JWST Data Rules Out Moon Impact from ‘City-Killer’ Asteroid in 2032

The moon is officially in the clear from a potential impact by asteroid 2024 YR4, initially dubbed a “city-killer,” thanks to refined observations from the James Webb Space Telescope (JWST). What was once a 4.3% chance of a lunar collision has now been reduced to zero, NASA announced on March 5, 2026. This news follows a period of concern sparked by the asteroid’s discovery in late 2024 and subsequent trajectory calculations.

The latest data, collected on February 18 and 26, utilized JWST’s sensitive infrared instruments to pinpoint the asteroid’s path with unprecedented accuracy. Astronomers were able to refine previous estimates, revealing that 2024 YR4 will now pass within a relatively close, but ultimately safe, 13,200 miles (21,200 kilometers) of the lunar surface in December 2032 – closer than some artificial satellites orbit Earth. The asteroid will also safely miss Earth by hundreds of thousands of miles during its return swing through the inner solar system six years from now.

A Test of Planetary Defense Capabilities

Asteroid 2024 YR4, measuring between 174 and 220 feet (53 to 67 meters) in diameter, initially raised alarms due to its size and potential for significant damage should it impact a populated area on Earth. An impact of this magnitude could release energy equivalent to 500 Hiroshima bombs, according to previous Live Science reporting. While an Earth impact was quickly ruled out, the possibility of a lunar collision remained a concern, making 2024 YR4 the most closely monitored asteroid in two decades.

The successful refinement of the asteroid’s trajectory underscores the critical role of advanced telescopes like JWST in planetary defense. As NASA officials stated, these observations represent some of the faintest ever recorded of an asteroid, pushing the telescope to its operational limits. The ability to track such faint objects at vast distances is crucial for identifying and characterizing potentially hazardous near-Earth objects (NEOs).

The Challenge of Faint Object Tracking

Detecting and tracking asteroids like 2024 YR4 isn’t easy. After initially being observed in the spring of 2025, the asteroid faded from view, making it difficult to pinpoint its location until the recent JWST observations. Astronomers seized two narrow windows in February 2026, leveraging the precision of the European Space Agency’s (ESA) Gaia mission, which provides highly accurate positional data for stars, to locate the faint asteroid against a sparse stellar backdrop.

JWST was originally designed to study distant galaxies, making the task of observing a relatively small and faint asteroid even more challenging. Its small field of view required extraordinary precision and careful planning, coordinated between ESA’s Near-Earth Object Coordination Centre, NASA’s Center for Near-Earth Object Studies, and the Webb mission team. This collaborative effort highlights the international commitment to planetary defense.

What Does This Mean for Lunar and Earth Safety?

The elimination of the lunar impact risk is a significant relief, but the story of 2024 YR4 offers valuable lessons for future planetary defense efforts. The asteroid served as a real-world test case for assessing and refining models used to predict the trajectories of NEOs. The data gathered from JWST observations will help improve our understanding of asteroid behavior and enhance our ability to respond to potential threats.

While 2024 YR4 no longer poses an immediate danger, it will remain a target for astronomers. NASA plans to re-observe the asteroid with JWST in 2028 as it returns to the inner solar system, providing another opportunity to validate planetary defense models and gather additional data. This continued monitoring will contribute to a more comprehensive understanding of the NEO population and improve our preparedness for future close encounters.

Understanding Asteroid Risk and Planetary Defense

It’s important to understand that the risk posed by NEOs is constantly being assessed and refined. The initial 3.1% probability of an Earth impact from 2024 YR4, while the highest ever recorded, was still relatively low. However, it underscored the importance of continued vigilance and investment in planetary defense technologies.

Planetary defense strategies include:

• Detection and Tracking: Identifying and cataloging NEOs, particularly those that reach close to Earth.
• Trajectory Prediction: Accurately calculating the orbits of NEOs to assess potential impact risks.
• Mitigation Techniques: Developing methods to deflect or disrupt asteroids that pose a credible threat (though these are still largely theoretical).

The success of the JWST observations in refining the trajectory of 2024 YR4 demonstrates the power of advanced technology in mitigating the risks posed by NEOs. Continued investment in these capabilities is essential for protecting our planet and ensuring the long-term safety of humanity.

Looking Ahead: Continued Surveillance and Model Refinement

The story of asteroid 2024 YR4 isn’t over. The data collected during this close encounter will be invaluable for refining planetary defense models and improving our ability to predict and respond to future threats. Continued surveillance of NEOs, coupled with advancements in telescope technology and trajectory prediction algorithms, will be crucial for safeguarding Earth and its moon from potential impacts. The focus now shifts to analyzing the JWST data and incorporating it into existing planetary defense frameworks, ensuring we are better prepared for the next asteroid that comes our way.