That's no moon...

21m
It's a quasi-moon. Or, a quasi-satellite. Whatever you want to call it, it's hanging out near Earth. And it could be the source of some fascinating new science.

Guests: Nick Moskovitz, astronomer at Lowell Observatory

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Runtime: 21m

Transcript

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Last August, astronomers detected a small object in space.

This thing that has been hanging out near us, apparently, for decades, doing vaguely moon-like sorts of things.

People got excited about it,

but

there was this kind of terminological kerfuffle around what to call it. In articles, on TikToks, on news shows, people were pretty quick to say that it was not a second moon.

But then they would throw out different terms. So people would talk about quasi-moons and quasi-satellites, sometimes also explaining related terms like mini-moons.

And it all gets a little confusing. So for now, let's just call this object by its name.

2025PN7. So it's not the most exciting name.

I hope somebody comes up with a proper name or a nickname for it at some point. But for now, we just kind of refer to it as PN7.

This guy's name is Nick Moskowitz, which in my opinion is much better than 2025 PN7.

And I reached out to him because he spends time at Lowell Observatory in Flagstaff, Arizona, researching space objects in general.

When I asked him if PN7 was a moon or what, he hesitated for a moment. He did tell me PN7 is one of many objects in the general vicinity of Earth.

These are what we refer to generally as near-Earth objects, and they're cleverly named that way because they get close to the Earth.

There are almost 40,000 known near-Earth objects in the solar system that we track and keep track of.

But PN7 is maybe a little more special than some near-Earth objects, because there are lots of objects that just kind of whiz past us, right? Or only cross our paths sometimes.

And then there are the objects that stick around for a while.

Those can be many moons, which orbit the Earth, or they can also do what PN7 seems to be doing, which is to say, orbiting the sun, but doing it in such a way that keeps it close to the Earth for a while.

And so I think probably a term that most people in the community would agree on is a quasi-satellite.

So that's what I'm going to refer to PN7 as, a quasi-satellite. But if you're still confused, that's fair.
As I told Nick, I kind of was too. Have you ever seen the QVC clip?

And look at this one. This is what we call emerald, but really it's more like a sea foam.
I love that color.

Where it's like two QVC hosts. It almost kind of looks like what the Earth looks like when you're a bazillion miles away from the planet moon.
Yes. And they're going.

The moon is also a star.

Isn't the moon a star?

No, the moon is a planet, darling. The sun is a star.

And then someone's like, no, the moon is a planet.

Didn't you do that thing in grade school where you had to name the planets and there was Uranus and there was Saturn and the one with the rings and that and then the Earth and with the moon is never in there dude.

It's not a planet.

All right, here look, this is Keyline.

There's something about this that like sort of reminds me of that. 100%.
This is this is I haven't seen that clip. I don't know.
It sounds awesome.

But when it comes down to it, it doesn't really matter what label you apply to these objects. They're still just interesting things to study.

Like they're doing interesting things that are rare and cool. And we geek out on that and get excited about it and study these things to learn something that we didn't know beforehand.

So that makes it exciting to me.

So, this is Unexplainable. I'm Bird Pinkerton.
And you can call objects like this whatever you want. PN7, quasi-moon, quasi-satellite.
Just don't call them uninteresting.

Because Nick Moskowitz is going to tell us some of the things we can learn from them.

Also, just in case you were wondering, the QBC house did eventually sort of figure out what the moon is.

The moon is what?

A natural satellite.

But things live on it. That means it's a planet.

Is that what Google said? I don't know what that is. No, I don't like that at all.
I don't even know what that means.

I do. I use Google all the time.

So, you have detected an object in space, something that seems to be acting like a mini-moon or a quasi-satellite. Congratulations.

Now, what can you learn from it? Nick says, kind of the first step is to figure out whether or not it is space trash. It turns out that when humans put stuff into space, we leave junk behind.

We leave rocket bodies and boosters and defunct satellites and things like that. We're not good at cleaning up after ourselves here on Earth and definitely not in space.

And pieces of space junk hang around the Earth-Moon system in a very similar way. They're doing laps around the Earth just like some of these natural objects do.
We're making mini-moons.

We're making, yeah, we've made a whole population of thousands of mini-moons that are artificial in nature, man-made things.

But.

Let's say you've poked around, done your homework, and you've determined that this is not just space garbage, which is interesting, but a different kind of interesting from a space object like PN7.

