A rock the size of a six-story building gouged the Moon’s biggest crater in a century

Robert Wagner was running a routine data-quality check on a global mosaic of the Moon on Oct. 24, 2025, when an unusually bright spot circled by a dark halo stopped him mid-scroll. Comparing older and newer images of the same stretch of terrain, the image-processing specialist realized he had found something that had not existed months earlier: a fresh scar on the Moon’s eastern edge, 728 feet wide and 141 feet deep, torn open by an object roughly the size of a three- to six-story building. Scientists now call it the largest newly formed crater ever documented anywhere in the solar system.

The impact struck sometime between April 11 and May 22, 2024, though nobody on Earth noticed until Wagner’s review more than a year later. Researchers reported the find Sept. 16 in Science Advances and named the crater McGetchin, after pioneering lunar scientist Tom McGetchin. Impacts capable of carving a hole this size, the team estimates, strike the Moon only about once a century or longer.

An image specialist’s routine scan

Wagner processes imagery for the Lunar Reconnaissance Orbiter Camera, a three-camera system that has circled the Moon for more than 17 years. Part of his work involves stacking hundreds of Wide-Angle Camera frames taken years apart and running them through software built to flag change: pixels that stayed the same turn gray, and anything different shows up as a bright or dark patch. The software is a blunt instrument. It flags every small shift in lighting or shadow along with genuine craters, producing hundreds of false alarms for every real one, so Wagner has learned to look past most of the noise and check only the patterns that look like actual debris.

Wagner said he stopped what he was doing and started looking into the spot the moment the bright patch caught his eye. Real craters typically show up as pixel-wide points with a faint, fuzzy halo of ejected regolith, subtle enough that confirming one usually takes close inspection. McGetchin’s halo needed no squinting. Wagner called it by far the most obvious impact debris pattern he had ever seen in one of the orbiter’s images.

Three stacked school buses of fresh depth

Once Wagner flagged the site, mission scientists turned to the orbiter’s Narrow-Angle Camera, which resolves detail down to about 3 feet per pixel, far sharper than the wide-field images that first caught his eye. Those close-ups confirmed the crater’s size and shape: 728 feet across, about the length of two football fields, and 141 feet deep, enough to swallow three yellow school buses stacked one on top of another.

That scale points to an unusually large impactor. Researchers put its likely diameter at somewhere between three and six stories, far bigger than the roughly 43-inch rocks, about the size of a monster-truck tire, that typically produce the smallest craters LRO can distinguish. A follow-up paper is expected to narrow down the object’s exact size and the force behind the collision.

A four-mile-wide cold ring left behind

After the visual discovery, scientists pointed LRO’s thermal instrument, Diviner, at the same coordinates and found something the cameras alone had missed: a roughly 4-mile-wide patch of ground around the crater that runs about 16 degrees Fahrenheit cooler than its surroundings at night. Researchers described the cold spot in a second paper published the same day in Science Advances, alongside the discovery report.

The cooling happens, the team concluded, because the impact fluffed up the regolith ringing the crater, leaving it less densely packed and therefore worse at holding heat after sunset. The cold ring’s reach, far wider than the crater itself, shows that a single impact can reshape surface conditions well beyond the hole it leaves, a detail that could matter for how future rover wheels grip the ground nearby.

Diviner’s post-impact readings were collected between Nov. 15, 2025, and Feb. 18, 2026, months after Wagner’s initial spot, and compared against a pre-impact baseline the mission had already built from years of nighttime temperature passes. Matching the two data sets let researchers isolate exactly which patch of ground had changed temperature and rule out ordinary seasonal variation as the cause.

A mission that has already logged a thousand scars

LRO has spent more than 17 years mapping the Moon’s topography, composition, temperature and radiation environment, and its team has identified at least 1,000 new impact craters and 100,000 other surface changes over that span. Most are tiny by comparison. Scientists estimate that objects large enough to leave a 30-foot crater, the length of a three-story building laid on its side, strike the Moon roughly 140 times a year, but the vast majority go undetected in orbital images.

McGetchin stands apart from that steady background rate. An object able to gouge a crater 728 feet wide and 141 feet deep, and to chill four miles of surrounding ground overnight, is the kind of collision LRO’s own scientists say happens only once a century or longer, and Wagner’s flagged image is, so far, the only record of it.

NASA frames the find as more than a curiosity. The agency is pushing to expand human presence on the Moon through the Artemis program, and a catalog of fresh impacts, however rare the largest ones are, feeds directly into how mission planners think about surface hazards for future crews and hardware. A crater this size sits far from any planned landing zone, but the cold ring around it is a reminder that a single strike can alter surface conditions across an area many times larger than the hole itself.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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