Planetary Radio • Nov 08, 2023

A City on Mars

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Kelly weinersmith portrait

Kelly Weinersmith

Adjunct with Rice University in the BioSciences Department

Zach weinersmith portrait

Zach Weinersmith

Comic artist for Saturday Morning Breakfast Cereal

Bruce betts portrait hq library

Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

Sarah al ahmed headshot

Sarah Al-Ahmed

Planetary Radio Host and Producer for The Planetary Society

Can we build permanent human settlements in space? It might be more complex than you think. Kelly and Zach Weinersmith join Planetary Radio this week to discuss their new book, "A City on Mars: Can We Settle Space, Should We Settle Space, and Have We Really Thought This Through?" Then Bruce Betts, the chief scientist of The Planetary Society, and host Sarah Al-Ahmed chat about some of the most significant challenges humanity might face as we build habitats beyond Earth.

A City on Mars book cover
A City on Mars book cover “A City on Mars: A City on Mars: Can We Settle Space, Should We Settle Space, and Have We Really Thought This Through?” by Zach and Kelly Weinersmith was published on Nov. 7, 2023.Image: Kelly and Zach Weinersmith / Penguin Random House
SpaceX Mars settlement concept
SpaceX Mars settlement concept SpaceX hopes to create the first Martian settlements using their BFR reusable rocketship. This artist’s concept shows a future settlement on the red planet.Image: SpaceX


Sarah Al-Ahmed: Can we settle space? It might be more complex than you think, this week on Planetary Radio. I'm Sarah Al-Ahmed of The Planetary Society, with more of the human adventure across our Solar System and beyond. Kelly and Zach Weinersmith join us this week to discuss their new book, A City on Mars. Then Bruce Betts, the chief scientist of The Planetary Society, and I will talk about the most significant challenges humanity might face when we build habitats in space. If you love Planetary Radio and want to stay informed about the latest space discoveries, make sure you hit that subscribe button on your favorite podcasting platform. By subscribing, you'll never miss an episode filled with new and awe-inspiring ways to know the cosmos and your place within it. As space fans, many of us dream about a future where humans live all across the worlds of our Solar System. Imagine living on the Moon, calling up your friend on Mars, and then taking a vacation together on a spinning space station in orbit around Saturn. Humanity has made a lot of progress toward this goal and there's so much to be hopeful for, but the task is much more complicated than people think. As governments and commercial space companies race to meet the challenge, it's a good moment to take a step back and really make sure that we're thinking it through. Our guests this week, Zach and Kelly Weinersmith, were so excited about the prospect that they decided to write a book on this subject. Of course, the more they learned, the more they realized that it's not as simple as we all hoped it could be. Classic. Kelly and Zach Weinersmith are a wife and husband research team that spent four years trying to understand what it would take for humans to settle space. Kelly is a biologist and Zach is a cartoonist. You may have seen his work on Saturday Morning Breakfast Cereal. With the powers of science, historical context and humor, they went on a mission to understand this complex topic, attending conferences, conducting interviews, and reading books and papers to produce what I think is one of the most well-rounded analyses of human habitation of space that I've read in a long while. Their new book called A City on Mars: Can we Settle Space, Should We Settle Space, And Have We Really Thought This Through was released on November 7th, 2023. Hey, Zach and Kelly. Thanks for joining me.

Kelly Weinersmith: Thanks for having us.

Zach Weinersmith: Just happy to be here.

Kelly Weinersmith: Yeah, we're thrilled.

Sarah Al-Ahmed: And I understand you are both Planetary Society members. That's really cool to have you come on the show. And I got to tell you, reading this book was very vindicating for me. I feel like as space fans who really want humanity to get this right and to hopefully someday be Star Trekking across the universe, it's really easy to get carried away with yourself. But we really need to do this mindfully, and I feel like that's what this book is all about.

Kelly Weinersmith: Thanks. We didn't know how careful you'd have to be when we started writing the book. But we are, yes, now very much convinced it needs to be done carefully. But we hope to get to Star Trekking across the universe.

Zach Weinersmith: Yeah.

Sarah Al-Ahmed: Is that why you felt so compelled to write this book?

Kelly Weinersmith: So, we felt compelled to write the book because we had written a book about emerging technologies and with the drastically dropping cost of SpaceX's rocket launches, we thought, "Oh man, the thing that's holding space settlements back is that you need all this equipment to keep humans alive, and now we can afford to send it. And all these asteroid mining companies, they're going to make it so that we can build habitats out of the asteroids. And so this might happen in our lifetimes, and we're sci-fi geeks, so let's write the book about what's coming in the next few decades." And that's what we told our editor we were going to write. But that's not the book we ended up writing because we ended up thinking it's not that close, actually.

Sarah Al-Ahmed: That's so funny because as with any good science thing, the more you learn about it, the more that you dive down that rabbit hole, the more complex it gets.

Kelly Weinersmith: Yeah.

Zach Weinersmith: Yeah.

Sarah Al-Ahmed: And I loved the dedication that you put on the front end, because clearly you had to talk to a lot of people in order to write this book, really dive into their research. But I wanted to read this just to give everyone a little bit of context for what this book does. The dedication reads, "To the space settlement community, you welcomed us and you shared your wisdom, also your data. We worry that many of you will be disappointed by some of our conclusions. But where we have diverged from your views, we haven't diverged from your vision of a glorious human future." I love that. And that's a beautiful apology. Why did you think it was necessary to include that?

