GEOFF BENNETT: Scientists say a large piece of a SpaceX rocket today crashed into the moon.

The four-ton upper stage of the rocket is believed to have hit the moon at more than 5,000 miles per hour.

The SpaceX rocket launched a pair of lunar landers last year, but the company's scientists say a combination of solar activity and gravity put it on a collision course with the moon.

For more on why scientists are paying attention amid larger concerns about so-called lunar litter, we turn now to our science correspondent Miles O'Brien.

So, Miles, tell us exactly what crashed into the moon and why.

MILES O'BRIEN: Well, Geoff, you're taking a look at a Falcon 9 rocket on the launchpad.

This is the one that was headed toward the moon.

It launched in January of 2025, two commercial lunar landers on board.

And this is the portion right here.

That is the upper stage, which lights after the rocket gets into orbit and takes the payload on its way to the moon.

If they wanted to, they could have put a little extra bit of fuel on it to nudge it into a solar orbit, but they didn't do that.

And that's why it is headed or has headed and plowed into the moon, or so we presume.

GEOFF BENNETT: So this rocket was on a collision course.

What did scientists predict might happen?

MILES O'BRIEN: They expected it to arrive at the Einstein crater of the moon, western edge of the moon, from our perspective.

And what you're seeing is the location here.

The idea was that it would hit just on our side, the Earth-facing side of the moon, and kick up a plume of dust on the order of 30 miles in height.

Now, scientists really get excited about plumes, Geoff, because they can tell them -- gives them an opportunity to see what the moon is made of, so to speak.

And so what they did was, they projected all of these plume heights and considered the possibilities.

Now, what has happened, we haven't seen actually an image yet.

But scientists tell us, using spectrometry data, that they have found traces of lithium and sodium in this cloud.

But other than that, we haven't seen actual images because it's very difficult to get an image of something this small on the edge of the moon.

Which, after all, is very bright.

GEOFF BENNETT: And that's interesting because, as I understand it, NASA has done this deliberately in the past, and this would explain why.

MILES O'BRIEN: This is 2009.

This is actually one of the cooler missions that NASA has ever done, Geoff.

They flew a spacecraft and deliberately plowed in its upper stage into the moon, kicking up a huge cloud of dust.

And then the instruments on board the spacecraft that was flying along with it captured all kinds of data as it flew through that cloud of dust, and discovered, among other things -- and this is very significant -- water ice.

And this is exactly how NASA has decided to fly its Artemis missions to the south pole of the moon, because they discovered water ice, and that was a big deal.

GEOFF BENNETT: And lots of other big rocket casings have hit the moon, too, right?

MILES O'BRIEN: Yes, that's Apollo 14.

That's its Apollo casing, its casing -- the upper stage, I should say.

And this is what it left behind.

And this is also interesting to scientists as well.

Even if they didn't get a chance to see the plume in real time, as satellites fly overhead like this one did, this is ejecta, which came from deep inside the moon.

They can analyze it and also learn some things.

So it's very interesting.

When you start perturbing things, you're able to determine what things are made of.

Whether they will find any more water here, probably highly unlikely.

But, then again, you never know.

GEOFF BENNETT: Yes, so I hear you say that there is scientific value to all of this, but as more space debris enters low-Earth orbit, it seems like it doesn't really bode that well for the moon as more missions are launched.

MILES O'BRIEN: Well, this is our planet.

I mean, there are thousands and thousands of tracked pieces of space debris.

This is a depiction from NASA which shows just some of the debris that is swarming around our planet.

It's a real problem in low-Earth orbit, which needs to be addressed somehow.

And as NASA, as SpaceX, as humanity starts thinking about flying many more missions to the moon, we should think about this.

The consequences of not handling space debris well are this, and probably this is an opportunity now for the smart people who are designing all these missions to think about space debris around the moon now.

GEOFF BENNETT: Miles O'Brien, we learn so much when we speak with you.

Thanks again for your time.

MILES O'BRIEN: You're welcome, Geoff.