Can we even have babies in space? Why we're not ready for life off-planet

Star Trek makes living in space look great: it depicts a utopian future without hunger or climate devastation and with  technology that can zoom you across the galaxy and produce holographic playgrounds for relaxing in your free time. (Never mind that pesky war with the Klingons.) But the reality of space settlements would likely involve deprivation, harsh conditions and difficult interactions among a small, isolated group of people. Behavioral ecologist Kelly Weinersmith and her cartoonist husband Zach Weinersmith set out to research the future of space settlements and found, to their dismay, that the prospect looked miserable.

Space is inhospitable: its radiation and lack of gravity wreak havoc on the body; the legal situation is murky at best; and there's the looming disaster of trying to reproduce beyond Earth. The Weinersmiths discuss these risks and more in their new book, A City on Mars (Penguin Random House, 2023). Their laugh-out-loud-funny descriptions highlight a sobering truth: humanity isn't ready to spread among the solar system anytime soon.

The Weinersmiths spoke to Scientific American about space war risks, giving birth beyond Earth and the legality of space cannibalism.

[An edited transcript of the conversation follows.]

You started off thinking very differently about living in space than you do now. How did that happen?

Kelly Weinersmith: That's totally right. I'm a sci-fi geek, and I've always thought that living in a space settlement would be really awesome. We thought, this is coming soon, and we're going to write a guide for what it's going to be like as we start making these settlements in the next years or decades. And then, you know, every chapter we researched, we were like, "Oh, crud. We [humans] don't know anything about this." And at the end, we just thought, not only can we not do it safely yet, but it could create a lot more existential risks down here on Earth. And there are also the ethical implications of what essentially sounds to us like experimental research on babies if you just start having kids on Mars. Those all seemed bad.

As you learned more and more about what living in space might involve, you discovered all these new hurdles and potential deal-breakers. What are the biggest things standing in our way?

Zach Weinersmith: One thing is reproduction [in space], about which we know nothing. That's foremost for the simple reason that it's obviously massively unethical not to have that information before you start this. And then there's some stuff that's merely hard and then some stuff that's maybe unsolvable. Ecosystem creation is extremely intricate and complicated. The best example we have is probably Biosphere 2, which had eight people who were starving and angry at each other [after living there for two years in a contained desert ecosystem in Arizona]. So if you want a million-person greenhouse on Mars, it's like a greenhouse the size of Singapore. And so it's a project that's just going to take an enormous amount of time to get answers on, and nobody is spending at scale on it. And then another big issue, I would say, is that you could get a scramble situation for turf in space. You know, conflict happens, and the good turf is actually quite limited. That's a scary possibility. We argue that there needs to be some kind of regulation of how the process works to avoid conflict.

Going back to the question of having babies in space: Are there reasons to think that it's going to be very hard to sustain a pregnancy and give birth in microgravity or on Mars or the moon?

Kelly Weinersmith: Yeah, I think so. The radiation in space, for example, messes up gametes, and for the adults that are walking around, that could give you problems down the line--especially for women, because we're born with our gametes, and so they're going to be acquiring radiation throughout the course of our life. And then we need to have kids, and then those kids need to have kids, and so everything needs to be okay for generations. And we just do not know enough about how space radiation impacts bodies.

And then the other problem is: we don't really know how partial gravity is going to impact human bodies. We know that the microgravity you experience on the International Space Station is definitely associated with bone loss. On a six-month journey, the astronauts that went up there lost 1.5 percent of their bone mineral density per month. If you're living up there--even if you're only losing part of that--by the time you're reproductive age and you're ready to have a kid, you don't want to be crossing your fingers hoping that your hips don't shatter when you go into labor.

You also highlight space law as a problem that gets swept under the rug but really needs to be dealt with. In fact, you say law is a problem "bigger than science or technology" when it comes to settling in space--because essentially it's currently illegal to claim specific territory in space, right?

Zach Weinersmith: This is the big, giant thing nobody's talking about. Space advocates, many of them, just say, "Oh, you know, when we can finally start our settlement on Mars, the international community will just be in awe of our amazingness, and they'll think, 'We couldn't possibly constrain them.'" One famous book about settling Mars, by Robert Zubrin, is The Case for Mars. It's 400 pages long but does not mention the United Nations Outer Space Treaty, which is the main document governing space, at all.

Kelly Weinersmith:A lot of people are hoping that when the time comes, this problem will just go away. Some people think that when the time comes, the U.S. government will be willing to just pull out of this treaty that's been widely ratified for half a century.

