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A City on Mars

Can we settle space, should we settle space, and have we really thought this through?

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Best Seller
* THE INSTANT NEW YORK TIMES BESTSELLER * Scientific American’s #1 Book for 2023 * A New York Times Book Review Editors' Choice * A Times Best Science and Environment Book of 2023 * A Tor.com Best Book of 2023 *

“Exceptional. . . Forceful, engaging and funny . . . This book will make you happy to live on this planet — a good thing, because you’re not leaving anytime soon.” —New York Times Book Review

From the bestselling authors of Soonish, a brilliant and hilarious off-world investigation into space settlement


Earth is not well. The promise of starting life anew somewhere far, far away—no climate change, no war, no Twitter—beckons, and settling the stars finally seems within our grasp. Or is it? Critically acclaimed, bestselling authors Kelly and Zach Weinersmith set out to write the essential guide to a glorious future of space settlements, but after years of research, they aren’t so sure it’s a good idea. Space technologies and space business are progressing fast, but we lack the knowledge needed to have space kids, build space farms, and create space nations in a way that doesn’t spark conflict back home. In a world hurtling toward human expansion into space, A City on Mars investigates whether the dream of new worlds won’t create nightmares, both for settlers and the people they leave behind. In the process, the Weinersmiths answer every question about space you’ve ever wondered about, and many you’ve never considered:

Can you make babies in space? Should corporations govern space settlements? What about space war? Are we headed for a housing crisis on the Moon’s Peaks of Eternal Light—and what happens if you’re left in the Craters of Eternal Darkness? Why do astronauts love taco sauce? Speaking of meals, what’s the legal status of space cannibalism?

With deep expertise, a winning sense of humor, and art from the beloved creator of Saturday Morning Breakfast Cereal, the Weinersmiths investigate perhaps the biggest questions humanity will ever ask itself—whether and how to become multiplanetary.

Get in, we’re going to Mars.
© Zach Weinersmith
Dr. Kelly Weinersmith received her PhD in Ecology at the University of California Davis, and is an adjunct faculty member in the BioSciences Department at Rice University. Kelly studies parasites that manipulate the behavior of their hosts, and her research has been featured in The Atlantic, National Geographic, BBC World, Science, and Nature. When she isn't studying Nature's creepiest wonders, Kelly is writing books with her husband, Zach Weinersmith (creator of Saturday Morning Breakfast Cereal Comics). Their first book, Soonish: Ten Emerging Technologies That'll Improve and/or Ruin Everything, was a New York Times Bestseller. View titles by Kelly Weinersmith
© Zach Weinersmith
Zach Weinersmith is the cartoonist behind the popular geek webcomic, Saturday Morning Breakfast Cereal. He co-wrote the New York Times bestseller Soonish: Ten Emerging Technologies That'll Improve and/or Ruin Everything and illustrated the New York Times-bestselling Open Borders: The Science and Ethics of Immigration. His work has been featured by The Economist, The Wall Street Journal, Slate, Forbes, Science Friday, Foreign Policy, PBS, Boingboing, the Freakonomics Blog, the RadioLab blog, Entertainment Weekly, Mother Jones, CNN, Discovery Magazine, Nautilus and more. He lives in Virginia with his wife/coauthor and his children/coauthors. View titles by Zach Weinersmith
1.

A Preamble on Space Myths

Idyllic views of the future always seem to come with the hidden assumption that human nature will change. That somehow, the flaws of mankind will just melt away amongst the awesomeness of living among the stars. People will abandon mundane flaws like booze and drugs, and also everyone will be super-efficient like some kind of environmentalist's dream. But that's never been the case as we march forward, so I don't see why it would happen in the future.
Andy Weir, world famous sci-fi author who also writes really insightful commentary in books about booze in space. 


Outlandish ideas about space settlement often function as a justification for the whole project, typically promising vast wealth, an improved humanity, or an escape from Earth-awfulness. Because much of this book hinges on the idea that there is no urgent need to settle space, here we'll try to convince you that most of the pro-settlement arguments are wrong. Some of these arguments may be unfamiliar to you, but all of them have at least some powerful advocates in government, military, or business settings.

Bad Arguments for Space Settlement

Argument 1: Space Will Save Humanity from Near-Term Calamity by Providing a New Home

The idea of a multiplanetary humanity as more resilient to extinction is a common one and is plausible over the very long term. However, over the short term, space settlement won't help with any catastrophe you're imagining right this second. Not global warming, not nuclear war, not overpopulation, probably not even a dinosaur-style asteroid event. Why? In short, because space is so terrible that in order to be a better option than Earth, one calamity won't do. An Earth with climate change and nuclear war and, like, zombies and werewolves is still a way better place than Mars. Staying alive on Earth requires fire and a pointy stick. Staying alive in space will require all sorts of high-tech gadgets we can barely manufacture on Earth. We'll elaborate on all of this over the course of the book, but the basic deal is that no off-world settlement anytime remotely soon will be able to survive the loss of Earth. Getting any kind of large settlement going will be hard enough, but economic independence may require millions of people.

We believe there's a decent case for a Plan B reserve of humanity off-world, but there isn't a good case for trying to do it fast. A commonly made argument for urgency is what's sometimes called the "short-window" argument. The idea is that historically, "golden ages" don't last long, so our current age of space travel might come to an end before we get to Mars. We don't know if that's a good analysis of history, but what we can say is that the current age is simply not golden enough to deliver an independent Mars economy. If you want a Mars that can survive the death of Earth, you'd better make sure Earth doesn't die for a very long time.

Weinersmith Verdict: Nah.

Argument 2: Space Settlement Will Save Earth's Environment by Relocating Industry and Population Off-World

There are various flavors of this argument, many of which are popular with the rotating-space-station settlement community, including Jeff Bezos.