If your object is not space trash, you now get to figure out if it is, essentially, a little piece of our actual moon.

Like moon debris. We know by looking at the moon,

our primary moon, our permanent moon, that it has lots of craters on it. And some of those craters are quite large, you know, tens, if not hundreds of miles across.

When you form a big crater like that, you kick off a lot of ejecta. You think of sort of a, you know, a rock smashing into a pond.
You're going to splash a lot of water out of the pond.

On the analogy for the moon, when a crater gets formed from an impact on the moon, the ejecta from that gets splashed out into space.

Studying moon debris like this could potentially teach us about the history of the Earth and of our moon.

Nick hopes we might someday be able to trace specific bits of moon debris back to the craters where they came from, and he says that would in turn help us check the computer models we have of what happened to the moon in the distant past.

But if our space object is not moon debris or space junk, then it could also be a third thing. An asteroid.
It's a chunk of rock that formed around the sun four and a half billion years ago.

It's been floating around the solar system.

And by studying these, we're really able to study sort of a time capsule of what's been happening in the solar system for four and a half billion years, which is pretty cool.

That's what most people think PN7 is. An asteroid that has journeyed over to us and is hanging out for a while.

And this kind of space object is scientifically fascinating for a bunch of reasons, which we will get into after some very fascinating ads.

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Welcome back. As Nick was telling me, it seems like PN7 is an asteroid that has traveled in from elsewhere in the solar system and is now hanging out near us for a while.

And asteroids like this can potentially help us learn about our solar system and its history. Because when it comes to learning about that history, here on Earth, we have this problem.

Imagine that someone gives you some little colorful clay pots for your birthday, okay?

You take the clay out, you roll it all together for some reason, so the colors are all mixed up.

And then you fold the clay and you tear it apart and you re-roll the different parts and you bake them maybe.

And then for some reason you decide to grind them all into dust and then you mix everything with water and you roll it out again.

It's very difficult, right, to go from that final product back to your original little pots of clay.

And that

is basically what earth rocks are like.

Here on Earth, we have weathering and tectonic plates and all kinds of forces that fold and melt and blend our rocks into something very different from the original rock that they came from.

So it's not always easy to figure out what our rocks were like when the planet first came together.

If you go to asteroids though.

Asteroids and things that don't have atmospheres don't weather. There's no wind on asteroids.
There's no rain. There's no plate tectonics.

There's none of the things that produce all the rocks that we see here on the surface of the Earth that look so familiar to us.

On asteroids, there is radiation from space, but the rocks should be at least closer to the original pots of modeling clay.

And that means that they are potentially amazing sources for the history of the solar system.

Of course, asteroids also have a problem. They are very far away, which makes them hard to study.
But every once in a while, the universe kind of throws us a bone in the form of a meteorite.

These are chunks of material that start on the surface of an asteroid, make their way to the Earth in some way that we don't really understand,

appear in the night sky or the daytime sky as a shooting star or a bright flash of light as that rock is passing through our atmosphere.

And if that rock is big enough to survive that intense heating of being a shooting star, it can land on the ground and be picked up as a meteorite.

These are some of the most valuable scientific time capsules that we can go out and put our hands on. Not even just time capsules, like space capsules, also.
They're space rocks, right?

They're amazing.

So meteorites are incredibly valuable, an incredibly valuable tool because we can go and pick them up, study them in a laboratory in detailed ways that we would never be able to do with a rock that's out there in space that we're just studying remotely with a telescope.

We think of that sort of process of meteorite delivery to the surface surface of the Earth as nature's version of a sample return mission.

So we can send spacecraft out to go pick stuff up off the surface of an asteroid or a comet, hopefully one day, and bring that back to Earth.

But that costs like a billion dollars. A meteorite is like a free sample delivery, courtesy of the universe.
And it means that Nick can go out and hold something from space if he wants to.

You're holding these rocks, you're looking at it, and this thing is older than the Earth.

Right? It's literally the oldest thing you can put your hands on. And it's like, that's just amazing, right?

We've studied meteorites to learn about the history of the solar system and to try and understand how we got water on Earth.

But they also have a problem, which is we don't have a ton of context for them.

So there is a fair amount you can learn from studying a rock's makeup, but ideally, you want as much information as you can get about where it's been.

With asteroids, we have a fair amount of information because we can use math to try and study their trajectory.