Zach Weinersmith: To be honest, in addition to whatever we felt was necessary, we're very anxious people. If you come out with a book about how something awesome is going to happen tomorrow, whether people believe you or not, they'd enjoy the enthusiasm and you get together and it's fun and everybody's having a beer and congratulating each other. And we ended up just feeling like we couldn't write that book based on what we had found out in our research. And we felt very anxious about that because these people become our friends. They are still our friends. I don't want to act like we've...

Kelly Weinersmith: Yeah, they're still our friends.

Zach Weinersmith: To our knowledge, we have not been disowned by anyone. But we ended up having to say, "Upon research, it appears much more difficult and in some ways questionable."

Kelly Weinersmith: All these people who I asked for interviews when I was like, "Yay, space settlements," they're going to think that I was lying to them when the book was, "Nay, space settlements." And so, we just wanted to apologize. And thank goodness for our editor who eventually was like, "Look, you clearly have changed your mind about space settlements. You need to write the book about why space settlements are not good." So yes, we're sorry.

Sarah Al-Ahmed: But sometimes you come across a conclusion that's inevitable. It's not that we're never going to go to space, but that if we do it the wrong way, we might cause some serious pandemonium.

Kelly Weinersmith: When I talk to my daughter I say we're the space wet blankets. And so anyway, we do-

Zach Weinersmith: She's nine. She's nine.

Kelly Weinersmith: She's nine. Yeah, yeah, yeah. Right, right. Yeah, so when we go to parties, we're like... Everyone's, "Oh, space settlement. You're writing about how we're going to live in those glass domes on the Moon." And we're like, "No, you'd be fried by radiation." And they're like, "Oh, go home." Why [inaudible 00:06:07].

Zach Weinersmith: Yeah, yeah, right.

Sarah Al-Ahmed: Well, happily, this book does a really cute thing and that in between all of these deep thoughtful bits of expounding on these complex ideas, it includes all these cute little drawings and cartoons along the way. And I understand you did that because you, Zach, are a cartoonist.

Zach Weinersmith: Mm-hmm.

Sarah Al-Ahmed: How did you make the decision to do that? Did you do that in your previous book or did you feel like you needed to do it with this one in order to add some levity?

Zach Weinersmith: It was a couple of things. Yeah, so the previous book did have... We actually requested for this book that we would keep the illustrations because it's like a tone we do. But the ones in this book, there are a few ones that are just jokes, but mostly they're illustrations with a joke that are trying to explain something. One, I think the audience recognizes a certain style that we do, so we wanted to preserve some of that. But also when you're trying to do pop science, there are basically two approaches you can take. You can either simplify a lot so the audience doesn't get bored when you're getting into the details, or you can get into the details but try to lard it with jokes and drawings and stuff that'll keep the audience going. Because there is some stuff that's tough to understand but is really, really, really important. And so we would rather keep it coming thick and just try to get the audience through it than try to make it too easy and lose some of the important nuance.

Kelly Weinersmith: Yeah, so we've got four or five chapters on international law that we think are absolutely critical for understanding how going to space could go poorly and how you might be able to structure it so that peace is preserved. And so we told our editor, we're like, "We're thinking four to five chapters on international law." And she was like, "Oh, you guys better make that funny." So, we did a lot of outside reading. So, in addition to Zach's great artwork, we try to include as many funny stories as we can by reading broadly about what's happening in that time period to try to lighten it up. So, at the end, we hope people really understand the international law situation regarding Global Commonses.

Zach Weinersmith: But there is a section on whether space cannibalism is legal, which will help motivate you.

Kelly Weinersmith: To get there. Yeah, that's right. There was a big debate about putting that in the book or not, but in stayed.

Sarah Al-Ahmed: Well, that's it. There's so many of these nitty-gritty complex things that people don't really think through when they're thinking of going to space. What do you do with an entire colony's poop while they're up there? These are really important details, but you have to get far enough into the process of figuring out how to put people somewhere before you even begin to think about these ones, which is just good to think about it now.

Kelly Weinersmith: Yeah, and that's why we think that the timelines that, for example, Musk puts forward are really unreasonable. So he wants boots on Mars by 2029 or something, and a million people by two or three decades after that. And the biggest closed loop experiment that has happened so far was Biosphere 2 in the '90s where there were eight people in a 3.14 acre facility, and we couldn't even get that to work. And that's substantially larger than anything we could build on Mars. There are definitely lots of smaller experiments, but they often have things break and if something breaks on Mars and you didn't bring enough equipment, it's not, "Oh, that's a bummer," it's, "Oh, everybody's dead," which could be bad for future missions to space if inspiration is part of the goal.

Sarah Al-Ahmed: We're just going to have to figure out what redundancies we need and at what level in order to sustain that many people, because woe unto you if your toilet breaks on the way to Mars.

Kelly Weinersmith: Yes. No-

Zach Weinersmith: Yeah.

Kelly Weinersmith: And, man, we read a lot about toilets in space. Every astronaut tells you about their experience with the space toilet, and apparently it's what they're asked the most.

Zach Weinersmith: The toilet section in our book is drastically cut down from a much more ambitious toilet section.

Sarah Al-Ahmed: You need to put that in the addendums or something. I would read it.

Zach Weinersmith: See appendix B for...

Kelly Weinersmith: ... for 50 more pages on the toilets.

Sarah Al-Ahmed: I think something that I hadn't really grappled with in my own heart was the motivations that we're using to justify going to space with humans. There are so many ways that we tell ourselves that this is a great idea, it'll inspire the future. Maybe there's a planetary defense reason. We don't want to keep all the humans on Earth just in case we get hit by an asteroid. Maybe there's monetary gain. But as I was reading this, I began to understand that maybe a lot of my thinking around this was not very deep. I hadn't even really considered that maybe asteroid mining won't be lucrative, maybe sending people to space could actually cause space wars and we'll get ourselves in some serious trouble. So just even analyzing that by itself, why should we go to space, do you think there is a compelling reason for why we should attempt this?

