Humans and every other living thing on Earth are perfectly suited to our wonderful planet. There’s life everywhere, from boiling-hot ocean vents to chilly mountain peaks. But what would life look like in other parts of the galaxy, or beyond? What would happen to our bodies if we lived in space?

In an out-of-this-world episode, Molly and cohost Jaxson moonwalk through the possibilities of life in outer space. They learn what scientists look for when they want to know if a planet or moon could support life. And they explore how science fiction can help actual scientists think about what alien life might look like. Plus, a spiffy new Mystery Sound!  

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INTERVIEWER 1: You're listening to Brains On, where we're serious about being curious.

VIOLET: Brains On is supported in part by a grant from the National Science Foundation.

DIANA SPANGLER: This is Captain Diana Spangler, reporting from the exploratory voyages of the Starship Brainiac. We have arrived at our destination to meet a group of extraterrestrial inhabitants who wish to form an exchange program with Earth. Their planet is named Big Bong Bloop. Lieutenant Martinez, is that correct?

LIEUTENANT MARTINEZ: Yes, Captain. The planet's atmosphere is so thick and foggy, you can't really see. So the creatures here have evolved to mostly communicate through sound or smell. The group we are here to meet appears to communicate in what we would call sound effects. They have enormous sensitive ears. So we should be careful about the noises we make.

DIANA SPANGLER: Ah, yes. We wouldn't want to accidentally offend anyone. Fortunately, we have our ambassador robot. Unit TR-307.


ROBERT: It's actually Robert, not Robot. Common mistake.

DIANA SPANGLER: Ah, yes. Well, Martinez, Robert, are you ready to meet the welcoming committee?


ROBERT: My sound effect vocabulary bank is fully loaded.

DIANA SPANGLER: Excellent. Here we go.



Extraordinary. Can you believe how different this is from Earth? I love this job.

LIUTENANT MARTINEZ: Wow. It is incredibly foggy on the planet's surface. I can hear all kinds of wildlife, but I can't see a darn thing. And there are so many different smells wafting through the air.

ROBERT: Captain, my sensors indicate that our hosts are approximately 20 feet in front of us.

DIANA SPANGLER: Thank you, Robert. Greetings, friends. Thank you for having us. We can't wait to learn more about you and your beautiful planet.

ROBERT: Translating.


They say, hello, and welcome. And--

Searching database. They invite you to waltz with them. It is tradition.


ROBERT: They wish for you to waltz. I will play a musical accompaniment.



DIANA SPANGLER: All in the name of the exploration. Here we go. 1, 2, 3, 1, 2--



ROBERT: Apologies, Captain. Their language contains nuances for which I was not prepared. They requested that you wrestle with them. Or is it wiggle?

DIANA SPANGLER: Robert, have you updated your software lately? Let's run that through the database one more time.

ROBERT: Database updated. The correct translation is whistle. They request that you whistle.

DIANA SPANGLER: Here goes nothing.



MOLLY BLOOM: You're listening to Brains On from APM Studios. I'm Molly Bloom, and my co-host today is Jackson from Todd County, Kentucky. Hey Jackson.


MOLLY BLOOM: So Jackson, you asked us a very cool question. Can you tell us what it was?

JACKSON: Yes. I wanted to know how people would evolve on other planets.

MOLLY BLOOM: So Jackson, it's such a cool question. What made you think of this?

JACKSON: I don't know.

MOLLY BLOOM: Do you like to think about space a lot?

JACKSON: Kind of.

MOLLY BLOOM: Kind of. When you think about this kind of thing, are you thinking planets in our solar system, or are you thinking planets we haven't even discovered yet?

JACKSON: Planets in our solar system.

MOLLY BLOOM: Do you have a favorite planet in our solar system?

JACKSON: Earth, I guess.

MOLLY BLOOM: Yeah, me, too. That's where I live. Would you like to travel to outer space if you could?


MOLLY BLOOM: How do you think it would feel to have that feeling you get when you're in a spaceship of that microgravity where you're floating around?

JACKSON: I think it would be really cool.

MOLLY BLOOM: What would be your favorite thing to try doing in microgravity?

JACKSON: A backflip.

