Undoubtedly one of the biggest space science stories of 2025 was the news of asteroid 2024 YR4 which, for a brief period at least, looked like it might hit Earth.
And while the chance of it hitting our planet was eventually ruled out, there remained a small possibility that it might hit our Moon instead.
But observations by the James Webb Space Telescope in February 2026 have led scientists to rule out asteroid 2024 YR4 hitting our Moon.
The story of YR4
When the story of asteroid 2024 YR4 broke, the probability of it hitting Earth rose from 1.2% to 2.3%, then to 2.6%, peaking at 3.1% on 18 February 2025.
However, when astronomers are observing a potential asteroid threat, they’re able to refine its predicted trajectory as they gather more information.
The risk of 2024 YR4 hitting Earth fell to 1.5% on 19 February 2025 and, on 20 February, dropped dramatically to 0.28%.
By 23 February 2025, the chance of 2024 YR4 hitting Earth fell to 0.0050%.
By April 2025, the asteroid had disappeared from view as it travelled away from Earth on its orbit around the Sun.
However, 2024 YR4 is due to return near Earth in 2028, and the question remained as to whether it might hit our Moon.
A science paper released early in 2026 even looked into what would happen if 2024 YR4 hit our Moon.
International Gemini Observatory/NOIRLab/NSF/AURA/M. Zamani
Eliminating the lunar risk
As asteroid 2024 YR4 faded from view in 2025, scientists still couldn’t completely rule out the chance of it hitting our Moon.
They had even nailed down a date – 22 December 2032 – as to when the collision would occur, if it were to happen.
And while the chances of 2024 YR4 hitting our Moon remained low at 4%, that was still enough to cause concern among the planetary defence scientific community.
Scientists now say the risk of 2024 YR4 hitting our Moon has been eliminated.
The confirmation came following observations using the Near-Infrared Camera (NIRCam) on the James Webb Space Telescope.
According to the data, the asteroid will pass the Moon at a distance of more than 20,000km (12,400 miles).
How Webb saw 2024 YR4
Scientists say that, while asteroid 2024 YR4 was not expected to be visible again until 2028, they were able to identify two slim chances of spotting it with the James Webb Space Telescope in February 2026.
This was thanks to the work of the European Space Agency’s Gaia mission, which mapped about 2 billion stars in our Galaxy.
That meant scientists effectively had a starmap of the Milky Way they could use to detect 2024 YR4.
But even still, this meant tracking a tiny object millions of km away and using the observations to predict its orbit seven years into the future.
The data was analysed by ESA’s Near-Earth Object Coordination Centre, NASA’s Center for Near-Earth Object Studies and Webb scientists.
The two images here show how Webb was able to pick-out 2024 YR4 moving against the backround stars
The science team say that, by comparing 2024 YR4’s position, they could measure its orbit accurately and rule out a lunar impact in 2032.