Zach Weinersmith: Yeah, so we spend a lot of an opening section discussing reasons we think are not plausible, but we argue there are at least two arguments that are potentially not bad for going in space. And we call this the hot tub in the cathedral spectrum. So a hot tub argument is just a stupid joke, but the idea was essentially... And a lot of space fans will say this, they'll say, "Well, you authors, or international scholars, or whoever, can say we shouldn't do it or that there's no good reason to do it, or whatever you want to say. But that's true of most things humans do." So when you go to buy a hot tub, there's not a third party that says, "Is this really advisable?" You want to buy it and there's someone selling it and you're good. It's just a regular sort of transaction. And so that would be in contrast to something like nuclear weapons where we say, "Actually third parties do get a say." I actually looked up, even if you look at the most libertarian people, they usually are not cool with private transactions for nuclear weapons. So then the question is, a lot of the aspects of space potentially create dangers for Earth, and then the question is then how much does a third party get to wag its finger? But the basic argument is at least plausible. We don't need an argument if Mr. Musk wants to spend a hundred billion sending some cool stuff to Mars, why does he need anybody's permission? And then the second argument, we basically say there's really no good human existential risk argument in the short term. People say, "We got to get off Earth, because we're going to blow it up somehow or an asteroid's going to come." And basically those arguments aren't good essentially because asteroids like that are extremely rare. Space itself is quite awful, much worse than an Earth hit by an asteroid. And anyway, we can't do it in the allotted amount of time that'll stop climate change or whatever else you're worried about. But, if you see it as a long-term Star Trekkie goal, like in the 2250, it might be a reasonable move to have a multi-planetary humanity for species safety or even just purely aesthetic reasons, then there's work to do and so we should be doing that. That's the second argument. And then a lot of the book is just exploring all the little questions to try to add up to answers to whether those remain good arguments.

Sarah Al-Ahmed: Yeah, my gosh, it's such a giant topic and I love that you've given us the opportunity to actually think through all of these consequences. And let's just actually start chewing through this, because there's so much to consider. Part one of your book is all about caring for the space fairing, caring for people who are actually going to space. Which of these things do you think are going to be the biggest hurdles for us to overcome as far as caring for people in space?

Kelly Weinersmith: So, I think that's a really hard question to answer because we know so little. And this is maybe the thing that surprised me most when we started doing the research. I pulled out the space medicine textbook and I'm like, "All right, we've had over 500, maybe 600 astronauts and cosmonauts in space. We've been running the International Space Station for, what, more than 20 years. We probably know a lot about how the human body responds to space, so we'll summarize all of that." But very few people are proposing that you set up space settlements in low Earth orbit that aren't rotating. And so they're proposing maybe the Moon as a starter spot so we can figure out what we're doing. Mars is probably the most popular option. And then there's the rotating space settlement people. And for all of those locations, you don't learn what you need to know from the International Space Station. So the International Space Station is protected from radiation by Earth's magnetosphere and space has a different kind of radiation than we've got on Earth and we don't understand it very well. And the astronauts are not giving us good data, not just not being exposed to it, but also because only up there for weeks or months or the longest consecutive stay was I think 437 days by Cosmonaut Polyakov. And so we're not getting the kind of data we need on how radiation impacts the human bodies. We are not getting information that we need on how partial gravity impacts the human body. So, yes, if you had to do surgery on the International Space Station, the bowels inside that person would be floating around. You'd have to be working around them. If any blood got out, it would be floating around in the air, forming these little spheres moving through your habitat, that would be tough. But on the Moon or Mars, you have partial gravity. So we don't know yet if that partial gravity is going to be enough for your bones and your muscles to be as strong as they need to be. So on the International Space Station, every month people, in their hips, lose something like 1% of their aerial bone mineral density, and that is a measure for osteoporosis. So astronauts in space over just a month are progressing towards osteoporosis slowly. Now, if you go to Mars and instead of losing 1%, you lose 0.2% per year, so maybe it's way slowed down and under Martian partial gravity, but I still don't want to be the first woman at age 20 who's keeping my fingers crossed that my hips hold up and that was enough when labor kicks in. And so there's a lot that we don't know about how partial gravity is going to impact our body. And again, all the data come from adults. And our book is about space settlements and settlements are all about having babies and being able to have generations. Your plan B society isn't going to be helpful if you can't grow it onsite. And babies become particularly scary because if radiation or development are impacted by space radiation or partial gravity, what is going to happen to the babies? Not to mention the fact that Mars its soil is 1% per chlorate, which is a hormone-

Sarah Al-Ahmed: Right.

Kelly Weinersmith: Yeah, a hormone disrupting chemical that binds to thyroid hormones and messes them up. We need those. We don't know what a growth spurt would be like for a teenager on Mars. But at the end of the day, we felt like we knew so little about how to safely have babies in space, we felt like it essentially is experimentation on humans if you just go to Mars and start having babies, because there's all this stuff we don't know. And the rodent data on the International Space Station, there's some other animal research that's been done, but it's not systematic and it's over short periods of time and it's on different stations, different conditions, and the International Space Station was not sent up to get us the data we need for settlement. That wasn't the goal. And so not surprisingly, we don't have good data on stuff like that.

Sarah Al-Ahmed: Yeah, it's a really complex thing because I don't know how many people know this, but no woman has been beyond low Earth orbit yet.

Kelly Weinersmith: Right.

