A City on Mars: Can we settle space, should we settle space, and have we really thought this through?
A clear-eyed check on plans to settle the Moon, Mars or orbiting stations. It shows why habitats, childbirth and space law remain unsolved, and why our earthly problems would travel with us.

Table of Content
1. Introduction
59 sec
If you have ever read the news and wished humanity had a second planet, the authors of A City on Mars have a sobering answer: we are nowhere near ready, and leaving would not leave our troubles behind. Biologist Kelly Weinersmith and cartoonist Zach Weinersmith take the billionaire promises of Martian holidays seriously enough to check them, piece by piece. Launch prices have fallen, they point out, but space is as deadly as it ever was.
Their case is that settling space is far harder than its promoters admit. The questions few people like to ask, about bodies, babies, shelter and law, are still open, and any settlement would stay tied to Earth and its conflicts. That does not make the authors enemies of space travel. It makes them advocates of going slowly.
Follow their reasoning and you gain a sharp set of questions for any bold vision, whether it comes from a rocket company or from your own leadership team.
2. Spot the weak reasons for leaving Earth
2 min 10 sec
Escape, world peace and cosmic treasure are the usual reasons given for settling other worlds. A Victorian luxury that ended up in kitchen drawers suggests why most of them fall apart under a closer look.
3. Every nearby destination is poor real estate
2 min 05 sec
The Moon is close, Mars feels familiar and a spinning station sounds like a dream home. Each option hides a daily hazard that would shape every hour of a settler’s life, and none of them shows up in the brochures.
4. Life on another world means bunkers, not domes
2 min 09 sec
Films show settlers strolling through sunlit gardens under glass. The real picture involves recycled waste, buried shelters and a famous Arizona experiment where the hardest problem to manage turned out to be the crew itself.
5. Babies are the problem settlement cannot skip
2 min 09 sec
A colony that cannot raise children will not last a generation. What happened to animals conceived beyond Earth raises a question that rapid colonization plans tend to wave away, and the proposed fixes raise harder ones.
6. See where space law could spark a conflict
2 min 17 sec
A treaty written in 1967 still governs who may own, mine or fight over the heavens. Its vague wording has already let nations and private citizens push its limits, and the coming rush of traffic will test it far harder.
7. Conclusion
1 min 25 sec
What the Weinersmiths finally hold up is a mirror. People look at Mars hoping to leave climate, politics and war behind, and the closer the authors look, the more those same things reappear: power struggles in a sealed Arizona greenhouse, nations testing loopholes in a 1967 treaty, riches that would flow to a few. Space, in their telling, shows us ourselves, troubles included.
That is no argument against going. The authors accept two honest reasons, a hedge against threats to our species and the human drive to explore, and they think technology may one day make space a refuge, though never a rescue. What they reject is speed dressed up as vision.
Their habits of mind are worth keeping on the ground too. When a bold plan arrives, ask which of its reasons survive a hard look and which only sound thrilling. Picture the daily conditions behind the glossy image: the toxic dust, the recycled water, eight tired people with no privacy. Treat missing evidence of harm as a call for more study, the way the authors ask for rodent colonies and more women in orbit before anyone plans space babies. And settle the rules before the stakes climb.
Wherever we go, we bring ourselves along. The wise move is to be ready for that company.
About this book
What is this book about?
Rocket launches are getting cheaper, billionaire-led companies promise settlements on Mars, and a planet weighed down by climate change, political turmoil and war makes leaving sound tempting. Kelly and Zach Weinersmith take those promises seriously enough to check them, one at a time. They start by testing the popular reasons for going, from escaping Earth's troubles to ending war and striking it rich, and find that only two hold up: making our species more resilient and our urge to explore. Then they look at what settlers would actually face. The Moon has abrasive dust, Mars has toxic soil and planet-wide storms, and spinning stations would be wobbly and expensive. Settlers would live in radiation-shielded bunkers, recycle their own waste and argue like the crew of Biosphere 2. Animal studies point to serious risks for children conceived in space, and a 1967 treaty leaves gaps that powerful nations already exploit. The authors are not against space. They argue for going slowly and settling the hard questions first. Readers get a sharp, often funny reality check, and a habit of asking hard questions that works on any bold plan.
Book Information
Who it's for
Looking past Mars headlines
Space fans who want an honest look behind the Mars headlines.
Professionals judging bold plans
Professionals who judge bold plans and want sharper questions for any grand vision.
Students and the curious
Students and curious readers interested in the biology, ethics and law of living beyond Earth.
About the Author
Kelly Weinersmith
Kelly Weinersmith is a biologist on the BioSciences faculty at Rice University who studies parasites that change their hosts' behavior, and she co-hosts the podcast Science...sort of. Her work has been covered by The Atlantic, National Geographic, Science and Nature. Zach Weinersmith created the award-winning webcomic Saturday Morning Breakfast Cereal and co-founded the sketch group SMBC Theater. The married pair also wrote the science book Soonish together.
Ratings & Reviews
Ratings at a glance
What people think
Listeners find this work highly educational and supported by top-tier research, while also appreciating the humor woven into its various quips and stories. Additionally, the prose is skillfully composed, offering an experience that is both engaging and mentally stimulating. However, perspectives on space exploration are divided; the content encourages reflection on the realities of colonization, though some describe the outlook as disheartening. There is also mixed feedback regarding the difficulty, as one listener notes it is not too challenging for non-science readers, while others find the material demanding.
