NASA Finds 222-Meter Moon Crater, Largest New Impact Seen in the Solar System

Q: How did a massive building-sized asteroid smash into the Moon completely unnoticed until over a year later?

It went unnoticed because no one directly saw the incoming object, and the Moon is monitored mostly after the fact, not continuously at the resolution needed to catch every impact in real time. The impactor was probably an asteroid or comet fragment only about the size of a three- to six-storey building. That is huge by lunar standards, but still tiny in space and extremely hard to spot before collision, especially if it approached from the Sun’s direction or was simply too faint for Earth- or space-based telescopes. The Moon also has no atmosphere, so there was no fiery streak or sonic event to alert observers as there would be on Earth. NASA’s Lunar Reconnaissance Orbiter did image the area around the time the crater formed in spring 2024, but LRO does not watch the whole Moon continuously at high resolution. It gathers enormous volumes of mapping data that scientists review later. According to reporting on the discovery, the orbiter’s wide-angle images showing the fresh blast pattern were buried in that data stream and were not flagged until 2025, when Robert Wagner noticed an unusually bright patch ringed by a dark halo during a routine review. Only then did researchers compare before-and-after images and confirm the new 222-metre McGetchin crater. So the strike was not invisible; it was unrecognized until someone spotted the surface change in archival orbital data.

3 articles · Updated · ABC News · Sep 17

222 meters across and 43 meters deep, the newly named McGetchin crater is the largest newly formed crater yet identified in the solar system and about three times the previous LRO record.
Robert Wagner spotted the site as a bright spot with a dark halo in Lunar Reconnaissance Orbiter comparison images, then confirmed it with close-up photos and thermal data showing a 6.5-kilometer nighttime “cold spot.”
Researchers say a comet or asteroid roughly the size of a three- to six-storey building struck between April 11 and May 22, 2024, creating an impact NASA says occurs only about once every 132 years.
The blast churned lunar surface material for more than 100 kilometers, suggesting impacts can alter terrain far beyond the crater itself and potentially affect future rover operations.
NASA identifies about 140 new lunar craters a year, and LRO findings indicate the Moon’s top 2 centimeters of soil are being overturned every 80,000 years—faster than previously thought.