Sarah Al-Ahmed: So when they did that Artemis 1 launch, part of what was so great about that was that they were for the first time testing radiation and other things on a mannequin that was female presenting. That's where we're at with this level of research. So we still have no idea whether or not you can get pregnant in space, whether or not you could carry that pregnancy to full term, and then what the consequences would be for that little one when they're born. And I just think of the moral quandary of what happens when you have a baby on Mars. What happens when they're stuck on Mars for the rest of their lives, leave aside the fact that maybe they have that growth spurt and they end up eight feet tall or something. There's so much complexity to that, and I am not even sure how we would begin to test that ethically.

Kelly Weinersmith: Yeah, it's definitely scary. So when we were reading some papers to go back to Biosphere for a second, so those closed loop ecosystems, they require tons of time. I think they spent something like eight hours a day, seven days a week just on subsistence farming. And that's probably what early settlements would be like, just a lot of time maintaining the toilets, growing your plants. And just until things get big enough and you can have the people who have specialties, a lot of your time is going to be spent on fixing these things and it's going to be a dangerous environment. And so we came across some papers that were saying early settlements will not be able to handle having people around who can't pull their weight. And so we are going to maybe have to change our threshold for valuable life and maybe if we discover that someone's going to have a child with a disability, we're going to have more liberal abortion policies, which to me read as we're going to say, "I'm sorry you can't have this baby." And to us it was like, "Well then why would we do this now?" If you talk about space as a important because you need to plan B civilization, do you really want to set up a plan B civilization under conditions where you think they're going to have different values for human life and they're going to think that people with disabilities are not worth having around? And what happens when an adult falls or something and becomes quadriplegic? And then of course there's a lot of disabilities that you don't know about until your child is maybe three years old or something. Are we going to be kicking toddlers out of the airlocks? What are the implications here? And so we ended up feeling like we need a lot more research and then we should wait until you can go big and have a big enough facility and a big enough community where if you have people who, for whatever reason, it turns out they can't contribute either for a short period of time or maybe for their whole lives, you are still in a position to value their life and to want to work together and to keep them around. And so that's one of our big arguments for why we should wait till we know a lot more and then go big all at once, so that we can take care of some of these ethical quandaries.

Sarah Al-Ahmed: Yeah, it's funny because I feel like space has the opportunity to allow people who are hurt here on Earth to maybe escape some of that pain. Imagine a world where if you can't use your legs, you get to go live on the space station where gravity is no longer a burden to you. We want space to be something that sets us free and makes us better and kinder to each other and not a space where democracy goes right out the airlock with the person that can no longer work. We are valuable despite our work ethic. So it's... yikes

Kelly Weinersmith: Hundred percent agree. Yeah, and Charles Cockell is well known for talking about how the environment of space is not really conducive to liberty to begin with. So you've got this habitat where oxygen needs to be rationed and someone gets to decide how the resources get used. We're not so great at sharing resources equitably on Earth, and that's when we all are getting all the oxygen and the water that we need very easily. At least in the US, where my husband and I live, it's easy to get oxygen and water. But when you also have that sort of stuff controlled by whoever it is who's managing your habitat, that gets scary also.

Sarah Al-Ahmed: We'll be right back with the rest of my interview with Zach and Kelly Weinersmith after the short break.

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Sarah Al-Ahmed: It looks like at least if we're going to go to space, we have these three major options. Do you think we're going to end up colonizing all of those? And then particularly for Mars, I mean other than perchlorates, what do you think will be the biggest at least physical impediment to keeping those settlements running?

Zach Weinersmith: Yeah, so one way to say it is the Solar System is big, but the actual places you could go to live plausibly are quite small. You really only have three options. You have the Moon, you have Mars, and some people have proposed built stations in space. The problem though, the Moon cannot sustain life without a lot of amelioration. One of the most mind-blowing facts that we came across was that the Moon is low in carbon, which I think your audience is nerdy enough to know what that means, which is we here talking are each about 20% carbon. You cannot get more carbon without bringing it. It has to be made in stars. We joke, it's not like you have to modify the soil a little, you have to literally bring the soil. You have to literally bring the farm to the Moon. So the Moon, as a long-term place for humans to be permanent, to survive loss of contact with Earth, is not plausible. And then we essentially argue that rotating space stations aren't really serious either because in order to make them work, you have to have the kind of infrastructure you would need to build a space settlement somewhere better. And also, their just very, very basic foundational problem, the smallest, plausible, rotating space station is far bigger than the International Space Station. And we joke about... there are a couple of papers written on this very basic idea, which is that if the rotating space station gets unbalanced, you get that same... If you've ever used a centrifuge or your washing machine got unbalanced, it's not good. And it would be really not good if humans were in a survival bubble in your centrifuge. So that leaves Mars. And I can say all the downsides of Mars like the soil and the dust storms that claim the whole planet for weeks at a time, and the fact that it's probably six months inbound and outbound, and that even then you have to stay for a while until Earth and Mars are close to each other, or on a good trajectory. But here's the good thing about Mars. Mars has the buffet of elements we need on Earth to survive, and it also has an atmosphere made of carbon dioxide. It's very thin. Generally speaking, you don't want to breathe pure carbon dioxide, but it is made of carbon and oxygen, which are valuable for all sorts of applications. They're also what plants need to breathe. So, with all of its problems, and the great distance it takes to get there, including the fact that the large distance it takes 22 minutes just to send a message, Mars is really the only place you could seriously consider putting that plan B for humanity.

Kelly Weinersmith: And water.

Sarah Al-Ahmed: But then how do you keep them all... And the water. I mean, you could get water from the Moon from the permanently shadowed craters from the poles, but that's still way less accessible than it is on Mars.

