The Scenario
It is December 22, 2032. Asteroid 2024 YR4, a rocky body roughly 60 metres across, is hurtling through space at approximately 8 kilometres per second relative to the Moon. The 4.3% probability has come true. Impact is seconds away.
What happens next?
The Energy of Impact
When a 60-metre asteroid strikes a surface at several kilometres per second, the kinetic energy release is staggering. Estimates put the impact energy of 2024 YR4 at roughly 7 megatons of TNT equivalent — about 500 times the energy of the Hiroshima bomb.
On Earth, an explosion of this magnitude would be devastating for a regional area. On the Moon, with no atmosphere to create a shockwave, all that energy goes directly into the surface.
The Crater
The impact would excavate a crater roughly 1 kilometre in diameter on the lunar surface. To put that in perspective, the Moon already has thousands of craters this size and larger — but none that humans have ever witnessed being formed.
The ejecta — rock and dust blasted out of the crater — would be thrown high above the lunar surface. In the Moon's low gravity (about one-sixth of Earth's), this material would arc outward for considerable distances. Some of the fastest ejecta could escape the Moon's gravity entirely.
What Would You See from Earth?
The impact flash would likely be visible to the naked eye for observers on the night side of Earth where the Moon is visible. The flash would last only a fraction of a second, but it would be unmistakable.
Telescopes and cameras pointed at the Moon would capture a bright point of light at the impact site, followed by a slowly expanding dust cloud. The Lunar Reconnaissance Orbiter, if still operational, could potentially image the fresh crater within hours.
The event would be recorded by every astronomical instrument capable of observing the Moon — making it the most documented impact event in human history.
Could Debris Reach Earth?
This is the question everyone asks. The short answer: it is theoretically possible but extremely unlikely.
For ejecta to reach Earth, it would need to escape the Moon's gravity (about 2.4 km/s escape velocity) and then be on a trajectory that intersects Earth's orbit. While some fraction of high-velocity ejecta could achieve this, the material would be small fragments — sand and pebble-sized — not large rocks.
Any such debris entering Earth's atmosphere would almost certainly burn up harmlessly as meteors. You might, weeks or months later, see an unusual burst of "shooting stars" — a brief, artificial meteor shower from lunar material.
Effects on the Moon
Beyond the crater itself, the impact would:
- Generate seismic waves through the lunar interior, detectable by any seismometers on the surface
- Kick up a temporary dust atmosphere that would settle over hours or days
- Expose fresh subsurface material of scientific interest
The Moon has no atmosphere, no water, and no life. A 1-kilometre crater is geologically insignificant — the Moon bears the scars of billions of years of bombardment far more intense than one 60-metre asteroid.
Scientific Value
Paradoxically, a lunar impact would be a scientific goldmine:
- Real-time cratering physics: We have never observed a crater of this scale being formed. The data would revolutionise our understanding of impact mechanics.
- Lunar interior studies: The seismic energy would probe the Moon's internal structure more effectively than any instrument we could place there.
- Ejecta analysis: Spectroscopic observations of the ejecta plume would reveal the composition of the subsurface material at the impact site.
- Calibration data: Every model of asteroid impacts — including those predicting what would happen if a similar object hit Earth — would be tested against real observations.
What It Would Not Do
A lunar impact by 2024 YR4 would not:
- Alter the Moon's orbit in any measurable way (the Moon is far too massive)
- Affect tides on Earth
- Send dangerous debris to Earth's surface
- Pose any threat to astronauts in Earth orbit
- Be visible during the daytime from Earth
The Bigger Picture
Whether or not 2024 YR4 hits the Moon, its story highlights why planetary defence matters. The same detection systems that found this asteroid and calculated its trajectory are the ones protecting Earth from far more dangerous scenarios.
A Moon impact, while dramatic, would ultimately be a reminder that we live in a dynamic solar system — and that the tools we have built to watch the skies are working as intended.
This article presents a hypothetical scenario based on current orbital data. The probability of impact is approximately 4.3%. Data sourced from NASA/JPL and ESA NEOCC.