In the spring of 2024, the Moon received a visitor it could not refuse — a comet or asteroid the size of a small building, striking at full velocity to carve a fresh wound 222 meters wide into a surface already ancient with scars. Named McGetchin after its formal identification this year by NASA researcher Robert Wagner, the crater stands as the largest impact event ever documented in near-real time anywhere in the solar system. Its discovery reminds us that the cosmos is not finished with us, nor with the worlds we are preparing to visit — and that patience, not spectacle, is often the instru
NASA discovers largest newly-formed lunar crater from rare spring 2024 impact
The Moon has no such protection.
Mark
So a building-sized rock hit the Moon in spring 2024, and we're only finding out about it now?
Mimi
Yes. The crater formed then, but it took until this year for a NASA researcher reviewing orbital images to spot it. The Lunar Reconnaissance Orbiter has been mapping the Moon since 2009, so the data was being collected all along—it just took human eyes to recognize what they were seeing.
Luke
How certain are we about the spring 2024 date? Is that based on direct observation or inference from the crater's appearance?
Mimi
It's inferred from the crater's freshness—the bright material and dark halo around it indicate a recent impact. The researchers can see it's new, but the exact date is an estimate based on how fresh the features look.
Mark
Why does it matter that we're studying this crater now, rather than waiting for the next one?
Mimi
Because McGetchin is fresh enough that we can observe the impact's immediate effects on the lunar surface. Older craters have been weathered by radiation and micrometeorite bombardment. This one still shows us how the Moon's geology responds to a major collision.
Luke
The source says impacts of this size happen once a century or longer. That's a wide range. Do we actually know which?
Mimi
The source gives it as "once in a century or even longer," so it's genuinely uncertain. It's rare enough that we don't have a tight statistical picture.
Mark
And this matters for the crewed missions coming up?
Mimi
Directly. If astronauts are going to land on the Moon, they need to understand the terrain, the stability of different regions, and what hazards exist. A fresh crater teaches us about those processes in ways that ancient craters cannot.
Luke
Is McGetchin in a location where future missions are planned, or is this more general knowledge-building?
Mimi
The source doesn't specify McGetchin's location relative to planned landing sites. It's framed as general knowledge that will inform mission planning, not as a specific hazard at a specific site.
The Pulse
- A comet or asteroid the size of a three-to-six-story building slammed into the Moon in spring 2024, carving a 730-foot crater that went unnoticed for over a year until a NASA researcher spotted it in orbital imagery.
- The crater, named McGetchin, is now confirmed as the largest newly formed impact site ever documented in the solar system — a once-per-century event that scientists were fortunate to catch while its features are still fresh.
- Unlike Earth, the Moon has no atmosphere to slow or burn up incoming debris, meaning every rock and comet fragment arrives at full destructive speed — making the lunar surface a live record of cosmic violence.
- Scientists are racing to study McGetchin's sharp walls, bright ejecta, and undisturbed debris field before lunar weathering erases the fine details that older craters can no longer provide.
- The discovery carries urgent practical stakes: both NASA and China are developing crewed lunar missions, and understanding how impacts reshape the surface is essential for identifying safe landing zones and protecting future astronauts.
In the spring of 2024, the Moon received a visitor it could not refuse — a comet or asteroid the size of a small building, striking at full velocity to carve a fresh wound 222 meters wide into a surface already ancient with scars. Named McGetchin after its formal identification this year by NASA researcher Robert Wagner, the crater stands as the largest impact event ever documented in near-real time anywhere in the solar system. Its discovery reminds us that the cosmos is not finished with us, nor with the worlds we are preparing to visit — and that patience, not spectacle, is often the instrument through which science reveals its most consequential truths.
In the spring of 2024, a comet or asteroid roughly the size of a three-to-six-story building struck the Moon at full speed, carving a crater 730 feet wide into its ancient surface. No one noticed immediately. It was not until this year that NASA researcher Robert Wagner, reviewing imagery from the Lunar Reconnaissance Orbiter, formally identified and named the site McGetchin. A study published in Science Advances has since confirmed it as the largest newly discovered crater anywhere in the solar system.
McGetchin appeared in orbital scans as a bright spot ringed by a dark halo — the signature of a fresh impact, where the collision exposed new material and scattered debris across the surrounding terrain. What makes the discovery remarkable is not the crater's size relative to the Moon's ancient giants, but the fact that scientists caught it forming in near-real time. Impacts of this magnitude are estimated to occur on the Moon only once per century or longer.
Because the Moon has no atmosphere, incoming objects face no friction, no heat, no resistance — they arrive intact and at full velocity. This makes the lunar surface a continuous, unfiltered record of cosmic bombardment, and McGetchin's fresh features offer a rare window into the mechanics of impact geology that older, weathered craters cannot.
The timing matters beyond pure science. With both the United States and China developing crewed lunar missions, understanding how the Moon's surface responds to impacts — what regions are stable, what hazards exist — is essential preparation. Wagner's discovery came through quiet, routine analysis of orbital data, the kind of patient work that rarely makes headlines but steadily builds the knowledge on which human exploration depends. The Moon, it turns out, is still being written.
In the spring of 2024, something struck the Moon. A comet or asteroid, roughly the size of a three-to-six-story building, collided with the lunar surface at speed. The impact carved out a crater 730 feet across—222 meters of fresh scar tissue on a world that has been collecting such wounds for billions of years. But no one noticed right away. It took until this year, when a NASA researcher named Robert Wagner was reviewing fresh orbital imagery, for the crater to be formally identified and named McGetchin.
Wagner works with the Lunar Reconnaissance Orbiter, a spacecraft that has been mapping the Moon's surface since 2009. In the new scans, McGetchin appeared as a bright spot ringed by a darker halo—the telltale signature of a recent impact, where the collision has exposed fresh material and scattered debris across the surrounding terrain. The discovery is significant not because McGetchin is the Moon's largest crater. It isn't. The Moon is pocked with craters far larger, some hundreds of kilometers wide, relics of the solar system's violent youth. What makes McGetchin remarkable is that it is the largest crater scientists have ever documented forming in real time, or close to it. A study published this week in Science Advances confirmed it as the largest newly discovered crater anywhere in the solar system.
Impacts of this scale are rare. NASA estimates that an event of McGetchin's magnitude occurs on the Moon roughly once every century, perhaps longer. The Moon's lack of atmosphere means there is no friction to slow incoming objects, no heat to burn them up before they strike. Every piece of space debris that reaches the lunar surface arrives at full velocity. On Earth, our thick air acts as a shield, burning up most small asteroids and comets before they can do damage. The Moon has no such protection.
For lunar scientists, the timing of McGetchin's discovery is valuable. Because the impact occurred recently enough that researchers can still observe its fresh features—the bright ejecta, the sharp crater walls, the undisturbed debris field—they can study how impacts shape the Moon's geology in ways that older, weathered craters cannot reveal. That knowledge has practical weight. Both the United States and China have crewed lunar missions in development. Understanding how the Moon's surface responds to impacts, how stable different regions are, and what hazards future astronauts might face all depend on detailed knowledge of crater formation and the processes that follow.
Wagner's discovery came through routine analysis of orbital data, the kind of work that happens quietly in labs and offices, far from the headlines that typically accompany space exploration. Yet it represents the kind of incremental, patient science that builds the foundation for human missions. The Moon is not a static museum. It is still being shaped by the cosmos. McGetchin is proof of that, and a reminder that even in an age of constant surveillance from orbit, the Moon still holds surprises for those patient enough to look.
Notable Quotes
Scientists estimate that an impact of this magnitude happens on the Moon about once in a century or even longer.— NASA
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