Kelly Weinersmith: And there's not that much of it, which is what always blows our mind when we hear that people are thinking about gas stations on the Moon for rockets. There is not that much of it. If you want to have a settlement there, you probably don't want to burn it into the vacuum of space where you'll never get it back. So, yes, you could get some from the Moon. There's not that much. Mars has lots on the poles, and even on the equator. If you dig down, you're going to find some. So water is much more plentiful and easier to acquire on Mars.

Sarah Al-Ahmed: Mars' probably the place, even if I want to hang out on the Moon. Imagine you build your settlement on the Moon and then 20 years in you've hit peak water and now you're in trouble because you have a whole settlement there.

Zach Weinersmith: Totally.

Kelly Weinersmith: Yeah, that would be disappointing. We do note that one plausible argument for rotating space stations is that if it turns out that that partial gravity thing is a problem and that, for example, women can't go through labor with weakened hips, rotating space stations can be spun up to be whatever gravity you want. And so we could figure out what is the minimum gravity required to make all of this stuff okay, and you could live on rotating space stations, or live your reproductive years on rotating space stations. But that comes up with some weird social problems. But anyway, in general, we think rotating space stations are a difficult sell unless it turns out that this partial gravity thing makes Mars just totally off the table.

Sarah Al-Ahmed: Yeah, we're going to have to do some serious research just to even know whether or not that is something that we require. I'm guessing probably, based on the bone density loss of people just in low Earth orbit. But we're just beginning with this kind of thing, so it does scare me the idea of trying to rush there.

Kelly Weinersmith: Yeah. Yeah, no, us as well.

Sarah Al-Ahmed: And of course, I mean, there's so much to get into about the workings of a human terrarium and how you can even make that work. But I think for me, the thing that I feel is most complex that might take the longest for us to figure out how to deal with, is the space law behind it. All of these scientific challenges, I think with enough time and enough thought we can tackle them. But the complexity of how to get all of the nations around the world and commercial entities to buy in on some kind of space agreement is really hard. Right now, we've got our space treaty from 1967, but as you point out in the book, that was great for 60 years ago. It doesn't cover what we're dealing with today. How do we even begin to tackle this problem of how law will work in space?

Kelly Weinersmith: Well, it's really complicated. And I agree, it's going to be tough to get everybody on board. There's a couple places that you can look for inspiration. So outer space, Antarctica and the deep seabed, these are all places that have been designated as global commons. And they were designated as Global Commons around the same time and around the time that technology started to make them accessible. And so right now, according to the Outer Space Treaty, you can go out into space but you are not allowed to claim sovereignty over anything in space. So you can't land on the Moon's poles next to that water and say, "This belongs to the United States." But there is ambiguity about whether or not you're allowed to say, "Hey, we know this land doesn't belong to us, but we're going to go ahead and extract the water and sell it as rocket fuel and resource extraction. We think that's different and we think that's okay." And right now, the Artemis Accords backs that up, and the Obama administration backed up that interpretation of the Outer Space Treaty. Trump put out an executive order backing that interpretation of the Outer Space Treaty. This is maybe the only thing our political parties can agree on. And the Artemis Accords states that two and a bunch of countries, maybe something like 20 now, have signed on to the Artemis Accords to agree with that interpretation. And so that seems to be the interpretation that's gaining traction. China and Russia haven't signed on, partly because they can't for a variety of geopolitical reasons. But there's still this ambiguity about what's going to happen when we get out into space and what are we allowed to do with the resources. In Antarctica, there is this system where they've decided to prioritize peace over concerns about a scramble for land and a scramble for resources. And so you are not allowed in Antarctica to even look for where the valuable minerals are. You cannot extract them. You cannot try to figure out where they are. There is a moratorium on resource extraction that lasts until, I think, 2048. And even then it can only be overturned by all of the countries that are signed on to the ATS, Antarctic Treaty System. They all have to agree to overturn it, and that's probably not going to happen. And the reason that that was set up that way is because people were concerned about what it would do to the Antarctic environment and what it might do for conflict between nuclear wielding powers on Earth. So they decided peace is more important than resources. For the deep seabed, the United Nations came up with the convention on the Law of the Sea, and after a bunch of different iterations and amendments, it's now widely ratified and signed. And the deal for that area is there's an International Seabed Authority that can figure out who can extract what. So for example, there are these polymetallic nodules down there and they have metals that are useful in things like creating batteries for electric cars, so there's a lot of desire to extract those amongst certain groups. And so the International Seabed Authority right now is figuring out the rules for when is a company allowed to extract and what do they have to do to try to make sure that everybody benefits. And so I think one proposal that was floated for a while was that a company could say, "This stretch of land, we would like to do some resource extraction and then we'd like to sell it, and then half of it gets put aside for developing countries that can work with the International Seabed Authority to extract resources in that other half." And I think that that did not end up being the final rule, but the point is they're trying to figure out the rules right now. And this was another system where they said, "Okay, instead of trying to maximize profits, we're going to try to make sure that everybody gets some benefit. We're going to try and do this peacefully. It's going to be slow and bureaucratic and no doubt about it, there could be better ways to make money than the way its being managed right now." On the other hand, nuclear-wielding powers aren't fighting over these resources. And so we could decide that space was going to be like Antarctica where resource extraction's not allowed, or that space should have an international space authority that decides how... And, I mean, that sounds awesome, so we probably should do that.

Sarah Al-Ahmed: We should probably do that.

Kelly Weinersmith: Immediately. And maybe that organization could decide which resources can be extracted, how they get shared amongst humanity and what the general rules are. So there's other places we can go to get inspiration for how resources can be managed, but at the moment it does seem like different countries are coming up with their best interpretation of the Outer Space Treaty and it doesn't necessarily agree with what other countries, including what other space fairing countries, might be thinking is the right way to go. And we would like to see there not be conflict when different countries go out there and actually are able to start extracting these resources.

