A rock the size of a small building hit the Moon and nobody noticed for a year and a half

I love that this is still possible in 2026. We have a spacecraft circling the Moon taking pictures all the time, something big hit the surface anyway, and it took about eighteen months before a person spotted it.

NASA announced this week that the Lunar Reconnaissance Orbiter found a brand new crater. It's called McGetchin, after the lunar scientist Tom McGetchin. It's about 222 meters wide and 43 meters deep, and it formed sometime between April 11 and May 22, 2024. That makes it the largest freshly formed crater anyone has identified anywhere in the solar system. The thing that made it was an asteroid or comet about the size of a three to six story building.

The way it turned up is the part I keep thinking about. Robert Wagner, who works with the camera data from the orbiter, was going through a global map on October 24, 2025. He was stacking hundreds of before and after images with software that highlights changes. He said the debris pattern was by far the most obvious one he had ever seen. So the evidence was sitting there in the data the whole time. Someone just had to run the right comparison.

There's a nice extra detail from the orbiter's thermal instrument. Around the crater there's a "cold spot" about 6 kilometers across that is roughly 9 degrees Celsius cooler at night than everything around it. The impact fluffed up the soil, so it holds less heat.

NASA says an impact this size happens on the Moon about once a century. We happened to have a camera pointed at it, and then it took us a year and a half to look.

Source: https://science.nasa.gov/solar-system/moon/nasas-moon-orbiter-spots-new-once-in-century-moon-crater/