MOLLY BLOOM: Oh yes. So today, we're talking about people in space. And--

JACKSON: Hey, Molly, is this peanut butter and jelly sandwich a part of the whole podcasting thing?

MOLLY BLOOM: Uh, what sandwich? Oh, hey, that wasn't there a second ago. I have one in front of me, too. What in the brown bag lunch is going on here?

ANNA GOLDFIELD: Oh, good. You found your sandwiches.

MOLLY BLOOM: Brains On producer Anna Goldfield. When did you put these sandwiches here? And why?

JACKSON: And how are they so delicious?

ANNA GOLDFIELD: Well, Jackson, I used fresh baked bread and homemade boysenberry jam. And Molly, I always bring props when I give a bread talk.

MOLLY BLOOM: A bread talk?

ANNA GOLDFIELD: You know, bread talks. We're all about building sandwiches to spark imagination. Using baguettes to understand the world. Spreading ideas, like jam on toast.


ANNA GOLDFIELD: I heard you were going to be talking about humans going into space. And I got so excited to tell you about my favorite pairing, humans and Earth. The peanut butter and jelly of things that need a peanut butter and jelly metaphor.

MOLLY BLOOM: I'm intrigued. Please continue.

ANNA GOLDFIELD: Well, like the delicious, nutritious PB and J sandwiches in front of you, humans and the planet we live on are a perfect combo. And that's because Earth has some really special stuff going on.

JACKSON: Like what?

ANNA GOLDFIELD: Well, for one thing, our distance from the Sun. We get just the right amount of light and heat from our favorite giant flaming ball of space gas. If we were closer to the sun, we'd get too crispy. If we were farther away, Earth would be a much chillier planet.

MOLLY BLOOM: That makes sense.

ANNA GOLDFIELD: There's also our atmosphere and oceans. Here, let me just flip the switch.



MOLLY BLOOM: Whoa, it's a perfect model of Earth attached to the ceiling. That was definitely not there before.

JACKSON: It even has clouds floating around it. How did you do that?

ANNA GOLDFIELD: A magician never reveals their secrets. Unless it's my secret recipe for plant-based Swedish meatballs. Anyway, our beautiful blue green planet has an atmosphere around it that not only gives us air to breathe, it also holds in heat. Like a giant Earth-sized coat. Other planets in our solar system have atmospheres, but none of them are quite like ours.

JACKSON: Maybe that's why no other planet in our solar system has humans. Or the amazing living things around us.

ANNA GOLDFIELD: Exactly. Every living creature on Earth has special characteristics that help them thrive in their environment. These characteristics are called adaptations.

MOLLY BLOOM: An adaptation can be a part of a living thing or something a living thing does to help it survive. They get passed down from generation to generation.

ANNA GOLDFIELD: Right. Us humans are perfectly adapted to Earth. We have lungs that can breathe the air, melanin in our skin that protects our skin from the Sun, and bones that help us withstand the pressure of Earth's gravity. Now, Jackson, can you reach under your chair and grab the little jar there? And Molly, there should be two more jars in your pocket.

MOLLY BLOOM: These pants don't even ha-- holy buttons, there are pockets on these pants now. With tiny jars in them. Incredible.

JACKSON: How'd you fit a cactus in this jar? It's so small.

MOLLY BLOOM: This jar has a tiny school of fish. And this one has a little flamingo. Anna, have you been tinkering with the shrinking machine again?

ANNA GOLDFIELD: What? No, no. Definitely not. These are actually perfect crocheted replicas of a cactus, a school of mackerel, and a flamingo. I made them last night while I was baking bread for your sandwiches. All of these living things are super different. But they look the way they do because they adapted to fit Earth's environment.

MOLLY BLOOM: Like humans. OK, I'm picking up what you're putting down. Fish have gills that let them take oxygen from the water. Flamingos have long legs so they can wade through the water.

JACKSON: And cactuses have lots of prickly spikes to keep other animals from munching on them.

ANNA GOLDFIELD: Exactly. Every species is different, but we all evolve to fit our planet. So Jackson, you wanted to know, how would humans evolve on other planets? Well, unless we could find one with conditions really similar to Earth, we just wouldn't be able to survive. It wouldn't be a good match. Like a peanut butter and spaghetti sauce sandwich.