Sarah Al-Ahmed: The tough bit there is that in order to incentivize an entire settlement, there's got to be an incentive. And probably that incentive is going to be commercial. I would love a world where we just send pods of scientists to Mars and maybe that's a good functional way to do that. But again, you're probably not going to end up with a settlement of 2 million Mars scientists all living together. So what then would be the incentive? How do you do it without sparking disagreements over territories or resources? I am not sure.

Zach Weinersmith: Yeah, I would add, so we're not convinced that there is right now, or for the near term future, a plausible economic case for anything beyond geosynchronous orbit. Space is obviously quite valuable for remote sensing, navigation, data transmission. Anything past that is pretty implausible. And we go down the line on some of the cases people make, Helium-3 on the Moon, metals on Mars, asteroid mining. And basically the case is not super good. Historically, the reason lots of money has been poured into human space fairing is inevitably and always prestige for nations, and it waxes and wanes with animosity between countries. And so there are, I think, unfortunately a number of space geeks who are salivating for Cold War part two so they can watch the cash floodgates open, which I hope for obvious reasons is undesirable. But also, we argue it might also be scarier at this point because space race part one is to see who can do a cool thing on the Moon first. Space race part two seems to be shaping up around permanent bases, and that's potentially dangerous because the actual good spots on the Moon are extremely limited. As you say, there are places with water. There are very few of them and there's not much water. There are places that get sunlight almost all the time. They're, again, very few. I think we totted up the total area and it's some numbers of hundreds of acres. It's very small. And then when you pair that with the Artemis Accords, which say you can designate a quote, unquote, "safety zone" around your base. It feels turf like. Legally, you can't claim sovereignty. Nobody who goes there is going to say, "We're claiming sovereignty." But there's going to be sovereignty-ish behavior on the Moon, which is frightening.

Kelly Weinersmith: And we should say, we understand why the safety zones were created. You do have to worry if a rocket lands and it blows regolith on a preexisting station. That could be catastrophic for the station that's there, and so you do need to find ways to keep your facility safe. But it does end up essentially feeling like you've walled off this area and other people aren't supposed to come into it, and that starts feeling like sovereignty. And whereas with the Soviet Union, it was a race to get there and then leave, now we're staying. And that seems like it's a much more potential source of conflict, especially if people convince themselves there are resources worth getting there, which to be honest we don't agree with.

Sarah Al-Ahmed: It's a great point too, that the Cold War created this space race, and we like to say that space brings people together, it sparks this international collaboration in space. But as you point out in the book, every once in a while there are these international tensions and then things shift and change. You can see even today how our relationship and space has changed with both China and Russia. So it's aspirational. We want to get to a place where we're actually working together, and it does spark that international collaboration and scenarios where we might not be able to have it other ways. But we could end up with a scenario where it actually creates extra tension, especially if there really are resources that we find, whoever was the first person to get there suddenly has this giant bonus of stuff that they can bring to Earth, and that in and of itself could create tensions.

Zach Weinersmith: Yeah, the one little thing I would add to that is I actually don't even think the resources need to be there. Famously, when Sputnik went up, both Khrushchev and Eisenhower were surprised how much people cared. I think in part because they knew it wasn't significant in a military sense or anything else, it was just like the public at large around the world had a perception of what was there. So we have people in government and industries saying it's really valuable to do stuff on the Moon, and that may be enough. There doesn't actually have to be something worth doing in the financial sense.

Sarah Al-Ahmed: And then we end up with all these space states in space doing their own thing. Hopefully maybe we have some kind of governing authority in space to help us deal with everything. But what happens when one nation or one commercial entity decides to throw someone out an airlock? Who's legally responsible for that? How do you even create a framework to deal with that?

Kelly Weinersmith: It's super complicated. I will say, so according to the Outer Space Treaty, if someone goes to space, they are the responsibility of some government. So if Elon Musk goes to Mars, sets up a Mars settlement and things go catastrophically wrong or he starts breaking international law, it's on the United States to clean that mess up. And often people will push back when we say that and they'll say something to the effect of, "Well, what can you do when Musk is on Mars?" But Musk cannot launch his rockets without FAA approval. I mean, maybe he could launch them in some other country, it would be a thing. But the United States government could say, "We are no longer allowing your rockets to bring resupply to Mars until you start following international law again." So there are ways for nations on Earth to control the behaviors of people in space if they choose to do so.

Zach Weinersmith: So that's where the problem is. It's not in the idea of doing cool stuff in space, we're all for that. It's these geopolitical factors that are dangerous.

Kelly Weinersmith: When we talk to people, we've come across people who will say things like, "Well, SpaceX, they haven't done anything impressive. They got government money." Clearly he has done something that nobody has been able to do before, and the government has had lots of government money and we haven't been able to do it. And so we are impressed with SpaceX. Clearly Musk has done incredible things to drop the cost of rocket launch. What scares us is that he also says things that suggest he's willing to flaunt international law or drop international law, and he seems to be trying to hurry this up at a pace that we think is probably not safe for either the humans who get sent or the humans who are left behind if he sparks geopolitical conflict.

Sarah Al-Ahmed: This is why I'm so glad that there are whole new schools of space law, and a bunch of people just now at this moment in time getting into this field. Because commercial entities sometimes can really speed along the process. It's just there's so much there and we don't have time to get into it, so I'm really glad that people are going to be able to pick up your book, begin reading it, and this next month, if anybody out there is a Planetary Society member, we're going to be reading this book in our book club in our member community app. So we're going to have a fun time kind of chewing through all these hypotheticals together.

