In the space digest for September 21, an item flashed by that I initially scrolled past as routine: LRO found the largest fresh crater on the Moon, and around it — "a cold halo that Diviner can't explain." Fresh craters usually look brighter than the background, and their rocky ejecta hold onto nighttime heat longer. But this was the opposite: minus nine degrees during lunar night. An inverted expectation — the tastiest thing that happens in science.
I wanted to understand: is this really a mystery, or did the compressed retelling make it one. Spoiler: partially — yes, it did. The real sensation turned out to be somewhere else, and it's bigger than any single crater.
On October 24, 2025, Robert Wagner, an image processing specialist at Intuitive Machines working with LROC cameras, was doing what his team does every few years: stacking hundreds of images from the "global" wide-angle camera (WAC) across different years and running them through software that highlights changes. Everything that didn't change became gray; everything that changed became a light or dark spot. Hundreds of false positives: shadows, lighting, noise. Wagner manually filters out the garbage, hunting for "fluffy halos" around bright points — splashes of regolith around new craters.
This spot was different. "The most obvious impact ejecta pattern I've seen in such images," he recalled later. The spot stretched for hundreds of pixels, and a WAC pixel is the size of a football field.
Cross-checking the archives showed: in spring 2011 this spot was still clean, but by summer 2025 a bright point with a dark halo was already sitting on the eastern limb of the Moon, at 51.35° north latitude and 67.18° east longitude. The next six months the team ran the narrow-angle camera (NAC, one meter per pixel) at every opportunity — the imaging window for this zone opens only a few days per month. Result: a crater 222 meters in diameter and 43 meters deep, the impact occurred between April 11 and May 22, 2024. According to impact frequency models (Neukum production function), an event of this size happens on the Moon roughly once every 132–139 years. In all 17 years of the LRO mission, the largest "fresh" crater was 70 meters — the new one is three times bigger. This is the largest crater whose birth humanity has ever witnessed anywhere in the Solar System.
Now about the "mystery" that made me dig into this topic in the first place. The Diviner radiometer, a thermal imager aboard LRO, imaged the area during lunar night (November 15, 2025 — February 18, 2026) and saw around the crater a cold spot about 7 kilometers wide: the ground there is 8–9 kelvins colder than the surroundings. To the eye this looks like an anomaly — a fresh impact should churn up and "insulate."
But physics found an explanation, and it's elegant: the impact didn't add heat — it added insulation. The upper layer of regolith around the crater became less dense ("fluffed up," as the authors write): more vacuum pores appeared between particles, and in vacuum, heat on the Moon is transferred mainly through particle contacts. Less dense soil conducts heat worse — and at night this hits the surface: it's cut off from the warm depths, it has nothing to "warm up" from below, and it freezes out noticeably more than its dense neighbor, whose soil slowly releases the reserve accumulated during the day. No mysticism: pure thermophysics of loose vacuum soil.
So why did the digests write "nobody knows"? Because the mystery wasn't "why cold," but "why so far." And that's actually interesting.
The second paper in Science Advances (the Diviner team, Powell and Greenhagen with co-authors) checked all fresh craters larger than 20 meters found to date, and discovered: cold spots are produced by all craters larger than ~30 meters. This isn't a unique feature of just this crater, but a standard consequence of any fresh impact. The anomaly grows with crater size — meaning large impacts decompactify regolith deeper. Extrapolation across all craters over millions of years leads the authors to a conclusion worth reading twice: cold spots in total rework the upper regolith at a rate comparable to classic "impact gardening" — that is, they themselves are an underestimated driver of the evolution of the entire lunar surface.
The geometry is impressive in numbers from the first paper. Surface disturbances are traced more than 100 kilometers from the impact point — over a thousand crater radii. The previous model assumed that high-velocity "jetting" — the outflow of material at first contact with the impactor — goes at angles around 2° to the surface; observations showed more than 10°. Ejecta went in at least two waves. The rim rose 8 meters — Pike's 1977 formula predicted 9, a one-meter miss for an expression without a single correction for this specific case. Walls slope at 25–40°, on the floor — a pit and a bench with slopes exceeding 35°, and the darkest spots on the walls — impact-melted glass.
The largest ejected block — 13×9×6 meters. Its height was determined by shadow in a ShadowCam image — a camera that "photographs" not with sunlight, but with earthshine: solar rays reflected from our planet back to the Moon. Measuring a boulder the size of a railcar by the reflection of your own planet — now that's what I call engineering.
And a bonus for cartographers: the crater landed right on the boundary between mare basalts and ancient anorthositic crust. The ejecta lifted material from a depth of more than 20 meters, where the "smeared" mixing of rocks by billions of impacts hasn't yet been eroded — and rock from two geological epochs laid around the pit with different albedo, like an exposed cross-section.
The phenomenon itself isn't news: the first systematic works on lunar cold spots came out in 2014 (Bandfield, Hayne and colleagues in Icarus), and Williams's 2018 catalog counts more than 2000 cold spots around craters from 43 meters to 2.3 kilometers. A spot's lifetime — from hundreds of thousands to a million years: then subsequent micrometeoroids gradually "tamp down" the soil again, and the thermal signature fades.
From this catalog, by the way, they also extracted unexpected cosmography: cold spots are distributed unevenly across the Moon — there are more on the "leading" side, facing forward along the orbital motion. The asymmetry encodes the average impactor velocity: it came out to about 8.4 km/s, surprisingly low. The thermal map of craters turned out to also be statistics on the population of near-Earth asteroids.
The subtitle promises a man named after a crater, but it's exactly the opposite — and that's the whole point: the crater was named after a scientist who died 45 years before a guest from the sky left a pit in his field. Thomas McGetchin (1936–1979) — an almost cinematic figure. Declined a professional baseball career, became a geologist; wrote his dissertation at Caltech under Lee Silver and Eugene Shoemaker — that same Shoemaker whose name would later be given to the comet that collided with Jupiter. Worked on the Apollo field geology team, trained astronauts, studied the ballistics of volcanic ejecta — and recorded the sound of eruptions to analyze it with an acoustic engineer. He died at 43, having managed to become one of the founders of crater formation mechanics — a science that now, in 2026, measures the crater bearing his name with exactly the same tools.
A separate irony: the LROC team in the same press material reminds us that not all new craters on the Moon are natural. Spent rocket stages and retired spacecraft leave their own "ejecta pattern" on the regolith. Impact gardening is now done by us too.
The pragmatic layer is the freshest: NASA directly links the discovery to the program for sustainable presence on the Moon. If an impact on the scale of McGetchin (which happens only once in 132 years) can shake up the surface within a radius of tens of kilometers, then lunar infrastructure — landing pads, habitat modules, solar panels — must be designed taking into account not only local events, but also long-range consequences of distant impacts: flows of small particles flying at velocities of kilometers per second from tens of kilometers from the epicenter. Tactics also change: cold spots are a ready marker of surface "freshness," by which you can date the geological age of any site without a single soil sample. And for rover wheels, by the way, loosened regolith with altered bearing capacity — that's not an abstraction, but a difference in traction.
The researchers formulate the final chord dryly, but the scale is grim: cold spots, it turns out, restructure the Moon's surface layer almost as intensively as the craters themselves. That is, the Moon isn't a frozen museum, but a surface continuously repainted by impacts, even those that didn't leave a visible pit. It's just that its paint is thermal, and you can only see it at night.