JACKSON: You're not going to give us peanut butter and spaghetti sauce sandwiches, right?

ANNA GOLDFIELD: No. No, I for sure wouldn't do that. Also, not related to anything, don't look in the other desk drawer. There's definitely no PB and marinara sandwiches in there.

MOLLY BLOOM: So humans have evolved to be a perfect match for the conditions on Earth. And it would be really hard for us to survive on other planets. But there could still be other non-Earth life out there.

ANNA GOLDFIELD: Right. And there are scientists who are looking for these alien life forms.

MOLLY BLOOM: Yeah. They're called astrobiologists, and they're even looking in our own solar system. Like on Venus, where there might be tiny bacteria living in the atmosphere.

JACKSON: And the scientists think that it could be creatures living under the ice on Europa, one of Jupiter's moons.

MOLLY BLOOM: Even if there were living things on other planets or moons in space, they would probably look really, really different from anything we've seen on Earth.

JACKSON: Maybe they'd look like something we can't even imagine.

ANNA GOLDFIELD: Exactly. The possibilities are infinite. And that's why space is so amazing. Well, thank you both for coming to my bread talk. I'll see you guys later. I'm going to go play badminton with Bob. We call it bobminton. Bye.


JACKSON: Thanks for the sandwich.


MOLLY BLOOM: We've been talking about how Earth is a pretty good home for humans. But what if we wanted to visit other planets? Like a space vacation.

JACKSON: A space-cation.

MOLLY BLOOM: Yeah. And what if you could search a special website for the perfect space getaway?


NARRATOR: Airbnbnb. The third B is for Beyond. For when you want a little more space.


MOM: Planning this family trip has been such a hassle. Thank goodness for Airbnbnb.

DAD: Yeah. Without that the Air, Bed, and Breakfast and Beyond website, I don't know how we'd choose the perfect spot for our space-cation. Let's see. Oh, what about Mars?

KID 1: Dad, there's hardly any oxygen in the atmosphere. Is there even water there? How will we shower? Gross. What about a moon instead of a planet? They're so much more exclusive.

KID 2: Yeah, let's go to Europa. The gravity there is super low. Mom, I could jump so high at the beds there. I bet I could even dunk a basketball.

KID 1: Yeah, I heard it probably has an ocean. I could do a beach vacay.

MOM: That's Jupiter's moon, right? Let's take a look.


Oh, but it's so cold and icy. It looks like the ocean would be trapped under a thick shell of ice. No, I want some place warmer.

DAD: How about Venus? Looks like a balmy 800 degrees Fahrenheit on the surface. That hot enough for you, hun?


I'm funny.

KID 1: Why are we even looking in space? All of these places are going to freeze us or squish us or explode us out of a space volcano.

MOM: Maybe we should just visit Aunt Edna in Maine again and save the space-cation for another time.

NARRATOR: Airbnbnb. Space will take your breath away. No, really. There's no oxygen up there.


MOLLY BLOOM: We've been talking about space, but now it's time to make some space for the--


AUDIO TRACK: Mystery sound.

MOLLY BLOOM: Are you ready for the mystery sound, Jackson?


MOLLY BLOOM: All right. Here is the sound.


What do you think that sound could be?

JACKSON: A cricket.

MOLLY BLOOM: What made you think it's a cricket?

JACKSON: Because it has that [RATTLES] sound.

MOLLY BLOOM: Very, very good guess. Well, we'll get another chance to hear it, guess, and get the answer right after the credits, so stick around.


Hey, friends. We're working on an episode about birthdays, and we want to hear from you. We all know the birthday song. It's great. It's everywhere. But imagine it was your job to come up with a new song to sing to everyone on their birthdays. What would that song be? Jackson, what would your new birthday song be?

JACKSON: Happy birthday, and then the person-- happy birthday, and then it's the person's name. Happy birthday, happy birthday, happy birthday to you. Something like that.

MOLLY BLOOM: Oh, I like that one. So if it were you, what we're saying is happy birthday, Jackson. Happy birthday, Jackson. Happy, happy birthday to you. Like that?

JACKSON: Yeah. Yes.