Zach Weinersmith: There are also people who think that when there is something valuable to do in space, people--whether it's Elon Musk or the U.S. at large--will just do whatever it takes to go get the stuff because economics trumps geopolitics. I think there's this idea that the moment there's cash money to be made on the moon, none of this [legislation] matters. And we disagree.

A lot of people talk about settling space as a way to make us safer--a plan B in case we accidentally destroy human civilization on Earth. But you write that settling space may actually make us less safe. How does that work?

Zach Weinersmith: If you have a world where there's just more stuff going at higher speed around the solar system, and it's controlled by more players, then you're just in a world of higher danger. [If an object in space hits another] at three kilometers per second, [its] kinetic energy is equivalent to the object being made out of TNT if it impacts , right? And a world with a million tons of metal controlled by private actors in low-Earth orbit is one that imperils Earth below. I don't see how that's avoidable.

In addition, you know, we don't believe there's big value on the moon, but space agencies and governments talk about it. So far there has not been a big scramble on the moon, but now we're getting to a world where that [relative lack of interest] might not be the case. And that's scary because the major players are powerful, highly militarized nations, and they all have nuclear weapons.

And the last thing is that there tends to be this assumption that going multiplanetary necessarily decreases existential risk for humanity. Having two [homes] is better than one. But there are reasons to think that in the longer-term future, if you ever got to a point where you could have war between planets, it could be extraordinarily dangerous. This is because we would be down gravity wells from each other, which not only means that you would get free "boom" from throwing objects but also that you could, in principle, use biological weapons without blowback.

For many people the biggest appeal of living in space is this idea that life will just be better. There will be no sexism or racism; we'll leave behind all the social problems we have here on Earth. And you point out that we're probably going to just take all these problems with us, and they might even be exacerbated. Why do you think people assume that space will be utopian?

Zach Weinersmith: It's kind of like this perfect nowhere, you know, this other place where we can just kind of cut ties. The thing that should make you most suspicious is that different groups have nonoverlapping utopias that they hope will be achieved in space. A very big thread is the libertarian frontier--we're going to go to space and become sort of manly, rugged tough guys, and we'll leave all this wimpy, bureaucratic, socialist stuff behind. But then there are people who are like, we'll have communes in space. A big name in theorizing about rotating space stations was Gerard K. O'Neill, who was famous in the 1970s, and a big sell for him with this project was that you could try out new forms of government in these little island stations, as in, "We can try it all and see who's right." So utopianism has been there since the beginning. It continues now. And there's just not good evidence for it.

Okay, here's a serious question: How did you come to have an actual section of the book dedicated to space cannibalism?

Kelly Weinersmith: [Laughing] Okay, so Zach was like, "Why don't we have a section on the legality of space cannibalism?" And at first, I was like, "No! This is a serious book. We can make some jokes, but we're not going to have a whole section on cannibalism!" And then I read this book by Erik Seedhouse about Mars. And he mentions cannibalism a couple of times. It has this very detailed section about how you can 3-D print implements to cut the people up and who should get cut up first. In the margins of the book, I wrote, "WTF?!" At that point, I thought, okay, I can see where this could go.

Zach Weinersmith: My favorite part of the Seedhouse book was that there was literally a picture of astronauts with the caption "Is it wrong to waste such a neatly packaged meal?" And then we found this paper on survival homicide in the context of space. It was this perfect review paper on whether you can murder someone to survive in space.

Kelly Weinersmith: Then I was like, "Okay, you are cleared to start researching space cannibalism."

Final question: After taking this journey and learning everything that you have, do you ultimately think that we will ever live in space? And do you think we should?

Kelly Weinersmith: I still think it would be really cool if humans lived in space. I still love the idea of people waking up on the moon and maybe opening up their little portal and looking out on Earth and enjoying that view. But I don't think it's going to happen in my lifetime. And I don't want it to happen in my lifetime, because I'd love to see us do the research first to make sure everything is safe--you know, have a research station on the moon for a couple decades where we work out, for instance, "Are rodents okay reproducing in space?" and "Can we make a closed ecosystem where the parts don't break for more than two years, so we know that people on Mars will be okay?" And I'd like us to very slowly figure out rules for how to extract and use resources and who's allowed to go where. All this stuff is going to take a long time. But I don't think humans will ever give up the dream of living in space and being multiplanetary, and I think that's great. I just hope we do it slowly.

Zach Weinersmith: Eventually, hopefully, we will go to Mars en masse just because it's awesome. It's an aesthetic choice we can make when we are an extremely rich and very advanced and very safe civilization. It's like Star Trek; you're exploring because exploring is fun. It's not going to make us rich; it's not going to make us utopian communards or save the environment or any of the other stuff. It's just cool.