Kelly Weinersmith: Yay. Yeah, that's exciting.

Sarah Al-Ahmed: In the end, I don't want to spoiler your conclusions, but in this scenario where we know it is very difficult for humans to build these settlements off of Earth, is there hope? Is there still a reason for us to try to overcome these obstacles?

Kelly Weinersmith: So we end the book by pointing out that, first of all, Zach and I have no power. The most you can say about our clout is that Zach is a good cartoonist and I'm like president of a regional tiny parasitology society. We don't get to say that this can or cannot get done. We can talk about the roadblocks, but we don't get to say no. And in the meantime, there's lots of cool work that can be done when you try to do this safely. We would love to see there be a research station on the Moon where we start getting the data that we need on can generations of rodents safely reproduce on the Moon with no sort of reproductive problems? And you've got scientists who are out there for a decade, do they seem okay? Can they return safely to Earth? And there's tons of really interesting international law stuff that needs to get worked out, tons of research on closed loop ecosystems, which is a fascinating topic. And the better you understand how the various parts of an ecosystem work together, it seems like that could only help our planet at a moment like this where we're worrying about climate change. And so the research between now and when we can safely do space settlements is fascinating and exciting. There's lots of cool stuff to do and maybe settlements won't happen in our lifetime. I think, to be honest, I hope that it doesn't happen in my lifetime because I think racing could have lots of problems, but there's cool work to be done in the meantime.

Zach Weinersmith: And to answer the question of whether there's hope that will do it, I think we basically feel there is, it's just the list of prerequisites is quite extensive. So there is technological stuff having to do with reproduction and ecosystems, which as you said is probably something that can be solved with science. It can't be solved quickly because it involves biology, which is finicky, and it can't be solved by scaling the rockets, although that doesn't hurt. So that needs to be solved. But then the legal stuff is trickier. You really want to be in a world, given how much heavy fast stuff is being put into space or would be put into space under the scenario, given how many different actors would have some level of control over it... You really need a more harmonious Earth to be able to do this safely, unless we get like tractor beams or some crazy Star Trekkie stuff. So that's something worth working towards. And I do think there is some world in which eventually we do have enough advancement and enough of a harmonious Earth that we choose to go to Mars, not because it's going to make us rich, because it probably won't, but because we all want to go and it's just awesome, and it would be sad to just stay here in this one place. But then it's fundamentally an aesthetic choice. It's the thing we do because it's amazing, not because it's going to make us rich or wise or better in any particular way.

Kelly Weinersmith: But that's enough.

Zach Weinersmith: Yeah, that's fine. Let's do it. It's cool. There's cool stuff up there.

Sarah Al-Ahmed: Personally, I think that's the best motivation to do anything, because it's cool, because we can become better along the way. And it's funny, but when I was a kid, my mom always used to tell me that she thought that maybe this venturing into space would be the thing that really forced us to confront these issues. Maybe we have to confront our territorialness and our inability to be kind to one another if we're really going to make this work. Because otherwise, we put ourselves into space and we really magnify what those issues do to us. So I remain hopeful that hopefully we learn some really cool science along the way and maybe we actually begin to think thoughtfully about how to get through these issues together.

Kelly Weinersmith: The wet blankets remain hopeful as well.

Sarah Al-Ahmed: Well, thanks for joining me, Zach and Kelly, and I hope everyone enjoys this book. I'm going to put a link to how they can find it on this page of Planetary Radio. Please join us in our member community for this book club because I think we're going to have a really good time.

Kelly Weinersmith: Thanks so much, Sarah. We had a blast.

Zach Weinersmith: Yeah.

Sarah Al-Ahmed: For being self-identified wet towels about the subject of human space habitation, those two are a lot of fun to talk to. I'll leave a link to the website for their new book, A City on Mars: Can We Settle Space, Should We Settle Space, And Have We Really Thought This Through, on the website for this episode of Planetary Radio at And while you're at it, you can check out their other book, it's called Soonish: Ten Emerging Technologies That'll Improve and/or Ruin Everything. It's definitely on my list. Now, let's check in with Bruce Betts, the Chief Scientist of The Planetary Society, for what's up. What's up, Bruce Betts?

Bruce Betts: The sky.

Sarah Al-Ahmed: Clever.

Bruce Betts: Yeah, I'm clever today. Are you clever today?

Sarah Al-Ahmed: No.

Bruce Betts: All right.

Sarah Al-Ahmed: No, always though, you're always one of the clever people I know, even when you are sleepy, Bruce.

Bruce Betts: Well, thank you, I think.

Sarah Al-Ahmed: We just had a really great conversation about all of the things that could make it really difficult for humans to go and live on Mars. And I'm wondering what you think the biggest challenges are for humanity trying to go to Mars at this point? What are the things that we really, really need to tackle before we try to send humans to the Red Planet for a permanent settlement?

Bruce Betts: Oh, there are so many. The radiation damage to people out there, especially outside the magnetosphere for long periods of time, so there's no protection from the solar wind and cosmic rays. And then that's kind of the duration thing, which you've also just got everything associated with humans in space, bone loss over time, weakness. What do you do when you get there and you've been in zero gravity, assuming you don't rotate the spacecraft or something? How do you suddenly function in 38% gravity? And then there's the trick, which last I knew is pretty well unsolved, which is if you actually plan to go to the surface, how the heck do you do that? And I think we've discussed that here before, but every time they increase the mass a little bit going to the surface, they come up with creative ways to do it and have big challenges. Mars is the worst possible place to land in the Solar System at some level because you have... You don't have no atmosphere, in which case, like the Moon, you can just do retro rockets, and you don't have a thick atmosphere, like Titan or Venus or Earth, where you can use heat shields and parachutes for a very long time. You've got this thin atmosphere, so you can't turn on the retro rockets right away, or you can't float down for a long time. So figuring out how to load... Because they're going to have to land a much more significant mass to keep humans alive on the surface. But you can also go there the first times without going to the surface, that's a possibility and was suggested by a Planetary Society led study a few years ago. But you still have all the problems of humans in long duration flight in space, and there are a lot of them. But, hey, it's a challenge for humanity.