One version of this idea is that the solar system contains more than enough mass to create rotating space stations that can accommodate an almost endless number of humans in space. This is literally possible in the sense that there is lots of stuff in space, and the stuff could be refashioned into space bases, but we need a sense of proportion here. The Earth of 2022 puts on about 80 million people per year. If saving our ecology requires us to reduce Earth's human population, then we need to launch and house 220,000 volunteers per day just to tread water.

A related idea is that space should be zoned for heavy industry, while Earth returns to an unpolluted Edenic state. All the nasty mining and manufacturing can be done elsewhere, with by-products cleanly disposed of into the vast landfill that is the solar system. As Jeff Bezos says, "Earth will be zoned residential and light industrial." Again, this is literally possible, and perhaps as long as you're just thinking in terms of big concepts like pollution and mass it sounds doable. But the details are where the difficulty lives. Consider for example cement. It's a major contributor to global warming, so can we make it in space?

Technically, most of the components of cement by mass exist on the Moon, but they won't be easy to dig up. Construction equipment will need to be built to function in an airless environment at low gravity with equatorial temperature swings from -130°C to 120°C. Little things start to loom in this context. Just getting a lubricant that can handle these temperature shifts without degrading is nearly impossible. The same goes for the machines themselves. At extreme cold some metals can undergo a ductile-to-brittle transition; below a certain temperature, metals behave more like stone. However strong they may be, they can't flex and bend. It's speculated that the Titanic sank because its steel hull experienced a ductile-to-brittle transition before hitting the infamous iceberg. That's a nontrivial problem when you desire to use construction equipment that regularly slams into hard surfaces.

And that's just one detail of one part of the process, never mind replicating all those factories. How soon can we plausibly get all these problems solved and then scaled to the needs of Earth, which currently requires over 3.5 billion metric tons of cement per year? And does it sound economically competitive with Earth-made cement even if we could do it? And, by the way, what are the rules for dropping 3.5 billion tons of rock on Earth annually?

Part of what's supposed to make these ideas work is cheap, plentiful energy thanks to space-based solar power. This is another bad idea. Space-based solar power figures prominently in space-settlement proposals for giant rotating space stations. It's also frequently proposed by governments and private space companies as a way to make money while greening the planet. You may have read an article recently about Chinese universities or the European Space Agency, or some new start-up planning to field this technology in the near future. They probably shouldn't.

It's certainly true that there's a whole Sun's worth of sunlight in space, unobstructed by annoying Earth features like weather and the atmosphere. Exactly how much more energy you might get per panel depends on exactly what assumptions you're prepared to make, but different estimates expect about an order of magnitude improvement. That sounds like a lot until you ask yourself what the cost differential will be between a panel in space and a panel in Australia.

It's conceivable that in a world where solar panels are incredibly expensive and there's an extreme collapse in the cost of launching objects to space, you might want to maximize your energy per panel by putting them above the atmosphere. But panels are cheap, and even if we assume pretty steep drops in the cost of space launch, the numbers don't add up. This becomes especially clear when you start to think about maintenance. Try to imagine acres upon acres of glass panels in space, regularly pelted by intense radiation and bits of space debris while enduring the extreme heat of perpetual sunlight. They'll have to be repaired and cared for either by astronauts or an army of advanced robots. Solar panels in Australia can be cleaned by a teenager with a squeegee.

When dumping solar power back to Earth, you have another problem. Solar panels on the ground can send their power right into the grid or to batteries. Space-based power has to be beamed to huge receivers on Earth, losing energy en route. But it can't be beamed at too high an intensity, lest it endanger birds and planes.

Space solar is valuable if you're already in space, as a way to generate energy without burning fuel. It may also be valuable on Earth in some very narrow cases, such as beaming energy to military bases where fossil fuel delivery would be dangerous. For more practical uses, you're better off with conventional boring renewables. Cover every rooftop with solar panels, followed by the Sahara desert, and then if the planet still needs energy, we can talk about space.

We are skeptical that it will ever be a great financial idea to harvest massive amounts of solar power in space and then use that energy to convert moondust into cement or steel or industrial chemicals. But even if we believe that this'll all happen one day, that one day will not come in time to spare us from any environmental concern of today.

Weinersmith Verdict: Unfortunately, no. 

Argument 3: Space Resources Will Make Us All Rich

It's certainly possible, but right now the economics of it aren't looking great. As we'll explore later, no place in space has something like a giant hunk of pure platinum or gold. What space resources do exist are likely to be very expensive to acquire and will remain so even with big improvements in technology.

Also, there's a real difference between access to commodities and universal wealth. Consider aluminum. Discovered in 1825, early on it was so valuable that only the wealthy could afford it. Victorian-era jewelry sometimes includes aluminum as a precious metal. Today, it's a way to cover lasagna. That's because by the late nineteenth century, industrial processes had made aluminum incredibly cheap, effectively flooding the market with a former luxury good. This is a great development, and of course aluminum has uncountable valuable applications from the kitchen to airplanes. But the fact that most of us can buy large quantities of a once-precious metal doesn't mean we're all millionaires.

In our experience, people tend to assume raw minerals are the major factor in human well-being. Although they're necessary inputs into our economies, according to a recent report by the World Bank, nonrenewable resources, in the sense of valuable stuff found in the ground, make up about 2.5 percent of Earth's wealth. And a lot of that is fossil fuels, which are not available in space. The really valuable thing for economies is humans, and our ideas and technology. You can convince yourself by melting down your phone and assessing the value of the resulting glass, metal, and plastic.

Even if space does produce inexpensive access to all sorts of commodities that make someone rich, there's also no reason to assume anything like an equal distribution of wealth back on Earth. In fact, if you believe there's big money in space, the United States is uniquely poised to go get it, potentially harming the economies of less-developed countries dependent on commodities. Some readers will care about this more than others, but even if you don't think wealth distribution has much moral significance, it may still have geopolitical significance. As we'll see later, under some conditions, changes in the balance of power among nations can make war more likely. If space really does make some country especially rich, the consequences don't have to be uniformly good.

