Sometime between April and May 2024, something enormous hit the Moon.
It hit hard enough to carve a hole 225 meters wide and 43 meters deep. It ejected rock and dust in all directions — not just a few meters from the rim, but hundreds of meters, with disturbances detected as far as 120 kilometers away. Scientists say an impact that size should happen roughly once every 139 years.
Nobody saw it happen. Nobody heard it. The Moon has no atmosphere, so there was no shockwave, no fireball — just a silent collision in a vacuum, a flash of vaporized rock, and a new scar on the lunar surface that sat undiscovered for months.
The crater was found during a routine review of images from NASA's Lunar Reconnaissance Orbiter Camera (LROC). Planetary scientist Mark Robinson, of Houston-based spaceflight company Intuitive Machines, presented the findings on March 17 at the Lunar and Planetary Sciences Meeting in The Woodlands, Texas.
The timing matters, because NASA's Artemis 2 mission — the first crewed flight around the Moon since 1972 — is scheduled to launch no sooner than April 1, 2026. Eight days from now.
Act 1: What Was Found
The Lunar Reconnaissance Orbiter has been photographing the Moon's surface since 2009. Its primary mission has been mapping — creating the most detailed catalog of lunar terrain ever assembled. A secondary benefit of continuous monitoring is the ability to detect change: new features that appear between images taken months or years apart.
The 2024 crater was identified by comparing before-and-after images. The crater sits on a geological boundary — the edge between the cratered, craggy lunar highlands and a wide, flat mare, which formed from ancient lava pooling on the lunar surface billions of years ago. That location is geologically interesting because it spans two distinct material types, which affects how an impact propagates.
The crater's depth and steep edges indicate it formed in particularly strong material — consistent with the solidified lava of the mare boundary. The slightly elongated shape suggests the impacting body didn't hit straight-on but at an angle, and that the subsurface geology is not uniform beneath the crater floor.
Robinson noted the progression of LROC discoveries: the first new crater spotted after the orbiter's 2009 launch was 70 meters wide. Robinson joked at the time that the bar had been set and the next one would have to be 100 meters. "Now, lo and behold, we have 225 meters," he said at the conference.
Act 2: How Rare Is "Once-in-a-Century"?
The estimate that a 225-meter crater forms only once every 139 years is derived from two bodies of data: the Moon's accumulated cratering history and models of the near-Earth object (NEO) population — the asteroids and comets whose orbits bring them close enough to potentially hit Earth or the Moon.
The Moon's surface is the solar system's best natural geological record. Unlike Earth, where erosion, tectonic activity, and weather constantly resurface the landscape, the Moon preserves billions of years of impact history in near-perfect condition. By counting craters across different size ranges and dating crater ages, scientists can build statistical models of how often impacts of different sizes occur.
Those models suggest the Moon is hit by objects capable of forming 100-meter-plus craters roughly every few decades. Objects capable of forming a 225-meter crater are rarer — the 139-year estimate reflects the probability based on the known NEO population and historical cratering rates.
It's worth being precise about what "once every 139 years" means. It doesn't mean the last one was exactly 139 years ago, or that the next one is 139 years away. It means: if you observe the Moon continuously for 139 years, you'd expect to see one event of this magnitude on average. You might see two in a decade, then none for 200 years. Probability doesn't operate on a schedule.
The fact that a 225-meter crater formed in 2024 — while we happened to have continuous orbital surveillance — is either a lucky coincidence or a reminder that rare events are always happening somewhere. We just don't usually have the instruments to catch them.
Act 3: The Artemis Problem
The crater discovery is scientifically significant on its own terms. But its timing — announced nine days before Artemis 2's scheduled launch — has made it a talking point about lunar mission safety.
Artemis 2 will not land on the Moon. It will carry four astronauts on a 10-day circumlunar trajectory — a loop around the Moon and back to Earth — similar to the Apollo 8 mission in 1968. The crew will not set foot on the surface. They will pass within roughly 9,000 kilometers of the Moon at closest approach.
At that distance, the crater discovery poses no direct risk to Artemis 2. A meteor impact on the Moon doesn't generate any meaningful ejecta hazard at 9,000 kilometers, and Artemis 2 isn't arriving during or immediately after an impact. The crater formed in 2024.
