Since launching in 2009, NASA's Lunar Reconnaissance Orbiter (LRO) — a robotic satellite about the size of a minivan — has taken more than 3 million photos of the lunar surface. This week, scientists studying a few hundred of those photos announced what they're calling a "once-in-a-century" discovery: the biggest, freshest impact crater ever seen in the solar system. ‪It's the result of a building-size meteorite that slammed into the moon just two years ago.

The new lunar pockmark, named McGetchin crater after the late geologist and lunar scientist Tom McGetchin, is about 728 feet (222 meters) wide, on average, and 141 feet (43 m) deep ‪—‬ imagine a hole as long as two American football fields and deep enough to fit a 14-story building inside.

"We know generally that there's more small things in space than there are large things, so that means we tend to get a lot of small craters on the moon and very few large craters," Julie Stopar, a senior scientist at the Lunar and Planetary Institute and deputy principal investigator on the LRO's camera team, told Live Science. "So something the size of this crater, we only expect to encounter that once every 130 years, approximately."

McGetchin is nowhere near the moon's largest crater; that honor goes to the South Pole-Aitken basin, a gargantuan gouge about 10,000 times wider than the newly discovered crater. But McGetchin is the largest new crater. Appearing seemingly out of nowhere in images from spring 2024, it's the biggest one scientists have seen in the 17 years that LRO has been active. And now that it's known to the world, some intrepid skywatchers think they've spotted the crater's bright, white debris ring from Earth.

The team described their findings in two papers published Sept. 16 in the journal Science Advances. Live Science spoke with Stopar to find out what this fresh crater can teach us about lunar geology, impact rates and potential risks to the future human visitors to the moon.

Dr. Julie Stopar is a staff scientist at the Lunar and Planetary Institute where she leads research on lunar geology and surface evolution. She is the deputy princial investigation for NASA's Lunar Reconnaissance Orbiter camera, which discovered McGetchin crater.

Brandon Specktor: The moon is riddled with craters. What's so interesting about this new one?

Julie Stopar: On one hand, it's a nice crater because it's so fresh and new. It hasn't been weathered. On Earth, we see the remnants of impact craters, but a lot of the original details are lost through weathering and degradation and time. But the moon preserves all of that much better.

This crater, in particular, is so fresh and young — it's only about 2.5 years old. It's in really, really good condition. We can study it to understand how impact cratering occurs and all the processes that go along with it.

The other cool thing is that it impacted on the boundary between two different types of deposits on the moon. There's the volcanic mare deposits [dark patches visible from Earth] and there's the highlands, which are ancient crustal material. The highlands are brighter and tend to be hillier, more mountainous, whereas the mare are flat plains, and they're very dark. This impact seems to have occurred right on the boundary between those two areas, so that's reflected in the materials that are excavated by that crater.

BS: The meteorite that made this crater was the size of a three-to-six-story building, according to your team's estimates. Could we have seen this impact from Earth?

JS: Yes. This is a relatively large impact, and from Earth, we have observed flashes associated with smaller impacts. So I think it's possible, under good conditions, that this may have made a flash. We don't know if anyone was watching, though — so if somebody out there has videos that they can dig through, they could go back and look for it.

BS: This impact happened in April or May 2024. One of your colleagues discovered the crater in LRO data in October 2025. Why did it take so long?

JS: LRO orbits the moon about 12 times each day. While we're going around, we can only image a really small portion of the moon on each pass. So you can imagine it takes many, many orbits to go around the moon and to reimage each part of the surface. When we don't have an impact flash to help us decide where to look for these craters, it's basically a random search.

Over time, we eventually will get repeat imaging [of the same area], but it takes years to get that. On top of that, the processing that it takes to make the before and after images

takes a lot of work; basically, you're looking through all the images that have been taken of the moon under the right conditions, and it just takes a lot of time and effort to process that.

BS: Your colleague, Robert Wagner, says he "stopped and dropped everything" when he discovered the crater in LRO's data. What was your reaction when he first showed it to you?

JS: I was surprised that it was so large! But I've seen a lot of similar craters on the moon, so my actual first thought was, "Oh my gosh; this crater might actually help me constrain how old all of these other craters are!"

BS: So because you know this crater is so fresh, it's helping you date other craters you've seen too?

JS: Yes, I've been looking at a bunch of craters, which I think look morphologically [their shape] and albedo-wise [how much light they reflect into space] very fresh. They have the bright ejecta [the material that gets blasted out from the meteor impact]; they have crisp rims. But I don't know how old they are, because they were there before the LRO. I think they're young, but I don't have any proof of age. So that was my first thought: "Oh my gosh; this makes me feel so much better if all these other craters I'm studying are still in really good condition like this one is."

BS: What, specifically, do you hope to learn about the moon from this crater?

JS: There's hope that we can use this to help understand the current impact cratering rate. How much and how often do different sizes of debris in the solar system impact the moon?

And that's important, because people want to go to the surface for exploration, send landers, start building moon bases and so forth, and there's some concern that impactors will be a hazard. So it would be helpful to have a better idea of whether that's a really frequent concern or only a once-in-a-while concern. We can also study things like how the impact angle, the target materials, and the velocity and type of impactor play a role in forming craters.

This crater will help us better interpret all of the others as well. I think this would be a really good crater to go get samples from, because we know when it formed and we have a lot of questions we can answer with that.

BS: How do you see human-made impacts fitting into this? In recent years, several spacecraft have crashed into the moon. Do you see any risks there or more opportunities to study craters?

JS: At this point, it's not too much of a concern to myself about human-made objects destroying natural habitats on the moon. Other spacecraft impacts, like the boosters from the Apollo program, made craters a long time ago. But I think, as there are more people and countries and even companies going to the moon, they'll have to get coordinated so as to not interfere with each other's activities — because that would be a problem. It's just a reminder like, "Hey, guys; you need to talk to each other and get coordinated and make sure you're keeping track of these impacts and your debris, and you're working together."

Otherwise, those craters are interesting because we know the impactor's mass and shape beforehand. It gives us a new insight into how craters form when you have irregularly shaped masses, like hollow cylinders and things like that. They'll also tell us about the moon's surface as well, because it's a different type of impact and it's got a different kind of energy to it and a different shape. So we do learn a lot about the cratering process in general from those.

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