Weinersmith Verdict: It's complicated but no, not really. 

Argument 4: Space Settlement Will End, or at Least Mitigate, War


There are a few versions of this one, but we've found these three pretty common: space settlement will create more territory so we'll fight less about territory; space settlement will make us rich so we won't want to fight anymore; and space settlement will allow unhappy citizens to just leave for other settlements, which will reduce tension here on Earth.

The territory argument is the most silly. Nations don't fight over land, they fight over particular land. You can't solve disputes over Jerusalem or Kashmir or Crimea by promising the parties involved equally large stretches of Antarctica. It'd be like going to a nasty divorce proceeding and trying to solve the custody fight by offering to just grab some other kids. Also, if we're defining land as "built structures humans live in," which is the definition you must use for space habitats, well then, on Earth we are creating land all the time. Individual buildings create far more square footage than any space settlement likely to be built anytime soon. Meanwhile, if you personally just want any sort of land there's plenty. Google it. Small towns all over the developed world are offering free land to people willing to move there instead of big cities.

The argument about riches may sound tempting; if humans are rich, why would we fight? But the "money makes us all friends" argument isn't one that all war scholars buy. Wars start for all sorts of reasons that have nothing to do with a bunch of people looking at their resource base and saying "hey, this is pretty good." A nonexhaustive list of causes of war includes: religious differences, leaders who don't bear the cost of the violence, and misperception about the other party's strengths or intentions. Even if space activity left everyone better off, it wouldn't stop nations from having religious differences, bad leaders, or suspicion about rivals.

As for peace through allowing people to just move between settlements, well, we should consider that most people aren't even allowed to do this between nations on Earth. Space will likely be worse. However you feel about immigrants coming to your country, one thing you probably don't fear is the possibility that they'll breathe too much air. In space, the atmosphere is constructed, as is the ground beneath your feet, and individual settlements will only be rated for certain population sizes. That's not obviously an environment where you'd expect to see open borders. Some advocates note that you can always just create a new place to live in space, but then the argument becomes "you can just pull up stakes by creating a million-ton space station," which, we suspect, will not be a live option for most of us. Even if it were, it's still not clearly desirable. Dr. De Witt Kilgore, one of the few historiographers of ideas about space, called it a form of celestial "white flight." That is, space not as a solution to politics, but as an escape from political realities one group finds uncomfortable.

Weinersmith Verdict: Nope.

Argument 5: Space Exploration Is a Natural Human Urge

This is a popular one. The basic idea is that yeah, maybe there's not a good return-on-investment reason for space exploration, but if we don't do it, we'll be thwarting our own nature, resulting in widespread human stagnation. The prettiest version of this argument is of course from Dr. Carl Sagan: "For all its material advantages, the sedentary life has left us edgy, unfulfilled. Even after 400 generations in villages and cities, we haven't forgotten. The open road still softly calls, like a nearly forgotten song of childhood." It's a nice idea, and much better written than any of our Uranus jokes. Also, it can be hard to argue against views like these because it's not always clear what the exact claim is. However, when people do get specific, they tend to point to two things: famous human explorers, and the fact that humans have spread around the world.
“This playful ‘homesteader’s guide’ to space settlement presents a bleak view of the pursuit . . . The authors examine the increasingly popular dream of a multi-planetary human race with a skepticism informed by ethical, logistical, and legal anxieties.” The New Yorker

“A wonderful example of what it means to really think a difficult project through, a skill that many of us should acquire . . . The Weinersmiths are self-confessed space geeks who tread a fine line between the sort of constructive critique that would still qualify them as bona fide members of the space-settlement movement and a style of gentle ridicule that might get them rejected as traitors to the cause. A City on Mars is, foremost, a case study in the application of common sense.” —Shlomo Angel, Wall Street Journal

“An exceptional new piece of popular science . . . Forceful, engaging and funny… an essential reality check for anyone who has ever looked for home in the night sky . . . hilarious. The breezy prose is studded with charming cartoons . . . This book will make you happy to live on this planet—a good thing, because you’re not leaving anytime soon.” New York Times Book Review

“Engaging . . . breezy . . . honest yet hilarious . . . delightful cartoons sprinkled throughout the book are sure to pull chuckles out of you.” —Space.com

“Laced with humor but with a real gut punch . . . a fascinating book, packed full of racy space stories, that raises serious questions about the future of human space travel and settlement.” The Explorers Journal
 
“Laugh-out-loud-funny.” Scientific American
 
“Excellent . . . sets out persuasively and amusingly why you would have to be wildly optimistic or crushingly stupid to want to set up a space settlement any time soon.” —Stephen Bush, FT

“Mix of expertise and humor . . . In a world hurtling toward human expansion into space, A City on Mars investigates whether the dream of new worlds won’t create nightmares, both for settlers and the people they leave behind.” —Daily Kos

“The Weinersmiths artfully encourage readers to entertain the thought of living on Mars while skillfully highlighting the absurdity of such a prospect through compelling data and delving into serious questions all through a lighthearted lens . . . [this] tongue-in-cheek narrative will captivate even the skeptics, directing their gaze upward at night.” —Debbra Palmer, The New York Journal of Books

“Helpfully pulls back the curtain . . . painstaking research, clear-eyed objectivity, and good-natured humor . . . Any reader enthusiastic about space settlement will find much to appreciate in this book . . . most importantly, they write with a confident belief that humanity will one day travel off-planet.” Gifford J. Wong, Science
 
“A sobering book, but also, ultimately, a hopeful one—and perhaps recommended reading for lots of sci-fi fans out there.” —Charles Bonkowsky, Tor.com (Reviewers’ Choice, Best Books of 2023)

“Hilarious, highly informative and cheeky book . . . use[s] humor and science to douse techno dreams with a dose of reality . . . Even as they shoot down a long list of space fantasies, they explore a lot of really interesting research.” —Christie Aschwanden, Undark