MOLLY BLOOM: I like it. The current birthday song, you only say the person's name once. But this would really emphasize the birthday kid. Good idea. Listeners, we want to hear your new birthday songs. Record yourself and send it to us at While you're there, you can also send us mystery sounds, drawings, high fives, and questions.

JACKSON: Like this one.

INTERVIEWER 2: Why are elephants so big?

MOLLY BLOOM: You can find an answer to that question on our Moment of Um podcast. It's a daily dose of facts and curiosity you can find wherever you listen to Brains On. Again, that's

JACKSON: And keep listening.

You're listening the Brains On. I'm Jackson.

MOLLY BLOOM: And I'm Molly. And we're thinking deep thoughts about deep space. Specifically, how humans would evolve on other planets. We just heard that humans are perfectly adapted to live on Earth. Like peanut butter is perfectly suited to go with jelly.

JACKSON: That makes it hard for us to live on other planets. But what if we lived on a giant spaceship headed towards another galaxy? Or if we set up a base on the Moon? Or Mars?

MOLLY BLOOM: So even though we don't know for sure what it would be like for us to live in outer space, we can get some clues from real life people who have been there-- astronauts.

JACKSON: Since space is so different from Earth, it does things to our bodies.

SCOTT SOLOMON: So first of all, we know that some of the things that are really different if you are on Mars or anywhere that is beyond Earth out in space, some of the biggest changes are, first of all, gravity.

JACKSON: That's Scott Solomon. He hosts a podcast for kids called Wild World, all about what it's like to be a scientist in different places on Earth.

MOLLY BLOOM: He's also a biologist at Rice University in Texas. And he says studying how space affects astronauts' bodies can help us understand what humans might look like if we started living in space.

SCOTT SOLOMON: What we do know is that for people that go into space for shorter amounts of time, so astronauts that have spent a year out in space on the International Space Station, there are several things that happen. One is that without the force of gravity pushing down on their bodies, their bones and their muscles become weaker. And that is something that astronauts are constantly having to work against.

MOLLY BLOOM: Astronauts have to exercise in space for around two hours every day to make sure their bones, muscles, lungs, and heart stay strong. Next time I hop on my exercise bike, I'm going to pretend I'm biking past Mars.

JACKSON: Living in space also affects our immune system, which is our bodies' built-in burglar alarm for fighting off viruses and infections. That sometimes makes it a little easier for us to not get sick.

SCOTT SOLOMON: But most of those are changes that pretty much go away after they come back to Earth. So their bones and their muscles get strong again once they're back on Earth and experiencing Earth gravity. Their heart gets stronger again. And their immune system kicks back into gear.

But it would be pretty different for people living out in space or living on Mars.

MOLLY BLOOM: The only people who have been to space. So far are adults. So we don't yet know how kids' bodies might change, or how someone's body might look if they were born in space.

JACKSON: Whoa, space babies.


MOLLY BLOOM: Yeah. Scott says babies born in space might look pretty different from Earth babies, especially after many generations up there.

SCOTT SOLOMON: What you might get is very tall stretched out people. Very spindly arms and legs. Because that's what happens to astronauts. They actually come back to Earth a little taller, several inches taller, than when they left. Because the spaces between their spine, the bones in their backbone, get elongated when gravity is not pushing down.

JACKSON: Maybe future humans will be eight feet tall and live in space with their long needle-y arms. Note to self-- invent space basketball.

MOLLY BLOOM: Ooh, I'd watch space basketball. Growing up traveling through the galaxy sounds so cool. You could write letters to pals at a space station on your space stationery.

JACKSON: Yeah. Out there, every walk you take is a space walk.

MOLLY BLOOM: Every shower is a meteor shower.

JACKSON: And every scarf you knit is a spacecraft.

MOLLY BLOOM: Yes. So far, we've talked about how our human bodies might change and evolve in deep space.

JACKSON: But what about other lifeforms? Are there aliens perfectly suited to their alien planet? And what would they look like?

MOLLY BLOOM: We decided to ask Steve Howell, an astrophysicist at the NASA Ames Research Center.