The more significant implications are for the future missions:
Artemis 3, currently scheduled no earlier than 2027, will attempt the first crewed lunar landing in 54 years, targeting the lunar south pole — a region of intense scientific and geopolitical interest because of confirmed water ice deposits in permanently shadowed craters. Beyond Artemis 3, NASA and its international partners (ESA, JAXA, CSA) have outlined plans for a permanent outpost, the Lunar Gateway station in orbit, and eventually a sustained human presence on the surface.
It's the sustained surface presence where the crater discovery becomes operationally relevant.
Act 4: Building on a Shooting Range
The Moon is not a benign environment. This is well understood — radiation, extreme thermal cycling (day temperatures of +127°C, night temperatures of -173°C), and the complete vacuum require specialized engineering for any surface structure. But the impact hazard has historically been treated as a low-frequency background risk rather than a primary design driver.
The 2024 crater complicates that framing.
Robinson's presentation at the Lunar and Planetary Sciences Meeting specifically highlighted the engineering implications of the ejecta field. The crater's blanket of ejected rock and dust extends hundreds of meters from the rim. More critically: instruments detected disturbances — smaller secondary impacts from ejected material traveling as projectiles — as far as 120 kilometers from the crater's center.
That ejecta travels at approximately one kilometer per second. At that velocity, a particle the size of a grape can punch through standard structural materials. Engineers designing orbital hardware typically model micrometeorite impacts — particles measured in millimeters moving at tens of kilometers per second. A larger chunk of lunar rock moving at one kilometer per second occupies a different threat category.
Robinson's language was direct: "You've got to protect your assets to withstand small particles hitting you at order of magnitude a kilometer per second." For a lunar habitat, that means shielding considerations well beyond what current ISS-class construction assumes. For lunar surface vehicles, it means the possibility that a once-in-a-century impact 100 kilometers away damages or destroys equipment with no advance warning and no ability to seek shelter.
The Moon has no emergency broadcast system. There is no alarm that fires when an impact occurs 50 kilometers away and ejecta is inbound. Future astronauts working on the lunar surface will be operating in a hazard envelope that includes this threat — and current mission architectures haven't fully grappled with how to mitigate it.
Act 5: What This Changes, Practically
The immediate effect of Robinson's announcement is on engineering standards conversations, not operational decisions. Artemis 2 is not affected. Artemis 3's landing site selection — targeting the south pole — is driven by water ice access, not proximity to the 2024 crater, which is in a different region of the Moon.
The longer-term effects will likely show up in three areas:
Habitat shielding standards. NASA's current Artemis Base Camp design concepts use regolith (lunar soil) shielding — essentially berming the habitat under several meters of lunar dirt — as the primary radiation and micrometeorite protection strategy. Ejecta from large impacts represents a different threat vector that multi-meter regolith berms may not adequately address at the roof. Expect updated modeling requirements in future design specifications.
Early warning systems. There is currently no network capable of detecting a large incoming object and issuing an impact warning with enough lead time for lunar surface operations to take protective action. The 2024 crater went undetected until orbital photography spotted it months later. For a permanent crewed outpost, developing some form of seismic or optical early warning capability — possibly from the planned Lunar Gateway orbital station — will likely become a mission requirement.
Site selection for permanent infrastructure. The risk of large impacts and their ejecta fields may push planners toward siting critical infrastructure in permanently shadowed craters or lava tubes — natural geological shelters that would offer protection not just from radiation but from high-velocity projectiles. Lava tube exploration has been a scientific priority for years; the 2024 crater discovery gives it an additional engineering rationale.
The Bottom Line
A 225-meter crater formed on the Moon in the spring of 2024. It wasn't noticed for months. When the data was finally presented to the scientific community on March 17, 2026, the headline number — once every 139 years — was remarkable enough to make international news, but the deeper implications got less coverage.
The Moon is a hostile environment in ways that are still being quantified. The crater isn't a reason to stop the Artemis program — the science and strategic rationale for a human return are well-established, and the probability of any given lunar structure being directly hit by a 225-meter-class impact in a given year is extremely low. But it is a data point that updates the risk models for sustained surface operations.
As NASA pushes toward not just visiting the Moon but living there — building habitats, storing equipment, conducting multi-month surface missions — the engineering margins have to account for a threat that the Apollo program, which never planned to stay longer than a few days at a time, never had to solve.
Artemis 2 launches in eight days. The four astronauts aboard will loop around a Moon that, as of last spring, is carrying a scar the size of two football fields that wasn't there the year before. They won't land. But the people who come after them will.
And those people will need shelter that doesn't yet exist, from a threat that was just quantified last week.