“Entertaining and informative romp through what’s stopping us from moving off-planet . . . Well researched and argued, it’s also a very fun read.” —Jennifer Rothschild, Arlington Magazine

“Full of some of the choice-iest bits of awkward human space exploration histories and theories . . . could have been the research notes for an Ursula K. Le Guin, or a James S. A. Corey story, except that it’s filled with jokes, palette cleansing anecdotes and charming cartoon illustrations . . . a popular science book that reads like a conversation with a friend . . . you can’t get away from this book without thinking about how precious life on Earth is.” —Mark Popinchalk, Astrobites

“Science writing is rarely as readable (or deflating) as A City on Mars, an informed, irreverent study of how little we actually know of the practical considerations of space colonization, from sex and legal cannibalism to issues of settlement.” Chicago Tribune, 75 Top Picks for Fall

“Starting life anew somewhere far, far away sounds appealing. But that fantasy is so much further from realization than we think, argues this wife-and-husband-team persuasively.” MIT Tech Review

“Inventive, funny, and informative . . . Filled with fun illustrations that bring the writing to life, this accessible and thought-provoking book explores what it will really take to build a society on another planet.” American Scientist

“[A] romp through the many rooms of space folly… amusingly literal and impeccably scientific”—Stuart Jeffries, The Guardian, Book of the Day (UK)

“A very funny book, underpinned by deadly serious questions about the future of humanity.” —Ben Spencer, 19 Best Science and Environment Books of 2023, The Times (UK)

“This witty and wildly informative guide to space colonization boldly goes where few books have gone before . . . engaging, wildly informative, insightful, and frequently funny.” —Rhys Blakely, The Sunday Times, Book of the Week (UK)
 
"Rich food for rocketheads and critics alike. Kelly and Zach Weinersmith bring tough love to the idea of Martian settlement in A City on Mars, a sharp, well-informed and very funny book."Simon Ings, The New Scientist, Best Books of 2023 (UK)
 
"Is living off-world not the ultimate insurance policy for our species? A City on Mars... answers this question very bluntly: don't pin your hopes on it ... peppered with cartoons and jokey-back references, and between each section are interludes tackling some enjoyable anecdotes from space"James Ball, The Spectator (UK)
 
"Informative and entertaining"Andrew Crumey, Literary Review (UK)
 
"Manages to be at the same time informative, sceptical and hilarious"Engineering and Technology, Books of the Year

“Wickedly irreverent . . . The cheeky tone is loads of fun, and Zach’s humorous illustrations of, for instance, contraptions proposed to facilitate zero-gravity sex, entertain . . . A boisterous takedown of techno-utopianism.” Publishers Weekly (starred review)

“Immersive and entertaining . . . the Weinersmiths' passion and enthusiasm shine through every page of this absorbing, lively exploration.” Booklist (starred review)

“An entertaining illustrated assessment of space settlement. This book is, to put it simply, a romp . . . A fun, informative read that puts the pop into popular science.” Kirkus

“There is simply no more engrossing, entertaining, or thorough way to understand the intense challenge of humanity's off-Earth future than A City on Mars. I laughed the whole way through.” —Hank Green, New York Times bestselling author of An Absolutely Remarkable Thing and host of CrashCourse and SciShow

“Scientific, educational, and fun as hell.”—Andy Weir, New York Times bestselling author of The Martian and Project Hail Mary 

“Listen up, humans. How to poop in space will be the least of our concerns. Herein are challenges most space-heads, including me, never even considered: not just technological, but legal, ethical, geopolitical.  Despite the breadth and depth of research and some impressive near-wonk-level detail, this is a clear, lively, and hilarious read.  Slam dunk, Weinersmiths!"—Mary Roach, New York Times bestselling author of Fuzz and Packing for Mars

“A must-read!” Jonathan McDowell, Center for Astrophysics, via X

“This might be the best book ever written about humans in space, or at least the funniest. I don't know of anything else quite like it: an extended, comical confrontation between the dreams of space colonies and the gross, dangerous, tedious realities. Read it before you go.” —Scott Aaronson, Schlumberger Chair of Computer Science and Director of Quantum Information Center, University of Texas at Austin

"Of the many books and extensive literature on Space mission architectures, technical and otherwise, this is the only one that is a must-read to understand the deep financial, physiological and technical constraints of one of the largest and most ambitious endeavors of our time: enabling humans to become a multi-planetary species.” —Professor Sinead O'Sullivan, member of the Advisory Council of the European Space Policy Institute

“A fun, and sobering, exploration of what it means to explore beyond our planetary home. Sure, the stars beckon and TV shows and movies make space travel seem like a blast, but before you invest in another billionaire’s crypto-powered Mars colonization dream, you might want to pick up this book and learn about the risks, astronomical costs and thorny ethical issues involved. The Weinersmiths take you on a journey to our unlikely future on other planets with impressive detail, eye-opening facts, and extremely funny cartoons.” —Jorge Cham, author of Oliver’s Great Big Universe and creator of PHD Comics

“Earth may not be perfect, but we evolved here. Everywhere else in the Universe will try heartily to kill you in nasty ways. The Weinersmiths logically and patiently lay out the case that if we want to live in space, there's a lot of ground work to do first. If you're a gung-ho Moon and Mars enthusiast, this book will show you why it's best to slow down the space race just a bit.”—Phil Plait, writer of the “Bad Astronomy Newsletter”

“A City on Mars is deeply researched, hilarious, and sobering. Zach and Kelly Weinersmith have given us a bracing to-do list for the new age of space. Highly, highly recommended.” —James S.A. Corey, author of The Expanse series

“A refreshing, clear-headed breath of life-support oxygen amidst all the tech-bro naivety and hype on space colonisation. Impeccably researched and argued, yet witty and very easy to read. Superb!” —Professor Lewis Dartnell, New York Times bestselling author of Being Human

