‘City-killer’ asteroid could strike Moon, missing Earth: scientists

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A so-called “city-killer” asteroid once feared to be on a collision course with Earth could instead crash into the Moon, according to updated observations by NASA scientists.

Asteroid 2024 YR4, discovered last year, initially raised concerns with a projected 3% chance of striking Earth in December 2032.

A collision of that magnitude could devastate areas up to 80 kilometres from the impact site.

Further tracking and analysis have since ruled out an Earth impact, bringing the threat level down to near zero.

However, new data from NASA’s James Webb Space Telescope has placed the odds of a Moon impact at nearly 4%.

“At this writing, a 2032 impact with the Moon has not been ruled out,” wrote lead author Andy Rivkin of Johns Hopkins University in a study published in the Research Notes of the AAS journal.

NASA noted that while the probability remains low, at over 96% chance of a miss, the scenario remains under observation. The next potential opportunity for close tracking will be in early 2026, researchers said.

The revised estimate also updated the asteroid’s size to between 53 and 67 metres—roughly equivalent to a 15-storey building—underscoring the potential scale of a lunar impact.

Scientists say even a 1% chance of Earth impact would justify planning asteroid deflection missions. The current focus, however, is on using any Moon impact to refine planetary defence strategies.

“The possibility of getting a chance for an observation of a sizable Moon impact is indeed an interesting scenario from a scientific point of view,” said Richard Moissl, head of the European Space Agency's planetary defence office.

Researchers believe such an impact could offer valuable data, helping scientists better prepare for future asteroid threats.

NASA expects more potential impactors to be identified as advanced asteroid-tracking systems come online in the coming years.