Sarah Al-Ahmed: We could just put each human in their own individual little pod and then just sky crane, parachute everything, wrap them in bubble wrap maybe, and then just have them land that way.

Bruce Betts: Yeah, I'll put you in touch with some of the chief engineers and... No, maybe not. You might want to... That sounds great, Sarah.

Sarah Al-Ahmed: In my heart, I don't really doubt that we're going to figure out how to do it. There are a lot of scientific challenges that we'll definitely face along the way, but I do think that we'll be able to figure those out. What I really question is whether or not we're going to figure out how to treat each other on the way there, whether or not we figure out the space law and the challenges surrounding commercial space and just what happens societally when you send people to Mars? What happens to the kids who might be born there? Are they going to be mad that they were born on Mars and they can't really come to Earth? There's just so much that we'd have to consider there.

Bruce Betts: You're thinking much farther out than I am.

Sarah Al-Ahmed: I know. Well, see, that's it. It's like the human challenges I feel take a lot longer to solve.

Bruce Betts: I mean, not the getting along, that makes sense. I mean, that's a near term, that's one of your problems is your psychology of a crew for that type of duration and that type of isolation. But the other ones I think are a little further out, but I tend to try to focus on the technical because it hurts my brain less.

Sarah Al-Ahmed: The ones that we can actually solve. But thankfully, there are more and more people that are working on space policy and space law, so one of these days maybe we'll have some better idea about how humans will get treated in space so we just don't straight go from zero to The Expanse. Not that I don't love that show or those books, but I wouldn't want to be one of those Belters is all I'm saying.

Bruce Betts: One of those Belters.

Sarah Al-Ahmed: Let's not get into it.

Bruce Betts: Okay. Would you like to hear a...

Speaker 7: ... random space fact.

Sarah Al-Ahmed: I would.

Bruce Betts: Our Solar System orbits the center of the Milky Way galaxy at a relative speed of about 828,000 kilometers per hour, or 515,000 miles per hour. It's about 230 kilometers per second, that's a lot. So at that speed, if somehow you had the speed of the Solar System going around the galaxy, you could go around the Earth in about three minutes.

Sarah Al-Ahmed: I mean, it's funny. I almost want to think that's both faster and shorter than it could have taken. I don't know how to quantify that, so that's a great way to brain that out.

Bruce Betts: It's fast. It's hard to imagine. Yeah, no, I too had weird things. So anyway, and then of course it takes us about a quarter billion years to complete one orbit around the center of the galaxy, with some variability. So we're not very old in terms of our galactic birthday.

Sarah Al-Ahmed: Do you know off the top of your head how do we make that calculation of how fast we're going around our galactic core?

Bruce Betts: I just kind of take an old piece of paper and I write it down and then present it and hope no one asks.

Sarah Al-Ahmed: This is the way.

Bruce Betts: No, I don't. I'm sorry. I could make something up, but it would probably be better to yield to our listeners or looking it up ourselves. I'm not sure how we've done that calculation. I haven't, humanity has done that calculation.

Sarah Al-Ahmed: I do have another question about that though. So we're talking about Earth going around the galactic core in kind of like a circular fashion with all the other things in that disc of the Milky Way, but there's also this kind of up and down, in and out of that disc motion going on.

Bruce Betts: Yeah. Oscillation, yeah.

Sarah Al-Ahmed: That's a totally separate kind of velocity. I would like to look that up sometimes, see how fast we're bobbing in and out of that disc as we're going around the [inaudible 00:51:03].

Bruce Betts: Yeah. Well, I just try to get people to see this rabbit hole to go down and then... Have fun.

Sarah Al-Ahmed: I'm going to be going down that rabbit hole for a long time.

Bruce Betts: This was to tease you and you may prove those exact numbers wrong. And they vary because of stuff like going in that... Anyway, have fun. Have a good time.

Sarah Al-Ahmed: The universe is complicated.

Bruce Betts: It is. And I feel like that's a good point to end on. All right, everybody, go out there, look up the night sky and think about what you would do differently with your life if you could go around the world in three minutes. Thank you. Good night.

Sarah Al-Ahmed: We've reached the end of this week's episode of Planetary Radio, but we'll be back next week to talk about NASA's STEM outreach program. I'm personally really excited to learn more about how kids can get involved in designing a new flagpole for the next time humans go to the Moon. You can help others discover the passion, beauty, and joy of space science and exploration by leaving a review and rating on platforms like Apple Podcasts. Your feedback not only brightens our day, but also helps other curious minds find their place in space through Planetary Radio. You can also send us your space thoughts, questions and poetry at our email at [email protected]. Or if you're a Planetary Society member, leave a comment in the Planetary Radio space in our member community app. Planetary Radio is produced by The Planetary Society in Pasadena, California and is made possible by our members who I really do hope I can someday high-five at Carl Sagan Station on Mars. You can join us as we work together to responsibly and peacefully explore space at Mark Hilverda and Rae Paoletta are our associate producers. Andrew Lucas is our audio editor. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. And until next week, ad astra.