NASA doubles risk of 'city-killer' asteroid smashing into Moon in major update (2025)

Asteroid 2024 YR4 is the size of a 10-story building and could collide with the Moon in 2032

NASA scientists have revealed that the infamous "city-killer" asteroid that once posed a threat to Earth could now smash into the Moon.

In February, astronomers revealed that asteroid 2024 YR4 had a 3.1 per cent – or one-in-32- chance – of striking Earth on December 22, 2032.

The space rock once posed the greatest risk of impact to Earth in recorded history, but NASA downgraded the odds of impact to near-zero just days later, stating that the asteroid is no longer a threat and is expected to "safely pass Earth".

Now, NASA's James Webb Space Telescope has revealed that impact is still a possibility – but with the Moon instead.

The space telescope, which took an emergency look at the asteroid on March 26, confirmed that the space rock is no longer a hazard to Earth, with a zero chance the asteroid could smash into our home planet.

However, NASA revealed that new data collected by the space telescope suggest a 3.8 per cent chance of a moon strike, up from a 1.8 per cent chance back in February, meaning the odds of a lunar impact have more than doubled.

NASA's space telescope has also revealed that asteroid 2024 YR4 is slightly bigger than previously thought. NASA now says the asteroid is somewhere between 174 to 220 feet (53 to 67 metres) in diameter, or about the size of a 10-story building. Previous estimations said the space rock was between 131 and 295 feet (40 and 90 metres).

The current size estimations were based on infrared observations by the Webb telescope, whereas the previous estimate was derived from visible light measurements from ground-based telescopes, NASA says.

But what would happen if asteroid 2024 YR4 did smash into the Moon?

NASA wrote in a blog post: "There is still a 96.2 per cent chance that the asteroid will miss the Moon. In the small chance that the asteroid were to impact, it would not alter the Moon’s orbit."

In theory, if a large enough object smashed into the lunar surface, it could "break up" the Moon, according to one NASA scientist.

"I think the only plausible astronomical event that could untether the Moon would be a large impact to the Moon that breaks it up," said Noah Petro, project scientist for NASA's Artemis 3 Moon mission.

"Similar to the large impact that is thought to have led to the formation of the Moon, a large enough object could, in theory, break the Moon apart," Petro told Space.com.

However, asteroid 2024 YR4 is far too small to cause such catastrophic damage, so we can rest assured that the Moon won't suddenly disappear from the night sky in 2032.

The European Space Agency (ESA) said in a video: "If that [impact] happens, there won't be any shockwaves felt on Earth and the Moon won't crack in half.

"But it would leave a brand-new crater, and if we're lucky, we might catch the exact moment it happens."

As astronomers gather more data about the asteroid's trajectory, the probability of impact could fluctuate before ultimately reaching zero, as we observed with Earth.

Further observations by the James Webb Space Telescope are planned for May 2025, before the asteroid disappears from view until 2028.