Observations from the James Webb Space Telescope have ruled out any possibility that asteroid 2024 YR4 will impact the Moon on December 22, 2032. According to NASA’s Center for Near-Earth Object Studies, the conclusion follows the analysis of data collected by the telescope on February 18 and 26. Instead of a collision, the asteroid will pass the Moon at a distance exceeding 20,000 km.
Precision Tracking of a Faint Object
The confirmation was the result of a collaboration between the Webb mission, NASA’s Center for Near-Earth Object Studies, and ESA’s Near-Earth Object Coordination Centre. Astronomers used the telescope’s Near-Infrared Camera (NIRCam) to detect the 60-meter-wide near-Earth object during two narrow windows in February 2026. This effort was necessary because the asteroid had faded from view the previous spring and was not expected to be visible again until 2028.
Tracking the object required extraordinary precision due to the telescope’s small field of view and the asteroid’s faintness. To accurately predict the orbit seven years into the future, the international team compared the position of 2024 YR4 against background stars, whose positions were previously established by ESA’s Gaia mission.
The Initial Earth Impact Warning
While the Moon is now confirmed safe, 2024 YR4 previously triggered the first formal asteroid notification issued through an international planetary-defence system. The International Asteroid Warning Network (IAWN) sent a formal notice to the Space Mission Planning Advisory Group and the United Nations Office for Outer Space Affairs on January 29, 2025.
This notification was triggered after three independent orbit-computation centres—NASA CNEOS, ESA’s Near-Earth Object Coordination Centre, and the NEO Dynamic Site in Italy—agreed on January 27, 2025, that the chance of an Earth impact had exceeded 1 per cent. Specifically, the estimate was 1.3 per cent, meaning there remained a 98.7 per cent chance of a miss. The asteroid reached level 3 on the Torino Scale, a rating that necessitates attention from public officials for encounters occurring in less than a decade.
The initial uncertainty stemmed from a short observation arc. The NASA-funded Asteroid Terrestrial-impact Last Alert System discovered the object at its Río Hurtado, Chile station on December 27, 2024, two days after it had passed close to Earth. Pre-discovery images only extended the record back to December 25, forcing astronomers to project a short segment of the orbit eight years forward to 2032.
Projected Effects of a Lunar Impact
Before the James Webb Space Telescope eliminated the risk, researchers had focused on the potential aftermath of a lunar collision. Earlier calculations suggested a 4% to 4.3% chance of the asteroid striking the Moon. A preprint published in Astrophysics modeled these effects, noting that the 60-meter rock would have hit at a velocity of approximately 14 kilometers per second.
The modeled impact would have resulted in the following:
- Energy Release: An explosion equivalent to about 6.5 million tons of TNT.
- Crater Size: A crater roughly one kilometer across, which would have been the most energetic lunar impact recorded in the era of modern observation.
- Seismic Activity: A moonquake with a magnitude of about 5.
- Debris: Depending on the impact angle, tens to hundreds of millions of kilograms of rock could have escaped the Moon’s gravity.
International Planetary Defence Protocols
The response to 2024 YR4 demonstrated a system endorsed by United Nations bodies in 2013. The protocol dictates that once numerical and size criteria are met, notifications are issued regardless of whether a single agency finds the situation alarming. The immediate response to the 2024 YR4 warning was to prioritize observations and refine the orbit rather than automatically authorizing a spacecraft mission.
ESA’s Space Safety Programme continues to track near-Earth objects to ensure that genuine dangers are detected in time to avoid being caught unaware.
