NASA has identified an asteroid known as 2024 YR4 with a 3.1 percent chance of impacting Earth on Dec. 22, 2032. While this probability is still relatively low, it is the highest recorded risk of any known asteroid in modern history.
Asteroid 2024 YR4 is classified as a three on the Torino Scale, a system that assesses the risk posed by near-Earth objects on a scale from zero to ten. NASA has noted that it is uncommon for an asteroid to be rated at Torino Scale 3, as such ratings require a significant size and an impact probability of at least one percent.
Discovered on Dec. 27, 2024 by NASA’s Asteroid Terrestrial-impact Last Alert System in Chile, Asteroid 2024 YR4 quickly caught attention when it was placed on NASA’s Sentry risk list on Dec. 31. The Sentry risk list tracks objects with a non-zero probability of impact, but historically, asteroids have been placed on this list only to be reassigned to a zero-impact probability as more data becomes available.
Head of the European Space Agency’s Planetary Defense Office Richard Moissl called the situation “historic” but reassured the public that this is not an existential threat.
“This is not the dinosaur killer. This is not the planet killer. This is at most dangerous for a city,” Moissl said. “If an impact were to occur, the Asteroid’s speed could lead to an airburst explosion with a force of about eight megatons of TNT – over 500 times the power of the Hiroshima bomb.”
Experts have emphasized that such initial impact probabilities tend to decrease over time as astronomers gather more precise data. NASA’s James Webb Space Telescope is set to observe 2024 YR4 in March 2025 and May 2025, providing more clarity on its trajectory. If the probability of impact rises about 10 percent, the International Asteroid Warning Network will issue a formal warning, advising UN members with potentially affected regions to begin preparedness measures.
Current impact risk corridors suggest that regions spanning the eastern Pacific, South America, the Atlantic, Africa, the Arabian Peninsula, and South Asia are potential target zones. This includes major cities such as Bogotá, Mumbai, Chennai, and Lagos.
The International Asteroid Warning Network issued a formal warning on Jan. 29 when the impact probability exceeded one percent, but experts stress that there is still ample time for intervention if necessary. While NASA’s 2022 Double Asteroid Redirection Test mission demonstrated that spacecraft could successfully alter an asteroid’s trajectory, this method is most effective for small to medium-sized asteroids with long lead times before impact.
DART was originally tested on the moonlet Dimorphos, which measured about 525 feet in diameter. Altering the path of an asteroid like 2024 YR4, which is smaller than Dimorphos, would depend on multiple factors, including mass, composition, and velocity.
Other proposed planetary defense methods include using gravity tractors, lasers, or nuclear detonations as a last resort. If necessary, such mitigation efforts would likely need to be tested and refined before any real-world application.
For now, scientists are closely monitoring 2024 YR4’s orbit with further assessments planned through April and again in June 2028 when it approaches Earth’s vicinity. As planetary scientist Bruce Betts optimistically stated, “The odds are very good that not only will this not hit Earth, but at some point, in the next months to few years, that probability will go to zero.”