STEVE HOWELL: Are we the only life in the whole universe? I think most of us would say not. But we have found no other life yet. And so astrobiology is a field where people are trying to figure out, what would we look for? What would be the signatures of life? Where would we find it? What planets would have life and what planets wouldn't?

MOLLY BLOOM: Steve's whole job is to try to answer these questions. He studies exoplanets. Those are planets outside of our solar system very far away from Earth that orbit other stars.

JACKSON: And he's helped build special telescopes that could take pictures of these planets. These telescopes are big, like the size of a car big.

MOLLY BLOOM: Steve uses these telescopes to look at exoplanets thousands of light years away to figure out whether they might be able to support life.

JACKSON: One way he does this is by looking for planets similar to Earth.

MOLLY BLOOM: Planets with a similar size and mass as Earth are more likely to have an atmosphere like ours. That means they might even have water like Earth and be able to support life.

STEVE HOWELL: So I think the estimate is planets as small as the Earth that might orbit their star where their temperature on their surface is like us, there might be 20 billion of those in our galaxy alone.

JACKSON: Whoa, 20 billion Earths? Billion with a B?

MOLLY BLOOM: Yep. They haven't found a world exactly like ours yet. But there's a really good chance that if there is alien life out there, it's on one of these Earth-like planets.

JACKSON: But scientists think they're probably living in much harsher conditions than we do.

MOLLY BLOOM: So to learn more about how aliens potentially survive, they're studying creatures on Earth that live in extreme environments.



JACKSON: Even though they're extreme, that doesn't mean they like to jump out of planes or snowboard down mountains.

STEVE HOWELL: There's these things called extremophiles, and they're usually little tiny animals. They live in very extreme environments. Places that humans could not live. So it's very hot or it's very acidy or very cold.

MOLLY BLOOM: Extremophiles are found all over the world. And even though they're usually pretty small, they're hard core.

CJ: I'm CJ.

JC: And I'm JC.

CJ AND JC: And we're two bacteria who live to get extreme.


JC: You'll find me in the steaming hot soil around a volcano eating toxic heavy metals. And of course, listening to heavy metal music.

CJ: Oh yeah. I'm hanging ten at the bottom of the ocean miles below the seafloor buried inside of a rock. Talk about high pressure environment. Who needs oxygen anyway? Or light for that matter.

CJ AND JC: We're CJ and JC, and we're two bacteria who don't do anything unless it's extreme.


MOLLY BLOOM: Based on what they know about life on Earth, many scientists believe that alien life out there probably looks a lot like these microscopic creatures. So if we can understand how an animal that lives in a super, super cold environment lives and evolves on Earth, it can help us understand how life on a super, super cold planet could evolve.

JACKSON: But when it comes to knowing what exactly aliens could look like, that's a question that scientists can't answer yet.

MOLLY BLOOM: So we asked you to dream up how alien life might greet us if we found them on another planet someday. And here's what you came up with.


SUBJECT 1: I imagine an alien or creature on a different planet and how they would say hi would be boogie.

SUBJECT 2: I think they would walk up to each other and touch noses and wiggle them.

SUBJECT 3: They would say zoing groing and wriggle around.

SUBJECT 4: I think an alien would greet me by slapping its knees and then making an X across its chest.

SUBJECT 5: I think the alien would look at me weirdly, change the mood, and then go-- [TONGUE NOISES].

MOLLY BLOOM: A big [TONGUE NOISES] to Sydney, Evie, Violet, Sanvi, and Hank for sending in those awesome ideas.



MOLLY BLOOM: Imaging life on other planets is something that Mike Brotherton does a lot. He's a science fiction writer and an astronomy professor at the University of Wyoming.

JACKSON: And he uses actual space science to dream up realistic aliens.

MIKE BROTHERTON: If you're going to put your story in space on an alien world, the reality is really cool. You don't have to make stuff up. And there are a lot of things that, if you understand the science, it creates opportunities.

MOLLY BLOOM: Mike wrote a story set on a real exoplanet called Kepler-42 b.

JACKSON: Kepler-42 b doesn't rotate like our Earth. Instead, it has a bright side and a dark side. Like on our moon.

MOLLY BLOOM: The bright side is very hot, because it gets all the light and heat from the star it orbits. The dark side is cold and frozen all the time.