About

* THE INSTANT NEW YORK TIMES BESTSELLER * Scientific American’s #1 Book for 2023 * A New York Times Book Review Editors' Choice * A Times Best Science and Environment Book of 2023 * A Tor.com Best Book of 2023 *

“Exceptional. . . Forceful, engaging and funny . . . This book will make you happy to live on this planet — a good thing, because you’re not leaving anytime soon.” —New York Times Book Review

From the bestselling authors of Soonish, a brilliant and hilarious off-world investigation into space settlement


Earth is not well. The promise of starting life anew somewhere far, far away—no climate change, no war, no Twitter—beckons, and settling the stars finally seems within our grasp. Or is it? Critically acclaimed, bestselling authors Kelly and Zach Weinersmith set out to write the essential guide to a glorious future of space settlements, but after years of research, they aren’t so sure it’s a good idea. Space technologies and space business are progressing fast, but we lack the knowledge needed to have space kids, build space farms, and create space nations in a way that doesn’t spark conflict back home. In a world hurtling toward human expansion into space, A City on Mars investigates whether the dream of new worlds won’t create nightmares, both for settlers and the people they leave behind. In the process, the Weinersmiths answer every question about space you’ve ever wondered about, and many you’ve never considered:

Can you make babies in space? Should corporations govern space settlements? What about space war? Are we headed for a housing crisis on the Moon’s Peaks of Eternal Light—and what happens if you’re left in the Craters of Eternal Darkness? Why do astronauts love taco sauce? Speaking of meals, what’s the legal status of space cannibalism?

With deep expertise, a winning sense of humor, and art from the beloved creator of Saturday Morning Breakfast Cereal, the Weinersmiths investigate perhaps the biggest questions humanity will ever ask itself—whether and how to become multiplanetary.

Get in, we’re going to Mars.

Author

© Zach Weinersmith
Dr. Kelly Weinersmith received her PhD in Ecology at the University of California Davis, and is an adjunct faculty member in the BioSciences Department at Rice University. Kelly studies parasites that manipulate the behavior of their hosts, and her research has been featured in The Atlantic, National Geographic, BBC World, Science, and Nature. When she isn't studying Nature's creepiest wonders, Kelly is writing books with her husband, Zach Weinersmith (creator of Saturday Morning Breakfast Cereal Comics). Their first book, Soonish: Ten Emerging Technologies That'll Improve and/or Ruin Everything, was a New York Times Bestseller. View titles by Kelly Weinersmith
© Zach Weinersmith
Zach Weinersmith is the cartoonist behind the popular geek webcomic, Saturday Morning Breakfast Cereal. He co-wrote the New York Times bestseller Soonish: Ten Emerging Technologies That'll Improve and/or Ruin Everything and illustrated the New York Times-bestselling Open Borders: The Science and Ethics of Immigration. His work has been featured by The Economist, The Wall Street Journal, Slate, Forbes, Science Friday, Foreign Policy, PBS, Boingboing, the Freakonomics Blog, the RadioLab blog, Entertainment Weekly, Mother Jones, CNN, Discovery Magazine, Nautilus and more. He lives in Virginia with his wife/coauthor and his children/coauthors. View titles by Zach Weinersmith

Excerpt

1.

A Preamble on Space Myths

Idyllic views of the future always seem to come with the hidden assumption that human nature will change. That somehow, the flaws of mankind will just melt away amongst the awesomeness of living among the stars. People will abandon mundane flaws like booze and drugs, and also everyone will be super-efficient like some kind of environmentalist's dream. But that's never been the case as we march forward, so I don't see why it would happen in the future.
Andy Weir, world famous sci-fi author who also writes really insightful commentary in books about booze in space. 


Outlandish ideas about space settlement often function as a justification for the whole project, typically promising vast wealth, an improved humanity, or an escape from Earth-awfulness. Because much of this book hinges on the idea that there is no urgent need to settle space, here we'll try to convince you that most of the pro-settlement arguments are wrong. Some of these arguments may be unfamiliar to you, but all of them have at least some powerful advocates in government, military, or business settings.

Bad Arguments for Space Settlement

Argument 1: Space Will Save Humanity from Near-Term Calamity by Providing a New Home

The idea of a multiplanetary humanity as more resilient to extinction is a common one and is plausible over the very long term. However, over the short term, space settlement won't help with any catastrophe you're imagining right this second. Not global warming, not nuclear war, not overpopulation, probably not even a dinosaur-style asteroid event. Why? In short, because space is so terrible that in order to be a better option than Earth, one calamity won't do. An Earth with climate change and nuclear war and, like, zombies and werewolves is still a way better place than Mars. Staying alive on Earth requires fire and a pointy stick. Staying alive in space will require all sorts of high-tech gadgets we can barely manufacture on Earth. We'll elaborate on all of this over the course of the book, but the basic deal is that no off-world settlement anytime remotely soon will be able to survive the loss of Earth. Getting any kind of large settlement going will be hard enough, but economic independence may require millions of people.

We believe there's a decent case for a Plan B reserve of humanity off-world, but there isn't a good case for trying to do it fast. A commonly made argument for urgency is what's sometimes called the "short-window" argument. The idea is that historically, "golden ages" don't last long, so our current age of space travel might come to an end before we get to Mars. We don't know if that's a good analysis of history, but what we can say is that the current age is simply not golden enough to deliver an independent Mars economy. If you want a Mars that can survive the death of Earth, you'd better make sure Earth doesn't die for a very long time.

Weinersmith Verdict: Nah.

Argument 2: Space Settlement Will Save Earth's Environment by Relocating Industry and Population Off-World

There are various flavors of this argument, many of which are popular with the rotating-space-station settlement community, including Jeff Bezos.

