Asteroid 2024 YR4, which was once deemed the highest impact risk to Earth ever recorded, has recently returned to scientific discussions. This time, the spotlight is on a slight increase in the likelihood that this asteroid could collide with the moon in 2032. Observations made by the James Webb Space Telescope (JWST) in May have provided new insights into the asteroid's trajectory.
A team of researchers, led by Andy Rivkin from the Johns Hopkins Applied Physics Laboratory, utilized data from the JWST's Near-Infrared Camera to refine the predictions regarding where 2024 YR4 will be on December 22, 2032. Their efforts improved the accuracy of the asteroid's predicted path by nearly 20%, resulting in an increase in the odds of a lunar impact from 3.8% to 4.3%, as reported by NASA.
The statement from NASA emphasized that as new data emerges, it is typical for the impact probabilities to evolve. Even if a collision were to occur, experts assert that it would not have any significant effect on the moon's orbit. According to astronomer Pawan Kumar, a former researcher at the Indian Institute of Astrophysics in Bengaluru, there is no cause for concern. He explains that if the moon were to experience a collision, any debris generated would likely burn up in Earth's atmosphere before reaching near-Earth space.
First detected on December 27, 2022, 2024 YR4 is estimated to measure between 174 to 220 feet long (53 to 67 meters), roughly the size of a 10-story building. Initially, the asteroid garnered widespread attention due to its over 1% chance of hitting Earth, representing the highest recorded risk for any large asteroid. Subsequent observations in January and February revealed that the impact risk had surged from 1.2% to a peak of 3.1%.
At that time, the asteroid's projected trajectory indicated it could potentially cause damage across a vast impact zone, stretching from the eastern Pacific to northern South America, Africa, and southern Asia. NASA estimated that if it were to enter Earth's atmosphere over the ocean, significant tsunamis would be unlikely. However, an airburst over a populated city could result in shattered windows and minor structural damage.
Fortunately, as more orbital data was collected, the impact risk for 2024 YR4 dropped significantly. By February 19, the probability had decreased to 1.5%, and further analysis the following day brought it down to 0.3%. On February 24, NASA declared an official "all clear" via social media, revealing that the impact probability had plummeted to just 0.004%, indicating that the asteroid is expected to pass safely by Earth in 2032.
Further investigations have confirmed that there is no risk to Earth from 2024 YR4 during its upcoming close approaches, including the one in 2032. Recent data from telescopes located in Chile and Hawaii suggests that the asteroid originated from the central main belt between Mars and Jupiter before gradually shifting into a near-Earth orbit.
Since mid-April, 2024 YR4 has been too distant and faint to be observed from Earth. It is anticipated to come back into view in 2028, providing scientists with another opportunity to observe the asteroid. Researchers will utilize both the JWST and ground-based telescopes to gather further data on its shape and composition—essential factors for understanding its behavior and potential impact effects.
While 2024 YR4 no longer poses any immediate danger, this asteroid has offered scientists a unique, real-world opportunity to test the full range of planetary defense strategies. This includes everything from initial detection and risk assessment to public communication. As Kumar stated, “It was an actual end-to-end exercise for how we might respond to a potentially hazardous asteroid in the future.” He added that 2024 YR4 is a model asteroid for planetary defense efforts, possessing all the characteristics necessary to capture our attention.
