[AUDIO LOGO] FLORA LICHTMAN: Hey, I’m Flora Lichtman, and you’re listening to Science Friday. Today in the show, an attention-hogging, larger-than-life celebrity that everyone, and I mean everyone, seems to be talking about. Comet 3I/ATLAS. This

Dirty snowball is a visitor from another solar system, and it’s only the third interstellar object we’ve ever found. And today, today, it’s closer to us than ever before, a mirror 170 million miles away. So naturally, space nerds like my next guests and me are really excited about this.

But 3I has permeated the astrophysicists’ bubble and captured the spotlight in a way that I think maybe no other big hunk of rock ever has. We will talk about that too. Here to dish about this interstellar luminary are my guests, Doctor Stefanie Milam, an astrochemist at NASA who studies comets and interstellar objects, and Doctor Hakeem Oluseyi, an astrophysicist who runs the Astronomical Society of the Pacific. Stefanie, Hakeem, welcome back to Science Friday.

STEFANIE MILAM: Thanks for having me.

HAKEEM OLUSEYI: Yes, thank you.

FLORA LICHTMAN: Stefanie, I know interstellar objects are your jam. How pumped are you right now?

STEFANIE MILAM: Super excited. This has been a whirlwind of a year since the discovery in July, and we are getting amazing data from telescopes on this object and learning more and more each and every day about its origins, where it’s from, and comparing that to objects in our own solar system.

FLORA LICHTMAN: I want to drill into that in a second. But, Hakeem, you’re more of a space generalist. Does this rise to the same level of excitement for you?

HAKEEM OLUSEYI: Oh, it definitely does, and I’m just impressed with the field. It just keeps giving, from images of supermassive black holes at the cores of galaxies to gravitational waves of black holes colliding to, now, interstellar objects coming into the solar system. It just doesn’t stop. It’s awesome.

FLORA LICHTMAN: Can’t stop, won’t stop. Stefanie, what answers are you trying to get while 3I is closest to us?

STEFANIE MILAM: We’re mostly studying the composition of this object right now. We want to know what it’s made of and what clues we can get about where it came from based on that composition. So we’re seeing what different molecules are there and what abundances they have, which tells us a little bit about the chemistry of the planetary system that it was formed from.

But we’re also looking at things like isotope ratios, which are the heavier forms of any given atom because those are actually from either the primordial Big Bang or are formed in stars of different masses and ages. And that actually tells us about where in the Galaxy some of these molecules could have formed and how that has then been preserved in this interstellar object.

FLORA LICHTMAN: Hakeem, what do you want to about this object?

HAKEEM OLUSEYI: Well, what really excites me about these interstellar objects is the fact that we’re getting samples of other star systems. When a star forms, it forms as a part of this more massive structure that has a star at the core and a disk that will eventually form planets. And in that process, you build up these cometary bodies. You end up with asteroid-like objects.

And every star has a different history. And every cloud that they form from, they have different chemical abundances. So when a person, like Stefanie and her team, they look at the light and figure out what this comet is made of, we’re getting an understanding of the variations that can exist in these various forming planetary systems.

FLORA LICHTMAN: The diversity of solar systems, it sounds like.

HAKEEM OLUSEYI: Exactly.

FLORA LICHTMAN: Stefanie, I know we’re trying to get James Webb to take a look at this. What can go wrong?

STEFANIE MILAM: So good news, we are looking at it with the James Webb Space Telescope. We got new data just yesterday–

FLORA LICHTMAN: (WHISPERS) Yes!

STEFANIE MILAM: –with one of our instruments on board. And we’re expecting to have more data next week, so hopefully I get a good Christmas present. The challenge is that we have right now for observing this object with the James Webb Space Telescope is we have to know precisely where in the sky this object is to point the telescope at the exact position that it’s at.

This is challenging because it’s moving. It’s flying across our solar system. It just passed the Sun, so it’s nice and ramped up in its activity.

And that makes it very challenging for us to see where exactly it is in the sky with respect to known stars so that we can take the James Webb Space Telescope, which is designed to look at the farthest galaxies of our universe– so it has this really tiny little window that we can actually peek through. And we have to make that little tiny window fit right on top of this interstellar object. So we’ve been using telescopes all over the world to try to really hone in on where it is in the sky so that we can make sure we don’t miss it with the James Webb Space Telescope.

FLORA LICHTMAN: This sounds stressful. I’m stressed.

STEFANIE MILAM: Yeah. My entire team is on the edge of our seats. We’ve reached out to all of our colleagues at every telescope, asking them, begging them to get as much data as they possibly can to help us refine this orbit and make sure that we can actually do the observations that we really want to do next week and can really put the beacon on this object in the way that we want to.

FLORA LICHTMAN: We have to talk about aliens because there have been all these alien theories about 3I/ATLAS. I’ll ask you both, but in your view, what are the chances that this is an alien craft?

