that time and space of uncertainty for months and months,” Binzel adds to CNN.
Asteroid 2024 YR4 has also dropped from an attention-worthy level three to a safe level zero—for “no hazard”—on the Torino Scale, an impact risk scale developed by Binzel.
That reassessment comes “as additional tracking of its orbital path reduces its possibility of intersecting the Earth to below the 1-in-1000 threshold established for downgrading to level zero,” Binzel explains to Smithsonian magazine. He adds that 1-in-1000 is the threshold for any object smaller than around 328 feet to reach level zero, and 2024 YR4 is estimated to be approximately 164 feet. Though its impact wouldn’t have been civilization-ending, it would have caused significant local damage.
NASA and ESA astronomers will continue observing the asteroid, which, as of February 24, had a 1.7 percent chance of impacting the moon in 2032, according to NASA.
“An object the size of YR4 passes harmlessly through the Earth-moon neighborhood as frequently as a few times per year,” Binzel said in an email to Smithsonian magazine last week. “Rather than making anyone anxious, by finding these objects that are already out there and by pinning down their orbits, we are becoming more secure in our knowledge that any sizable asteroid is not likely to take us by surprise as an unwelcome guest landing on us.”
Plus, 2024 YR4 also gave the world’s space agencies a good reason to test out some of their planetary defense processes, as it engaged international asteroid response measures.
