The moon has narrowly avoided a potentially catastrophic impact from asteroid 2024 YR4, dubbed a “city-killer” due to its size and potential destructive force. New observations from the James Webb Space Telescope (JWST) have refined the asteroid’s trajectory, confirming it will pass by the moon at a distance of just 13,200 miles (21,200 kilometers) in 2032, according to a March 5 NASA statement. This close encounter, while still dramatic, eliminates the previous 4.3% chance of a lunar collision.
The asteroid, discovered in late 2024 by the Asteroid Terrestrial-impact Last Alert System (ATLAS) network, measures between 174 and 220 feet (53 to 67 meters) in diameter – roughly the size of the Leaning Tower of Pisa. Had it impacted Earth, scientists estimate it could have released energy equivalent to 500 Hiroshima bombs, earning it the moniker “city killer,” as previously reported by Live Science.
The latest observations, collected on February 18 and 26, were crucial given that, according to NASA, 2024 YR4 had become largely unobservable from Earth and other space-based observatories since spring of 2025. “Since spring of 2025, the asteroid has been unobservable from both Earth and space-based observatories except for this use of Webb,” NASA officials stated. The JWST’s sensitivity was pushed to its limits to capture these “among the faintest ever observations of an asteroid” in history. Representatives from the European Space Agency (ESA), which co-manages JWST with NASA and the Canadian Space Agency, highlighted the technical challenge: “To use one of the most complex machines humankind has ever built to track an almost invisible object many millions of kilometres away – and then accurately predict its position almost seven years into the future.”
Initially, calculations suggested a 3.1% chance of an Earth impact – the highest probability ever recorded for a potential asteroid collision. However, subsequent data from JWST and other telescopes quickly reduced that risk to zero. The focus then shifted to the lunar impact probability, which remained at 4.3% until these latest JWST observations. The asteroid will also safely miss Earth by hundreds of thousands of miles during its close approach in six years.
What Happens if an Asteroid Hits the Moon?
While the moon has been struck by asteroids throughout its history, a predicted impact of this magnitude from a known asteroid would have been unprecedented. Scientists theorized that a collision from 2024 YR4 could have been visible from Earth with the naked eye, and potentially triggered a new meteor shower due to ejected debris. Mashable notes that this event would have provided a unique opportunity to study the effects of a large impact in real-time.
Future Observations and Planetary Defense
With Earth and the moon now safe from 2024 YR4, the asteroid presents a valuable opportunity to refine planetary defense models. NASA plans to re-observe the asteroid with JWST in 2028 during its next close approach, providing further data for trajectory analysis and impact prediction. This continued monitoring will help prepare for future near-Earth object encounters.
The successful tracking and trajectory refinement of 2024 YR4 demonstrate the power of advanced telescopes like JWST in bolstering our planetary defense capabilities. Continued vigilance and investment in these technologies are crucial for mitigating the risks posed by near-Earth objects. The ability to accurately predict and potentially deflect asteroids remains a key priority for space agencies worldwide.
This incident underscores the ongoing need for robust asteroid detection and tracking programs. As technology advances, our ability to identify and characterize potentially hazardous asteroids will continue to improve, safeguarding our planet and its celestial neighbor. Share your thoughts on this near miss in the comments below.