One version of this idea is that the solar system contains more than enough mass to create rotating space stations that can accommodate an almost endless number of humans in space. This is literally possible in the sense that there is lots of stuff in space, and the stuff could be refashioned into space bases, but we need a sense of proportion here. The Earth of 2022 puts on about 80 million people per year. If saving our ecology requires us to reduce Earth's human population, then we need to launch and house 220,000 volunteers per day just to tread water.

A related idea is that space should be zoned for heavy industry, while Earth returns to an unpolluted Edenic state. All the nasty mining and manufacturing can be done elsewhere, with by-products cleanly disposed of into the vast landfill that is the solar system. As Jeff Bezos says, "Earth will be zoned residential and light industrial." Again, this is literally possible, and perhaps as long as you're just thinking in terms of big concepts like pollution and mass it sounds doable. But the details are where the difficulty lives. Consider for example cement. It's a major contributor to global warming, so can we make it in space?

Technically, most of the components of cement by mass exist on the Moon, but they won't be easy to dig up. Construction equipment will need to be built to function in an airless environment at low gravity with equatorial temperature swings from -130°C to 120°C. Little things start to loom in this context. Just getting a lubricant that can handle these temperature shifts without degrading is nearly impossible. The same goes for the machines themselves. At extreme cold some metals can undergo a ductile-to-brittle transition; below a certain temperature, metals behave more like stone. However strong they may be, they can't flex and bend. It's speculated that the Titanic sank because its steel hull experienced a ductile-to-brittle transition before hitting the infamous iceberg. That's a nontrivial problem when you desire to use construction equipment that regularly slams into hard surfaces.

And that's just one detail of one part of the process, never mind replicating all those factories. How soon can we plausibly get all these problems solved and then scaled to the needs of Earth, which currently requires over 3.5 billion metric tons of cement per year? And does it sound economically competitive with Earth-made cement even if we could do it? And, by the way, what are the rules for dropping 3.5 billion tons of rock on Earth annually?

Part of what's supposed to make these ideas work is cheap, plentiful energy thanks to space-based solar power. This is another bad idea. Space-based solar power figures prominently in space-settlement proposals for giant rotating space stations. It's also frequently proposed by governments and private space companies as a way to make money while greening the planet. You may have read an article recently about Chinese universities or the European Space Agency, or some new start-up planning to field this technology in the near future. They probably shouldn't.

It's certainly true that there's a whole Sun's worth of sunlight in space, unobstructed by annoying Earth features like weather and the atmosphere. Exactly how much more energy you might get per panel depends on exactly what assumptions you're prepared to make, but different estimates expect about an order of magnitude improvement. That sounds like a lot until you ask yourself what the cost differential will be between a panel in space and a panel in Australia.

It's conceivable that in a world where solar panels are incredibly expensive and there's an extreme collapse in the cost of launching objects to space, you might want to maximize your energy per panel by putting them above the atmosphere. But panels are cheap, and even if we assume pretty steep drops in the cost of space launch, the numbers don't add up. This becomes especially clear when you start to think about maintenance. Try to imagine acres upon acres of glass panels in space, regularly pelted by intense radiation and bits of space debris while enduring the extreme heat of perpetual sunlight. They'll have to be repaired and cared for either by astronauts or an army of advanced robots. Solar panels in Australia can be cleaned by a teenager with a squeegee.

When dumping solar power back to Earth, you have another problem. Solar panels on the ground can send their power right into the grid or to batteries. Space-based power has to be beamed to huge receivers on Earth, losing energy en route. But it can't be beamed at too high an intensity, lest it endanger birds and planes.

Space solar is valuable if you're already in space, as a way to generate energy without burning fuel. It may also be valuable on Earth in some very narrow cases, such as beaming energy to military bases where fossil fuel delivery would be dangerous. For more practical uses, you're better off with conventional boring renewables. Cover every rooftop with solar panels, followed by the Sahara desert, and then if the planet still needs energy, we can talk about space.

We are skeptical that it will ever be a great financial idea to harvest massive amounts of solar power in space and then use that energy to convert moondust into cement or steel or industrial chemicals. But even if we believe that this'll all happen one day, that one day will not come in time to spare us from any environmental concern of today.

Weinersmith Verdict: Unfortunately, no. 

Argument 3: Space Resources Will Make Us All Rich

It's certainly possible, but right now the economics of it aren't looking great. As we'll explore later, no place in space has something like a giant hunk of pure platinum or gold. What space resources do exist are likely to be very expensive to acquire and will remain so even with big improvements in technology.

Also, there's a real difference between access to commodities and universal wealth. Consider aluminum. Discovered in 1825, early on it was so valuable that only the wealthy could afford it. Victorian-era jewelry sometimes includes aluminum as a precious metal. Today, it's a way to cover lasagna. That's because by the late nineteenth century, industrial processes had made aluminum incredibly cheap, effectively flooding the market with a former luxury good. This is a great development, and of course aluminum has uncountable valuable applications from the kitchen to airplanes. But the fact that most of us can buy large quantities of a once-precious metal doesn't mean we're all millionaires.

In our experience, people tend to assume raw minerals are the major factor in human well-being. Although they're necessary inputs into our economies, according to a recent report by the World Bank, nonrenewable resources, in the sense of valuable stuff found in the ground, make up about 2.5 percent of Earth's wealth. And a lot of that is fossil fuels, which are not available in space. The really valuable thing for economies is humans, and our ideas and technology. You can convince yourself by melting down your phone and assessing the value of the resulting glass, metal, and plastic.

Even if space does produce inexpensive access to all sorts of commodities that make someone rich, there's also no reason to assume anything like an equal distribution of wealth back on Earth. In fact, if you believe there's big money in space, the United States is uniquely poised to go get it, potentially harming the economies of less-developed countries dependent on commodities. Some readers will care about this more than others, but even if you don't think wealth distribution has much moral significance, it may still have geopolitical significance. As we'll see later, under some conditions, changes in the balance of power among nations can make war more likely. If space really does make some country especially rich, the consequences don't have to be uniformly good.

