Short Wave - Should Humans Live On Mars?

Episode Date: April 21, 2025

As global warming continues and space technology improves, there is more and more talk about the growing possibility of a sci-fi future in which humans become a multiplanetary species. Specifically, that we could live on Mars. Biologist Kelly Weinersmith and cartoonist Zach Weinersmith have spent four years researching what life on Mars would look like if we did it anytime soon. In their book A City On Mars, they get into all sorts of questions: How would we have babies in space? How would we have enough food? They join host Regina G. Barber and explain why it might be best to stay on Earth. Check out Kelly and Zach Weinersmith's book A City On Mars.Have another space story you want us to cover on a future episode? Email us at [e-mail] — we'd love to hear from you! See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. So there's a sci-fi fantasy that as an astrophysicist and a trekkie, I've been watching percolate all my life. And in the last decade, it feels like it's become more than fantasy. Strap yourselves in. We're going to Mars. Not just a few astronauts, thousands of people are going to colonize Mars. And I am telling you that they're going to do this soon.

I would love to see, you know, a truble. trillion humans living in the solar system. Now the next Mars launch window opens in 2026. At the rate we're going here, you wouldn't rule out seeing some sort of mission there in a couple of years' time. Some of you will end up working on projects on Mars, and I guarantee that some of your children will end up living there. One path is we stay on Earth forever, and then there will be some eventual extinction event.

The alternative is to become a space-franc civilization and a multi-planet species. But I've always wondered, what would a space colony actually look like? So the vision for a successful space settlement would require that you have essentially families living on the surface of Mars and that those people are able to have careers that, you know, give them the money that they need to sustain themselves and that they're also able to have children. And those children can successfully grow up and have their own children. That's Kelly Weiner-Smith. She's a biologist and science writer.

And she and her partner, Zach Weiner-Smith, spent four years. researching space settlement for a book called City on Mars. And in it, they get into everything it would take to do this. They talk about the key real estate. The moon, Mars, we're creating an orbital space station, and among those Mars is overwhelmingly the best option. How we might do all the nitty-gritty of daily living. Can human adult bodies survive on the surface of Mars?

Can we safely have babies on the surface of Mars? How do you govern these communities? So, like, whenever someone talks about going to Mars on, like, Twitter, they post a gif of a guy walking toward the horizon dramatically. But most of life in the International Space Station is like scrubbing the toilets and making sure there's not too much mold and cooking dinner and that sort of thing and managing interpersonal relationships. It's a lot like Earth.

And so we need to have the solutions we have on Earth. So today on the show, we do a little thought experiment. What would it really take for humans to live in space and specifically on Mars? Can we do it in our lifetimes? And more importantly, should we? I'm Regina Barber, and you're listening to Shortwave, the science podcast from NPR. Okay, so it feels like people's settlement obsession is mostly focused on Mars. Why is Mars the big candidate?

Well, space is huge and Mars is relatively close. It has a lot of the things that we would need to be able to grow plants and keep humans alive. It's still a harsh environment, but, you know, the moon, for example, is very pouring carbon. And as carbon-based life forms, we need that. and Mars has a lot more of that. Mars also has plentiful water that's not too hard to get. And it's just sort of easier to get to than a lot of other places in our solar system. Okay, let's start with the first hurdle, which is like keeping people alive in space for a significant amount of time.

The longest someone has been in space is like just over a year. That's not a lot of data for us to have for long-term effects of people in space. What do we know about the dangers of living outside of Earth's protective magnetic field, like on the human, and body. Sure. So, you know, when you're in an orbital space station, you are under the influence of Earth's gravity, but you experience, like on a roller coaster, zero gravity. This reliably produces all sorts of terrible stuff for the body. The obvious stuff is loss of bone mass, which happens at a very rapid clip. A steady show about 1% bone loss in the hip per month. I want to emphasize per month. You may ask yourself why we don't turn into like Harry Potter when the bones

got dissolved and no one has been up for more than 437 days. That was the maximum time. Only a few people have been up for a year. Muscles experience very similar effects. People often get motion sick right when they get up. They also lose what's called the Barrow Reflex, which is that thing where you go from lying down to standing up and you get a little dizzy. That can happen in space so that when you get back to Earth,