STEFANIE MILAM: This looks like a comet. There is no evidence that we’ve seen to date that there is anything atypical about the composition, the activity or any other phenomenon. So far, nothing has come up as an extreme that can’t be explained by our regular physical processes that we see in comets in our own solar system.

HAKEEM OLUSEYI: Yeah, there’s nothing that says that this is alien. But I’ll say this, there are aliens, and there are aliens.

FLORA LICHTMAN: Yes.

HAKEEM OLUSEYI: So as astrobiologists study the origin of life and where life could possibly be in various niches in the universe, one idea, which is wild and highly unlikely but it is still not completely ridiculous, is that comets could possibly hold microscopic life forms. We’ve already found a lot of complex biological molecules on comets.

So if you’re talking about microbial life, hey, there’s a tiny probability that there might be something like that. But if you’re talking about the Klingons or the Ferengi or an alien civilization, I think the probability is vanishingly small.

FLORA LICHTMAN: Hakeem, is there any teeny tiny little part of you that feels disappointed?

HAKEEM OLUSEYI: No.

FLORA LICHTMAN: Not even a smallest corner of your heart?

HAKEEM OLUSEYI: Well, so to be disappointed, the expectation has to be there, and I never had the expectation in terms of an alien craft because there are a lot of assumptions that go into that. Anytime you see an alien depicted in fiction and they’re kind of human like, that means that they were a primate that evolved in the canopy of trees somewhere. What’s the probability of that?

It’s not happening. That is what humans would do. And my general smell test for anything that is said to be alien is how similar is it to humans.

And if it’s similar in any way, then it’s projection. You’re not letting the data tell you the story. You’re projecting your hopes and dreams onto it.

STEFANIE MILAM: I think Hakeem’s right. We want to find life out there. We want to know if we’re alone. We want to knwo how did we get here.

We’re trying to find the ingredients for biology. So we want to know, are there structures like RNA or DNA out in space? We’re getting close.

We’re finding amino acids. We’re finding sugars. We’re finding molecules that we find that life is comprised of. And so that’s very intriguing. We’re pushing as hard as we can, and technology is taking us one step closer every time we have a new observatory or a new facility that’s enabling us to look even harder.

FLORA LICHTMAN: Look, on a philosophical level, this is what I want your take on. We know that science is about challenging assumptions, being open to outside-the-box answers. Why does the questioning around this being alien craft rile up the scientific community?

HAKEEM OLUSEYI: Oh man. There are cultural issues. I think we’re best when we are open-minded skeptics. I do think we do have to keep an open mind.

I’ve seen a lot of cases over the duration of my own career, where you have some new observatory and someone makes an observation or an experiment and they report their results. And the scientific community says, hey– even though they’ve never observed this phenomenon, they say, hey, we know how this really works.

We’ve calculated it. And what you observe does not match. Therefore, there’s something wrong with your observatory or your experiment.

FLORA LICHTMAN: This goes against conventional wisdom, and thus it is wrong.

HAKEEM OLUSEYI: Exactly, exactly. So, no, I’m completely open minded. I listen to the craziest people. [LAUGHS] But I bring my rigor, my scientific rigor, and skepticism along.

So do I think that there’s life out there? I think it’s probably almost certain. But when you get to the level of civilization and technology, that’s when the probabilities absolutely plummet. So that is not what I’m expecting, but I am expecting life. But not necessarily in this comet.

[LAUGHTER]

FLORA LICHTMAN: Setting aside the alien theories for a second.

HAKEEM OLUSEYI: Yes.

FLORA LICHTMAN: This comet has gone viral, which I think is awesome, personally. I love to see it. And I’m wondering if you take any meaning from that.

HAKEEM OLUSEYI: Oh, I do. I think that the sizzle around this comet, even if it’s about aliens, is a good thing. I think that it is bringing more curious minds to wondering about nature.

And personally, my on ramp to being a scientist in my youth included exploring the paranormal, exploring ghost stories and bigfoot and those sort of ideas. They live in a similar part of the soul and mind, that part of curiosity, exploring the unknown, going for that which is really weird and different. And I think that the attention that astronomy is able to generate, which leads to people becoming a part of this enterprise, and this is on ramp that gets us there. So I’m all for it.

FLORA LICHTMAN: Well, bon voyage 3I/ATLAS, and good luck, Stefanie. We can’t wait to hear what you find out. Doctor Stefanie Milam is an astrochemist at NASA who studies comets and interstellar objects. Thank you for being with us today.

STEFANIE MILAM: Thank you so much for having me.

FLORA LICHTMAN: Hakeem, can I hold on to you for one more second?

HAKEEM OLUSEYI: Yes.

FLORA LICHTMAN: We have a listener with a space question, and I’m wondering if you can help.

HAKEEM OLUSEYI: I’ll try.

FLORA LICHTMAN: We’re going to hear it right after this short break. Don’t go away.