Weinersmith Verdict: It's complicated but no, not really. 

Argument 4: Space Settlement Will End, or at Least Mitigate, War


There are a few versions of this one, but we've found these three pretty common: space settlement will create more territory so we'll fight less about territory; space settlement will make us rich so we won't want to fight anymore; and space settlement will allow unhappy citizens to just leave for other settlements, which will reduce tension here on Earth.

The territory argument is the most silly. Nations don't fight over land, they fight over particular land. You can't solve disputes over Jerusalem or Kashmir or Crimea by promising the parties involved equally large stretches of Antarctica. It'd be like going to a nasty divorce proceeding and trying to solve the custody fight by offering to just grab some other kids. Also, if we're defining land as "built structures humans live in," which is the definition you must use for space habitats, well then, on Earth we are creating land all the time. Individual buildings create far more square footage than any space settlement likely to be built anytime soon. Meanwhile, if you personally just want any sort of land there's plenty. Google it. Small towns all over the developed world are offering free land to people willing to move there instead of big cities.

The argument about riches may sound tempting; if humans are rich, why would we fight? But the "money makes us all friends" argument isn't one that all war scholars buy. Wars start for all sorts of reasons that have nothing to do with a bunch of people looking at their resource base and saying "hey, this is pretty good." A nonexhaustive list of causes of war includes: religious differences, leaders who don't bear the cost of the violence, and misperception about the other party's strengths or intentions. Even if space activity left everyone better off, it wouldn't stop nations from having religious differences, bad leaders, or suspicion about rivals.

As for peace through allowing people to just move between settlements, well, we should consider that most people aren't even allowed to do this between nations on Earth. Space will likely be worse. However you feel about immigrants coming to your country, one thing you probably don't fear is the possibility that they'll breathe too much air. In space, the atmosphere is constructed, as is the ground beneath your feet, and individual settlements will only be rated for certain population sizes. That's not obviously an environment where you'd expect to see open borders. Some advocates note that you can always just create a new place to live in space, but then the argument becomes "you can just pull up stakes by creating a million-ton space station," which, we suspect, will not be a live option for most of us. Even if it were, it's still not clearly desirable. Dr. De Witt Kilgore, one of the few historiographers of ideas about space, called it a form of celestial "white flight." That is, space not as a solution to politics, but as an escape from political realities one group finds uncomfortable.

Weinersmith Verdict: Nope.

Argument 5: Space Exploration Is a Natural Human Urge

This is a popular one. The basic idea is that yeah, maybe there's not a good return-on-investment reason for space exploration, but if we don't do it, we'll be thwarting our own nature, resulting in widespread human stagnation. The prettiest version of this argument is of course from Dr. Carl Sagan: "For all its material advantages, the sedentary life has left us edgy, unfulfilled. Even after 400 generations in villages and cities, we haven't forgotten. The open road still softly calls, like a nearly forgotten song of childhood." It's a nice idea, and much better written than any of our Uranus jokes. Also, it can be hard to argue against views like these because it's not always clear what the exact claim is. However, when people do get specific, they tend to point to two things: famous human explorers, and the fact that humans have spread around the world.

Praise

“This playful ‘homesteader’s guide’ to space settlement presents a bleak view of the pursuit . . . The authors examine the increasingly popular dream of a multi-planetary human race with a skepticism informed by ethical, logistical, and legal anxieties.” The New Yorker

“A wonderful example of what it means to really think a difficult project through, a skill that many of us should acquire . . . The Weinersmiths are self-confessed space geeks who tread a fine line between the sort of constructive critique that would still qualify them as bona fide members of the space-settlement movement and a style of gentle ridicule that might get them rejected as traitors to the cause. A City on Mars is, foremost, a case study in the application of common sense.” —Shlomo Angel, Wall Street Journal

“An exceptional new piece of popular science . . . Forceful, engaging and funny… an essential reality check for anyone who has ever looked for home in the night sky . . . hilarious. The breezy prose is studded with charming cartoons . . . This book will make you happy to live on this planet—a good thing, because you’re not leaving anytime soon.” New York Times Book Review

“Engaging . . . breezy . . . honest yet hilarious . . . delightful cartoons sprinkled throughout the book are sure to pull chuckles out of you.” —Space.com

“Laced with humor but with a real gut punch . . . a fascinating book, packed full of racy space stories, that raises serious questions about the future of human space travel and settlement.” The Explorers Journal
 
“Laugh-out-loud-funny.” Scientific American
 
“Excellent . . . sets out persuasively and amusingly why you would have to be wildly optimistic or crushingly stupid to want to set up a space settlement any time soon.” —Stephen Bush, FT

“Mix of expertise and humor . . . In a world hurtling toward human expansion into space, A City on Mars investigates whether the dream of new worlds won’t create nightmares, both for settlers and the people they leave behind.” —Daily Kos

“The Weinersmiths artfully encourage readers to entertain the thought of living on Mars while skillfully highlighting the absurdity of such a prospect through compelling data and delving into serious questions all through a lighthearted lens . . . [this] tongue-in-cheek narrative will captivate even the skeptics, directing their gaze upward at night.” —Debbra Palmer, The New York Journal of Books

“Helpfully pulls back the curtain . . . painstaking research, clear-eyed objectivity, and good-natured humor . . . Any reader enthusiastic about space settlement will find much to appreciate in this book . . . most importantly, they write with a confident belief that humanity will one day travel off-planet.” Gifford J. Wong, Science
 
“A sobering book, but also, ultimately, a hopeful one—and perhaps recommended reading for lots of sci-fi fans out there.” —Charles Bonkowsky, Tor.com (Reviewers’ Choice, Best Books of 2023)

“Hilarious, highly informative and cheeky book . . . use[s] humor and science to douse techno dreams with a dose of reality . . . Even as they shoot down a long list of space fantasies, they explore a lot of really interesting research.” —Christie Aschwanden, Undark

