The Discovery
Asteroid 2024 YR4 was discovered on December 27, 2024, by the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey — a NASA-funded early warning system based in Hawaii and South Africa that scans the entire sky every 24 hours.
Within days of its discovery, orbital calculations revealed something unusual: this small space rock had a statistically significant probability of striking the Moon in 2032. That probability — roughly 4.3% — makes it the most closely watched near-Earth object in recent history.
How Big Is It?
At approximately 60 metres in diameter, 2024 YR4 is modest by asteroid standards. For comparison, the asteroid that created Meteor Crater in Arizona was about 50 metres across, while the one that ended the dinosaurs was roughly 10 kilometres wide.
Still, 60 metres is nothing to dismiss. An object this size travelling at tens of kilometres per second carries enormous kinetic energy — estimated at around 7 megatons of TNT equivalent if it were to strike a solid surface.
The Orbit
2024 YR4 is classified as an Apollo-type asteroid, meaning its orbit crosses Earth's orbit around the Sun. It completes one trip around the Sun in roughly 3.5 years and has a moderately inclined, slightly elliptical orbit.
What makes the December 2032 close approach special is the geometry: the asteroid's predicted path passes through a region of space where the Moon will also be at that time. The uncertainty in the asteroid's exact trajectory is what gives rise to the impact probability.
The 2032 Close Approach
The critical date is December 22, 2032, when 2024 YR4 will make its closest approach. Current calculations put the lunar impact probability at roughly 4.3% and the Earth impact probability at 0%.
If it does hit the Moon, it would be the most energetic lunar impact ever witnessed by humanity — a flash visible to observers on Earth, potentially creating a crater roughly 1 kilometre across.
If it misses the Moon (the 95.7% scenario), the asteroid will continue on its orbit and return for future close approaches. Each observation window gives astronomers more data to refine the orbit.
Why Does This Matter?
Even though the chance of impact is relatively small, 2024 YR4 represents a landmark case in planetary science:
- It tests our detection systems. The fact that we found this object and calculated its trajectory demonstrates that our asteroid warning infrastructure works.
- It raises questions about lunar impacts. We have spent decades worrying about Earth impacts, but a Moon strike would have scientific implications we are only beginning to explore.
- It engages the public. This is a tangible, real scenario playing out over several years — a slow-motion cosmic event that anyone can follow.
How Are Scientists Tracking It?
Multiple facilities around the world are observing 2024 YR4, including:
- NASA's Center for Near-Earth Object Studies (CNEOS) at the Jet Propulsion Laboratory
- ESA's Near-Earth Object Coordination Centre (NEOCC) in Italy
- Ground-based observatories contributing astrometric data to the Minor Planet Center
Each new observation slightly refines the orbit, which in turn adjusts the impact probability up or down. Over the next few years, the probability will converge toward either 0% (a definitive miss) or a higher confidence of impact.
What Happens Next?
As 2024 YR4 continues orbiting the Sun, there will be periodic observation windows when it is visible from Earth. Each window provides fresh data.
By the late 2020s, astronomers expect to have enough observations to determine the outcome with high confidence. Until then, 2024 YR4 remains one of the most fascinating objects in our cosmic neighbourhood.
Data sourced from NASA/JPL Small-Body Database and ESA NEOCC. Last updated February 2025.