Humans on Mars? Here's why you shouldn't plan a space move anytime soon
[MUSIC PLAYING]
REGINA BARBER: You're listening to Short Wave 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.
[AUDIO PLAYBACK]
SPEAKER 1: 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.
SPEAKER 2: I would love to see a trillion humans living in the solar system.
SPEAKER 3: 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.
SPEAKER 1: Some of you will end up working on projects on Mars, and I guarantee that some of your children will end up living there.
ELON MUSK: One path is we stay on Earth forever, and then there will be some eventual extinction event. The alternative is to become a spacefaring civilization and a multiplanet species.
[END PLAYBACK]
BARBER: But I've always wondered, what would a space colony actually look like?
KELLY WEINERSMITH: 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 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.
BARBER: That's Kelly Weinersmith. She's a biologist and science writer, and she and her partner, Zach Weinersmith, 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.
ZACH WEINERSMITH: The Moon, Mars, or creating an orbital space station. And among those, Mars is overwhelmingly the best option.
BARBER: How we might do all the nitty-gritty of daily living.
KELLY WEINERSMITH: 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?
ZACH WEINERSMITH: 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.
BARBER: 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 Short Wave, the science podcast from NPR.
[MUSIC PLAYING]
BARBER: So it feels like people's settlement obsession is mostly focused on Mars. Why is Mars the big candidate?
KELLY WEINERSMITH: 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 the moon, for example, is very poor in 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. OK, let's start with the first hurdle, which is 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 body?
ZACH WEINERSMITH: 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. Studies 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 baroreflex, 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 stress. It 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.
BARBER: Right. But this is a different acceleration due to gravity in orbit versus on Mars.
ZACH WEINERSMITH: 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 zero gravity, you try to imagine, like, kids not developing bones normally. Maybe 40% gravity is enough to make the body work out, or there's even some world in which you wear, like, a weighted suit--
BARBER: Yeah.
ZACH WEINERSMITH: --and that's enough to handle it. But we don't know is the problem.
BARBER: 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?
KELLY WEINERSMITH: 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 planetwide 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.
[LAUGHTER]
BARBER: OK, another question beyond the mole 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?
KELLY WEINERSMITH: 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 regolith, so like the dirt on the surface, has perchlorates in it. These are endocrine-disrupting hormones which mess with metabolism in 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.
BARBER: Oh my God, I hadn't even thought of that.
KELLY WEINERSMITH: 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.
BARBER: Oh yeah, easy.
[LAUGHTER]
KELLY WEINERSMITH: I've got to admit, it's not for me.
BARBER: Let's talk about babies because you 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.
ZACH WEINERSMITH: Yeah. Often when this question 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, right? And there's a bunch of subtle stuff that we haven't gotten 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 generational study on vertebrate mammals in these environments, and it doesn't exist.
KELLY WEINERSMITH: Yeah. At the moment, there's not a lot of good research. There's not a lot of good money. We talked about how 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.
BARBER: Oh, gosh.
KELLY WEINERSMITH: There's just a lot of other things too. 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.
BARBER: Yeah.
KELLY WEINERSMITH: It's just lots of reasons to be scared that the space environment will be bad.
ZACH WEINERSMITH: Could I add one thing to that real quick--
BARBER: Yeah.
ZACH WEINERSMITH: --that we should have put a pin in earlier, which is most of the people who 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 US and Russia.
BARBER: Like, we don't know much about kids, right?
ZACH WEINERSMITH: Certainly we know nothing about babies or teenagers, but even, like, the data on women is quite limited. Women were not allowed into the US program until 1978. Russia technically flew women earlier twice. To this day, it's something like 10% of all people who have been to space are women. So 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.
[LAUGHTER]
ZACH WEINERSMITH: So, like, there's very basic data we're still missing.
BARBER: 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?
KELLY WEINERSMITH: 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.
BARBER: How has working on this book changed your attitude towards Earth, if it has?
KELLY WEINERSMITH: 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.
BARBER: Me too.
KELLY WEINERSMITH: But reading about, like, if you go to Mars, you'll never be able to walk outside without a spacesuit 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.
ZACH WEINERSMITH: 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.
BARBER: Kelly, Zach, thank you so much for talking with me about if we could live on Mars.
KELLY WEINERSMITH: Thank you for having us.
ZACH WEINERSMITH: Yeah, thanks for having us. This was wonderful.
[MUSIC PLAYING]
BARBER: This episode was produced by Jessica Yung. It was edited by our showrunner Rebecca Ramirez, and the facts were checked by Tyler Jones. The audio engineer was Gilly Moon. Beth Donovan is our senior director, and Collin Campbell is our senior vice president of podcasting strategy. I'm Regina Barber. Thank you for listening to Short Wave from NPR.
[MUSIC PLAYING]
Copyright © 2024 NPR. All rights reserved. Visit our website terms of use and permissions pages at www.npr.org for further information.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.