We lose that context from the vast majority of meteorites, meaning we don't know where they came from in the solar system.

So, we have asteroids in space, which have lots of context, but we can't hold them in our hands and analyze them in detail.

And we have meteorites, which we can analyze in detail, but which often have less context.

It kind of feels like an O'Henry story.

Except, this is where quasi-satellites might come in. They're still in space, so we can get some context on them, but they're also closer to us.
So, Nick says they're somewhat easier to examine.

We can study these objects in detail as, you know, sort of case studies and say, okay, this is the kinds of things that are coming into the Earth-Moon system.

Let's understand what it looks like through a telescope and then compare that to the objects that are not just passing by or, you know, doing a few laps and then leaving, but instead compare it to the ones that actually hit the Earth and are recovered as meteorites.

And if we can improve and establish meaningful linkages between what we see remotely with our telescopes in terms of asteroid properties and in the laboratory with meteorites, then we can gain a much more holistic view of the solar system.

There are also other reasons that it could be cool to gather more in-depth data about asteroids.

There's a lot of talk right now about what's called situ resource utilization, ISRU, which really means just using the stuff in space to produce material that'll be valuable for spacecraft or human exploration.

So the thinking is basically,

what if asteroids could be like refueling stations as we go through space or just useful sources of material?

It's a pretty far in the future kind of idea, but these little asteroidal quasi-satellites could help us understand more about how realistic it might be.

So that's the sort of exploration and resource utilization perspective on these objects.

Maybe the most exciting next step would be if we could go examine something like a quasi-satellite directly. We haven't known about them for all that long, actually.

We found the first one back in the 2000s, and no one has gone out to take a sample of a mini-moon or a quasi-satellite directly yet.

But there are a bunch of different organizations that have gone out to kind of take a look at a whole bunch of different near-Earth objects.

NASA had a recent mission called OSIRIS-REx that went to a near-Earth object called Bennu. That object in particular was targeted because we think it's, we now know that it's water and organic rich.

OSIRIS-REx touched down on the surface of Bennu, picked up some samples and brought them home. So we now have pieces of Bennu curated and brought back to Earth.
That's one example. There are others.

The Japanese have launched a pair of just amazing missions called Hayabusa and Hayabusa 2, both sample return missions, going to near-Earth objects and interacting with the surface and in both cases bringing stuff home for us to study in the laboratory.

The Chinese are getting involved in this as well and have a whole fleet of planned missions coming up. And actually, one of those is going to be targeting one of these quasi-satellite kinds of things.

So we'll be able to get

that particular target, we think, is one of the lunar ejecta

things.

But we'll find out, hopefully, when the spacecraft gets there, you get up close imagery, get more detailed information.

You can say, hopefully, with better certainty of whether or not this thing actually is a chunk of the moon. Does it look like the moon or does it look like something else?

So yeah, it's an exciting time to be sort of involved in this area of planetary exploration. It's a really rapidly evolving space.

So, watch this space.

And meanwhile,

we'll probably continue to find cool objects floating around near us.

And instead of talking about whether we should call them second moons or quasi-satellites or whatever else, I would argue we should talk about how cool it is that we have essentially tiny time capsules for neighbors.

Just like little archives of our solar system

that are out there to be explored.

This episode was produced by me, Bird Pinkerton. It was edited by Joanna Solotarov, who also runs the show.
Noam Hasenfeld made the music.

Christian Ayala did the sound design and the mixing on this episode. Melissa Hirsch checked our facts.
Thank you, Melissa.

And Jorge Just, Meredith Hodnott, Julia Longoria, Sally Helm, and Amy Padula are even better than the very best QVC clip.

Thank you to Brian Resnick, always, always, for co-creating the show with me and with Noam.

And thanks to Tracy Becker at the Southwest Research Institute in San Antonio, Texas, and to David Trilling at Northern Arizona University in beautiful Flagstaff, Arizona.

I appreciate both of you for taking the time to help me make sense of the universe. If you have thoughts on this episode or questions, please write in.
We are at unexplainable at vox.com.

And I would love to know, for example, if you have dreams about the moon or if you have ever turned into a werewolf.

If you want to support the show and help us keep making it, please join our membership program. It is at vox.com/slash members.

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You can also do us a big solid by leaving a nice rating or a review, or just by telling people in your life to listen.

Unexplainable is part of the Vox Media Podcast Network, and we will be back in your feed very soon.

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