it's considered very impressive if you can merely walk after a few months. more subtle effects are things like higher rates of certain bacterial infections that we don't experience on Earth. It might be due to distress, might be due to the zero-gravity allowing bacteria to just kind of float around. And then somewhat especially worryingly is that you reliably experience vision loss and we don't know why. And this happens even on short trips. The best version of this is that we lose some vision and you have to send up what are called space adjustment goggles, or glasses rather. The scary version is that there's some broader nerve damage that we don't understand yet

that could cause cognitive effects if people were up in space longer. Right, but this is, this is, you know, a different acceleration due to gravity in orbit versus on Mars. That's exactly right, yeah, and that's important. So there's some world in which 40% Mars gravity makes things just fine. Like one of the things we worry about is having babies in space, and, and, and, zero gravity, you try to imagine like kids not developing bones normally.

Maybe 40% gravity is enough to make the body work out or maybe there's even some world in which you wear like a weighted suit and that's enough to handle it. But we don't know is the problem. Let's talk about radiation. So like when we have, you know, the ISS, we have

some amount of protection from the magnetosphere of Earth. But now we go to Mars or even the travel to Mars. That protection is gone. So what does that mean for settlements outside of Earth? You know, I think the honest answer is we don't really know. And it's worth noting that space radiation is different than the kinds of radiation we typically

encounter on Earth. So we don't have a lot of good Earth-based data on this. But the astronauts in the space station are pretty much not experiencing it or they're experiencing much less of it. And they're not out there for very long. So when you're en route to Mars, which is a trip that takes a minimum of six months, given current technology, you have some shielding from your spacecraft, but probably not quite enough. And then when you get to Mars, you're still exposed to a lot of it because Mars doesn't

have a strong planet-wide magnetosphere like we've got on Earth, and the atmosphere is only 1% as thick as what we have on Earth, so most of that radiation hits the surface. And most of the proposals that we've seen involve burying our habitats under a few meters of the dirt on Mars to try to protect us from that radiation. So none of those beautiful glass habitats that maybe you've seen in artist renditions, we're living like mole people underground. Okay, okay. Another question. beyond the mold people. Like, what do we know about how, like, people eat? Like, how are they going to get enough food?

Are they going to produce that food? Are we going to send it all? Initially, we're going to send a lot of it, for sure. Like, when we're doing the first sorties, which is when people, you know, go, stay for a little while and then come right back and don't plan on spending the rest of their lives there, that will probably mostly be things like freeze-dried food. But when we're going to have settlements there, we're going to need to be able to grow food there. And that's going to be difficult because the regoliths, so, like, the dirt on the surface has perchlorates in it.

These are endocrine disrupting hormones which mess with metabolism and adults and fetal development for children. And we know that when you grow plants in the presence of perchlorates, the plants pull the perchlorates into the tissues. So we're going to have to make sure that we're getting those perchlorates out of the dirt and out of the water. And maybe we'll need to do hydroponics where you're not using that dirt at all. And it's going to be hard to bring protein also. So most of the proposals we've seen state that you can't bring like chickens or cows. They're just they're too big. They're too messy.

They're too hard to keep alive. Oh, my God, I hadn't even thought of that. Yeah, and so a lot of them for protein, it's like, well, you either have to be a vegetarian or you need to be comfortable with insect as a protein source. Oh, yeah. Easy. I've got to admit it's not for me. Wow.

Let's talk about babies, because you've brought it up a few times. Let's say we can keep somebody alive for 20 plus years on the surface of Mars. Then we see them possibly reproducing. Yeah. Often when this question comes up, if it comes up at all, it's like, can you have a baby in space. And the answer might well be yes. A bigger, trickier part is can they develop to an age where they can have babies? Can they go through all the stages of development in this foreign environment? Gestation, birth, becoming teenagers, all this stuff. You know, Kelly mentioned the

perchlorates on the surface, they disrupt hormones. Yeah. Right? And there's a bunch of subtle stuff that we haven't got into. Like, if you go to the ISS, the atmosphere is very high in carbon dioxide. Orders of magnitude more than on Earth, we can tolerate it. But astronauts often complain of headaches. Many other chemicals are going to be at different concentrations that we have on Earth. This is the tip of the iceberg. You may have the idea that space stations are kind of like organized projects for answering questions, and they aren't. They're done for political reasons, and scientists get to throw experiments at them. So we have like a grab bag of experiments on reproduction in space. Some invertebrates, some vertebrates, a very small number of like rodent