[MUSIC PLAYING]

Hey, it’s Flora just reminding you that Science Friday has dollar-for-dollar donation match right now, meaning that if you make a donation today through December 31, it will be doubled. So now is the time to head over to sciencefriday.com/support and make a gift. Our 2026 programming depends on your support. That’s sciencefriday.com/support, and thank you.

[AUDIO LOGO]

OK, here’s some of that conversation.

AUDIENCE: My name is Michael, and I’m calling from St. Louis. My question is, why has the United States and the other countries involved decided to simply throw away the International Space Station by letting it crash into the Pacific Ocean when there are so many imaginative things that might happen if we did something else, like turn the thing loose into deep space?

There’s so many thrusters on that thing that they could shoot it off into the great unknown and just let it go. To just throw it away like you’re putting it in the recycling bin, it just doesn’t make sense.

FLORA LICHTMAN: What do you see as the advantage of letting it go into the final frontier?

AUDIENCE: If some other civilization, if they find it and investigate things about it, questions like, where’s this from? Why is it uninhabited? What was its purpose?

And was it intentionally set free from somewhere? Or did it escape? Or did someone lose a war or what?

FLORA LICHTMAN: Forget the golden record. We have a whole home we can send into space.

AUDIENCE: Exactly, exactly.

FLORA LICHTMAN: You see this as an act of generosity to aliens.

AUDIENCE: I suppose it is. But I was thinking of it more of an act of a gift to the artists and musicians and poets of the world, who would think about this thing just cruising off into whoever knows where.

FLORA LICHTMAN: The poets on Earth, the Earthlings, the Earthling poets.

AUDIENCE: Oh yeah. Right, right.

FLORA LICHTMAN: This is a gift to our imagination, actually, is what you’re saying.

AUDIENCE: Yes, to our imagination. Yes, yes, and to the scientists of the foreign universes and galaxies yet to be discovered.

FLORA LICHTMAN: OK, well, I want to look into that, if that’s OK.

AUDIENCE: I’m with you.

FLORA LICHTMAN: Why I do some work and then report back?

AUDIENCE: That would be delightful.

FLORA LICHTMAN: Hakeem, OK. I am sure that there are a million and one reasons not to send the ISS out into the great unknown, but can we at least agree that listener Michael has a point here, that this is a romantic option?

HAKEEM OLUSEYI: Oh, if it were only so simple. It is a romantic option. And what’s also a romantic option? Just leaving it where it is in orbit. But even that is far too expensive and dangerous.

FLORA LICHTMAN: Walk me through it. What are the practical reasons for crashing it into the sea, as opposed to leaving it out in space or sending it into the great unknown?

HAKEEM OLUSEYI: You have three options, really. So there are what are called graveyard orbits. You boost it up to a higher orbit, and it pretty much just stays there orbiting.

And even that is too expensive. It’s a lot of mass to move. And because of that, it just is prohibitive. And then once you get there, it becomes a debris risk.

Another option is doing nothing. And in that case, it’s going to de-orbit naturally. Anything in low Earth orbit tends to come down for various reasons. And in that case, it could land on someone. It could land on a crowd of people. You don’t want to have an uncontrolled de-orbiting.

So the third option is a controlled de-orbiting. And that is the option that NASA has selected. That’s the least expensive and the safest. It’s balancing all things.

FLORA LICHTMAN: Is Michael right technologically that you just– it has thrusters on it. You just turn them on and let them him go for as long as they go, and then it’s out on its way.

HAKEEM OLUSEYI: No, that is not– there are thrusters, but they aren’t designed to move the entire Space Station as it is currently assembled. And it wasn’t designed to even last this long, and it certainly wasn’t designed to last indefinitely.

And a de-orbit acceleration kick as a complete body, it’s big. So you have to get fuel to it. You got to slap rockets on it.

You would have to model that mechanically to understand how to do it, and that’s going to cost you millions of dollars. Then when you get to the point of actually trying to do it, that’s going to cost you definitely billions, if not hundreds of billions of dollars. And then you’re going to have astronauts and potentially cosmonauts involved. So you’re putting human lives at risk.

So there is no real compelling reason to send it out. It’s a, it would be nice if, if we had infinite money and infinite resources, oh, yeah, let’s undertake this massive task of making that happen. It’s worse than building a pyramid. It’s really, really challenging.

FLORA LICHTMAN: So you’re telling me there’s a chance.

HAKEEM OLUSEYI: [LAUGHS] Well, here’s the thing, if we get that asteroid Psyche that is made up of all the precious metal is worth more than $1 quintillion, yeah, maybe we could make it happen.

FLORA LICHTMAN: Doctor Hakeem Oluseyi is an astrophysicist and CEO of the Astronomical Society of the Pacific. And if you, like Michael, have a burning question for us or maybe an outside-the-box idea, We want to hear it. Leave us a voicemail at 877-4-SCIFRI, and we’ll look into it.

This episode was produced by Rasha Aridi. Thank you so much for listening. Happy Friday. I’m Flora Lichtman.

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