What was asteroid 2024 YR4, and why did its impact odds make headlines in 2025?
For about three weeks in early 2025 a 60-metre asteroid had a Torino rating of 3. Then new measurements brought it back to zero.
Guess first
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Which one is it?
2024 YR4 is an asteroid of about 60 metres across, found on 27 December 2024 by the Chilean station of the ATLAS survey. In January and February 2025 its estimated probability of hitting Earth on 22 December 2032 rose above 1%, which gave it a rating of 3 on the Torino scale from 27 January to 20 February 2025. The estimated probability peaked at 3.1% on 18 February 2025. By 23 February additional observations effectively ruled out an impact in 2032, and the rating fell to 0.
The rise set a response in motion. When the odds passed 1%, the first step in planetary defense responses was triggered, and the issued a notice on 29 January 2025. Several major telescopes took extra data, and space agencies began planning. NEODyS removed the 2032 impact chance on 1 March, ESA on 8 March and NASA on 2 April 2025.
Then the Moon made the news. As of May 2025 there was about a 4% chance of 2024 YR4 hitting the Moon on 22 December 2032. In February 2026 two further observations by the James Webb Space Telescope reduced that chance to 0%, and NASA and ESA announced it on 5 March 2026. The asteroid will safely pass about 21,200 kilometres from the Moon's surface.
A size of 60 metres matters: it is around the size of the asteroid behind the Tunguska event. Its rating of 3 reflected size and probability; it never exceeded the background risk for an asteroid of its size.
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Recap
Since March 2026, a 2032 impact of 2024 YR4 on both Earth and the Moon has been ruled out; the Earth odds rose to 3.1% and then fell.
๐ก A trick to remember it ยท A spotlight on a dot: odds climbed for three weeks, then more measurements switched the spotlight off.
Surprising fact ยท A 4% chance of hitting the Moon in 2032 stood for almost a year, until two JWST observations in February 2026 reduced it to 0%.
Connects to
- ๐ฏ What did NASA's DART mission show when it crashed into an asteroid?
- ๐ What is the Torino scale, and why do asteroid impact odds rise and then fall?
- ๐ฅ What was the Tunguska explosion of 1908, and how did Chelyabinsk in 2013 compare?
- ๐ Will asteroid Apophis hit Earth, and what happens at its 2029 flyby?
- ๐ Why does the James Webb telescope hide behind a sunshield 1.5 million km from Earth?
- Planetary defense
Sources (1)
No source, no claim. Every fact in this lesson (15 claims) cites at least one of these.