studies, nothing even close to a human. And what we really need is like a general. generational steady on vertebrate mammals in these environments. And it doesn't exist. Yeah, at the moment, there's not a lot of good research. It's not a lot of good money. We talked about how, you know, hips lose bone density. I wouldn't want to be the first woman on Mars hoping my hips are going to hold out when labor kicks in. Oh, gosh.

There's just a lot of other things to work, like rat moms who have been sent to space during part of their pregnancy. When they come down, there were kinds of labor contractions that they had to do twice as often, as if any woman would want to be in labor any longer. than they already have to be. It's just lots of reasons to be scared that the space environment will be bad. Could I add one thing to that real quick? Yeah.

That we should have put a pin in earlier, which is most of the people have ever been to space are middle-aged men overwhelmingly. So when we say we know X, Y, and Z about bodies in space, we are mostly talking about middle-aged men from the U.S. and Russia. Like, we don't know much about kids, right? Certainly we know nothing about babies or teenagers,

but even like the data on women is quite limited. Women were not allowed into the U.S. program until 1978. Russia technically flew women earlier twice. To this day, it's something like 10% of all people who've been to space are women. So, you know, we can say we have this kind of data on bodies, but most of the bodies are bodies like mine, middle-aged men, except their bodies are a little more fit maybe. But so, like, there's very basic data we're still missing.

And, like, speaking of, like, very basic data missing, we haven't even talked about the issues with like child development. Like you were saying that there's this bone loss in space and is that going to be a huge concern with babies? So I'm a little concerned about bones and babies because if you're living underground, you're not getting sunlight. Sunlight is important for producing vitamin D and vitamin D is important for making calcium and putting that into your bones.

So if you've got like women who are living underground and you're not taking care to make sure they're getting enough vitamin D and they're turning that into calcium, while they're trying to maintain their skeleton, which is, degrading under less than Earth's gravity and trying to make the skeleton of a baby. And so you can imagine that babies would be born with skeletons that are already a little bit more fragile, a little bit less tough than we would like them to be. And then we don't understand what development under 40% of Earth's gravity is going to do to those bodies. And in particular, we don't know if they'll ever be able to return to Earth if they decide that they don't want to stay at Mars.

So you might be having babies that are forced to stay in this environment that is hostile. And at some point, we might decide we want to abandon, but they wouldn't be. able to. How has working on this book changed your attitude towards Earth? If it has. So I'm an ecologist by training, and in particular, I'm a parasitologist, so I study parasites. So I'm the kind of person who is even in love with the weird, creepy things you find inside of the more charismatic megafauna. So I was already pretty crazy about this planet and all the cool biodiversity we have here. Me too. But reading about, like, if you go to Mars, you'll never be able to walk outside without a space suit on and, like, feel the breeze on your skin.

I just, I really appreciate this planet that we evolved on and we're so well adapted to. I'm staying here. You know, the way we like to say this is that there is no plan B. Elon Musk might want to put on a cowboy hat and fly off to Mars and start his Martian city and leave this polluted planet behind to its wars and devastation. and if he thinks that he is a fool because Mars is so bad you could not, for $10 trillion, make Earth as bad as Mars.

You could zap us with asteroids and unleash every disease you can imagine and start a couple nuclear wars. It's still not even close. That's how desolated everywhere else in the solar system is. So we have to make it work here. It doesn't matter if you love it or hate it. This is the only option,

and it will be that way for a very long time. Kelly, Zach, thank you so much for talking with me about if we could live on Mars. Thank you for having us. Yeah, thanks for having us. This is wonderful. This episode was produced by Jessica Young. It was edited by our showrunner Rebecca Ramirez, and the facts were checked by Tyler Jones.

The audio engineer was Gilly Moon. Betzanovin is our senior director, and Colin Campbell is our senior vice president of podcasting strategy. I'm Regina Barber. Thank you for listening to Shortwave from NPR.