JACKSON: So Mike had to dream up a creature that could exist on this very real exoplanet.

MIKE BROTHERTON: Yeah. So the aliens in the story are called twills. And as I recall, that was inspired by the idea that they would live in twilight. The middle ground between the dark side and the bright side. If you want enough sunlight for vegetation, you need to be in a place where water is maybe less common, more of a desert. If you want to get to the water, you have to go closer to the dark side. They might need to migrate.

MOLLY BLOOM: And once he figured out where his fictional alien creatures would live on this exoplanet, Mike imagined what they would look like.

MIKE BROTHERTON: The twills are six-legged, low down to the ground. And large enough that like camels, they can carry a lot of water with them. And so they don't have to drink for extended periods. They'll migrate to water sources when they need to.

JACKSON: Whoa, six-legged camels? Those sound like some strange looking aliens.

MOLLY BLOOM: Well, if something like the twills are out there, we might look pretty strange to them, too. There are a lot of unknowns when it comes to life in outer space. And scientists haven't found all the answers yet.

JACKSON: But science fiction helps us imagine how life evolves and adapts to the conditions on other planets, just like it did here on Earth.


MOLLY BLOOM: Human beings evolved over millions of years to be perfectly adapted to our home planet, Earth.

JACKSON: What we don't know is how humans might look if they evolved on other planets.

MOLLY BLOOM: But we can look at how space affects astronauts' bodies for clues.

JACKSON: Scientists are also studying tiny creatures on Earth that live in extreme environments to imagine what life on other planets might look like.

MOLLY BLOOM: And some people are using science fiction to imagine life on other planets.

JACKSON: Which is pretty cool, if you think about it. After all, people used to think that space travel was the stuff of science fiction, too.

MOLLY BLOOM: Humans are pretty great at making what they imagine a reality. I'm just excited to see what we think up next.

JACKSON: And that's it for this episode of Brains On. This episode was produced by Anna Goldfield, Molly Quinlan, Molly Bloom, Rosie DuPont, Arome Urdaslawsi, Anna Weggel, Nico Gonzalez Wisler, Ruby Guthrie, and Marc Sanchez.

MOLLY BLOOM: Our editors are Sanden Totten and Shahla Farzan. This episode was sound designed by Rachel Breeze, and we had engineering help from Jon Nicolosi and Derek Ramirez. Beth Perlman is our executive producer. The executives in charge of APM Studios are Chandra Kavati, Alex Shaffert, and Joanne Griffith. Special thanks to Heather Reed, Jade, Brandt Miller, Koko, and Lulu.

JACKSON: Brains On is a nonprofit public radio program.

MOLLY BLOOM: There are lots of ways to support the show. Head to

JACKSON: While you're there, you can send us your questions.

MOLLY BLOOM: And you can subscribe to our Smarty Pass.

JACKSON: Ad free episodes and bonus episodes for you.

MOLLY BLOOM: All right, Jackson, my friend, are you ready to listen to that mystery sound again?


MOLLY BLOOM: All right, let's hear it.


All right, Jackson, what do you think?

JACKSON: I still think it's a cricket or a grasshopper. Or maybe it's a cicada.

MOLLY BLOOM: Very good guess, Jackson.

JACKSON: I'm going to guess cicada.

MOLLY BLOOM: OK. Are you ready for the answer?


MOLLY BLOOM: All right, here is the answer.

CHARLIE: Hi, my name is Charlie, and I'm from Ellicott City, Maryland. And the sound you just heard was a damselfly flapping its wings. I made this sound by touching damselflies. And they make that cool flapping noise. Did you know, damselflies and dragonflies are different? Damselflies put their wings down, and dragonflies kick them up.

MOLLY BLOOM: Jackson, amazing work. It was not quite a cicada, but it was an insect flapping its wings. It was a damselfly.


MOLLY BLOOM: So nice work.


Now it's time for the Brains Honor Roll. These are the incredible kids who keep this show going with their questions, ideas, and mystery sounds, drawings, and high fives.



AUDIO TRACK: Brains Honor Roll. High fives.

MOLLY BLOOM: We'll be back next week with more answers to your questions.

JACKSON: Thanks for listening.

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