“Entertaining and informative romp through what’s stopping us from moving off-planet . . . Well researched and argued, it’s also a very fun read.” —Jennifer Rothschild, Arlington Magazine

“Full of some of the choice-iest bits of awkward human space exploration histories and theories . . . could have been the research notes for an Ursula K. Le Guin, or a James S. A. Corey story, except that it’s filled with jokes, palette cleansing anecdotes and charming cartoon illustrations . . . a popular science book that reads like a conversation with a friend . . . you can’t get away from this book without thinking about how precious life on Earth is.” —Mark Popinchalk, Astrobites

“Science writing is rarely as readable (or deflating) as A City on Mars, an informed, irreverent study of how little we actually know of the practical considerations of space colonization, from sex and legal cannibalism to issues of settlement.” Chicago Tribune, 75 Top Picks for Fall

“Starting life anew somewhere far, far away sounds appealing. But that fantasy is so much further from realization than we think, argues this wife-and-husband-team persuasively.” MIT Tech Review

“Inventive, funny, and informative . . . Filled with fun illustrations that bring the writing to life, this accessible and thought-provoking book explores what it will really take to build a society on another planet.” American Scientist

“[A] romp through the many rooms of space folly… amusingly literal and impeccably scientific”—Stuart Jeffries, The Guardian, Book of the Day (UK)

“A very funny book, underpinned by deadly serious questions about the future of humanity.” —Ben Spencer, 19 Best Science and Environment Books of 2023, The Times (UK)

“This witty and wildly informative guide to space colonization boldly goes where few books have gone before . . . engaging, wildly informative, insightful, and frequently funny.” —Rhys Blakely, The Sunday Times, Book of the Week (UK)
 
"Rich food for rocketheads and critics alike. Kelly and Zach Weinersmith bring tough love to the idea of Martian settlement in A City on Mars, a sharp, well-informed and very funny book."Simon Ings, The New Scientist, Best Books of 2023 (UK)
 
"Is living off-world not the ultimate insurance policy for our species? A City on Mars... answers this question very bluntly: don't pin your hopes on it ... peppered with cartoons and jokey-back references, and between each section are interludes tackling some enjoyable anecdotes from space"James Ball, The Spectator (UK)
 
"Informative and entertaining"Andrew Crumey, Literary Review (UK)
 
"Manages to be at the same time informative, sceptical and hilarious"Engineering and Technology, Books of the Year

“Wickedly irreverent . . . The cheeky tone is loads of fun, and Zach’s humorous illustrations of, for instance, contraptions proposed to facilitate zero-gravity sex, entertain . . . A boisterous takedown of techno-utopianism.” Publishers Weekly (starred review)

“Immersive and entertaining . . . the Weinersmiths' passion and enthusiasm shine through every page of this absorbing, lively exploration.” Booklist (starred review)

“An entertaining illustrated assessment of space settlement. This book is, to put it simply, a romp . . . A fun, informative read that puts the pop into popular science.” Kirkus

“There is simply no more engrossing, entertaining, or thorough way to understand the intense challenge of humanity's off-Earth future than A City on Mars. I laughed the whole way through.” —Hank Green, New York Times bestselling author of An Absolutely Remarkable Thing and host of CrashCourse and SciShow

“Scientific, educational, and fun as hell.”—Andy Weir, New York Times bestselling author of The Martian and Project Hail Mary 

“Listen up, humans. How to poop in space will be the least of our concerns. Herein are challenges most space-heads, including me, never even considered: not just technological, but legal, ethical, geopolitical.  Despite the breadth and depth of research and some impressive near-wonk-level detail, this is a clear, lively, and hilarious read.  Slam dunk, Weinersmiths!"—Mary Roach, New York Times bestselling author of Fuzz and Packing for Mars

“A must-read!” Jonathan McDowell, Center for Astrophysics, via X

“This might be the best book ever written about humans in space, or at least the funniest. I don't know of anything else quite like it: an extended, comical confrontation between the dreams of space colonies and the gross, dangerous, tedious realities. Read it before you go.” —Scott Aaronson, Schlumberger Chair of Computer Science and Director of Quantum Information Center, University of Texas at Austin

"Of the many books and extensive literature on Space mission architectures, technical and otherwise, this is the only one that is a must-read to understand the deep financial, physiological and technical constraints of one of the largest and most ambitious endeavors of our time: enabling humans to become a multi-planetary species.” —Professor Sinead O'Sullivan, member of the Advisory Council of the European Space Policy Institute

“A fun, and sobering, exploration of what it means to explore beyond our planetary home. Sure, the stars beckon and TV shows and movies make space travel seem like a blast, but before you invest in another billionaire’s crypto-powered Mars colonization dream, you might want to pick up this book and learn about the risks, astronomical costs and thorny ethical issues involved. The Weinersmiths take you on a journey to our unlikely future on other planets with impressive detail, eye-opening facts, and extremely funny cartoons.” —Jorge Cham, author of Oliver’s Great Big Universe and creator of PHD Comics

“Earth may not be perfect, but we evolved here. Everywhere else in the Universe will try heartily to kill you in nasty ways. The Weinersmiths logically and patiently lay out the case that if we want to live in space, there's a lot of ground work to do first. If you're a gung-ho Moon and Mars enthusiast, this book will show you why it's best to slow down the space race just a bit.”—Phil Plait, writer of the “Bad Astronomy Newsletter”

“A City on Mars is deeply researched, hilarious, and sobering. Zach and Kelly Weinersmith have given us a bracing to-do list for the new age of space. Highly, highly recommended.” —James S.A. Corey, author of The Expanse series

“A refreshing, clear-headed breath of life-support oxygen amidst all the tech-bro naivety and hype on space colonisation. Impeccably researched and argued, yet witty and very easy to read. Superb!” —Professor Lewis Dartnell, New York Times bestselling author of Being Human

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