Top reviews
A bucket of ice-cold reality dumped straight onto our collective sci-fi daydreams. Kelly and Zach Weinersmith do something rare in popular science: they dismantle the romantic narrative of near-future space colonies without sounding like joyless scolds. The book walks you through every gruesome logistical hurdle, from the biological nightmare of gestating human fetuses in microgravity to the grim reality of breathing recycled air inside pitch-black lava tubes. Honestly, the chapter exploring hypothetical space cannibalism had me laughing out loud while simultaneously feeling mildly nauseated. Zach’s witty cartoons provide the perfect visual palate cleanser between dense discussions of closed-loop biospheres and the Outer Space Treaty. It turns out that living on Mars wouldn’t be an inspiring frontier adventure; it would be surviving in a freezing, toxic gravel pit governed like a miserable corporate company town. Essential reading for anyone who thinks escaping to the stars is easier than fixing the planet we already have.
Show moreThe breakdown of why human biology fundamentally rejects space living was equal parts terrifying and deeply fascinating. Everyone loves talking about sleek spaceships and high-tech Martian domes, but nobody stops to think about the horror of razor-sharp regolith or cosmic radiation frying your DNA. Kelly Weinersmith’s scientific background shines brightly here, offering sober clarity where Silicon Valley tech moguls usually offer empty promises. I particularly appreciated the frank exploration of self-sustaining ecosystems and our historic, embarrassing failures to build closed biospheres even right here in Arizona. The writing strikes a brilliant balance between academic rigor and irreverent silliness, complete with ridiculous footnotes that genuinely made me chuckle. Space is not our future backup drive; it is an unforgiving void that wants to crush, freeze, or irradiate squishy humans instantly. This is a brilliant, thought-provoking reality check that every futurist needs on their shelf.
Show moreZach’s trademark SMBC wit paired with Kelly’s meticulous biological expertise makes for an absolute masterclass in science communication. They examine the entire dream of space colonization and systematically reveal just how absurdly underprepared humanity truly is. From the hilarious yet disturbing reality of space cannibalism protocols to the nightmare of raising infants in reduced gravity, every chapter delivers eye-opening insights. What surprised me most was the extensive coverage of legal frameworks; learning how ambiguous property rights could accidentally trigger World War III over a lunar crater was riveting. The book doesn't say we should never explore outer space, but rather that we need to grow up significantly before attempting it. Smart, hilarious, and impeccably researched from beginning to end.
Show moreForget the glossy brochures advertising Martian vistas and luxury biodomes; this book is here to remind you that space smells like unwashed gym socks and wants to kill you. The Weinersmiths tackle space expansion not as an inevitable heroic triumph, but as a deeply flawed premise riddled with unaddressed biological, legal, and sociological traps. I loved how fearlessly the authors poked fun at corporate vanity projects while providing serious, peer-reviewed data on radiation sickness, closed-loop farming, and governance. The cartoons scattered throughout are laugh-out-loud funny and help leaven the sobering realization that living off-planet would essentially mean dwelling in cramped, subterranean basements. It completely reframed my perspective on space settlement in the best possible way.
Show morePicked this up after seeing a recommendation on Bluesky, expecting a quick romp through rocket science. Instead, I got an unexpectedly thorough education on geopolitics, municipal infrastructure, and why space reproduction is an absolute biomechanical catastrophe. The authors make a compelling case that our grandest obstacles off-Earth aren't just propulsion systems, but human biology and international law. We simply do not understand how partial gravity affects long-term human gestation or child development, which makes permanent settlements ethically dubious right now. To be fair, the extended deep-dive into territorial governance and resource-claim disputes dragged quite a bit during the book's second half. My attention definitely wavered when the discussion shifted from exploding space toilets to dry legal definitions. Still, the charming illustrations and sharp prose keep the heavy topics remarkably accessible.
Show moreWhy is everyone pretending we are five minutes away from building functioning suburbs on Mars? Zach and Kelly Weinersmith cut right through the venture-capital marketing fog to ask the basic, unglamorous questions that nobody else seems willing to address. What happens when your oxygen supplier decides to raise prices? Who owns the only frozen crater containing drinkable water? If a crime happens in a shared habitat, under whose jurisdiction does the offender fall? The authors argue convincingly that humanity lacks the ethical maturity and technological maturity to build off-world societies without reproducing our worst colonial impulses. In my experience with popular science books, authors usually default to breathless cheerleading, so this deeply skeptical perspective was immensely refreshing. Packed with sharp wit and memorable cartoons, this is a phenomenal read.
Show moreNot gonna lie, I was slightly depressed by chapter five after realizing just how utterly uninhabitable our solar system really is. We have all grown up watching sci-fi films depicting sleek space stations and bustling lunar colonies, but the reality is that Mars is an irradiated hellscape with toxic dirt that will ruin your lungs. The Weinersmiths do an exceptional job of explaining complex biological and engineering barriers without ever talking down to the reader. That being said, the extensive middle section covering international space treaties and territorial sovereignty felt a bit sluggish compared to the punchy science chapters. Even so, the authors deliver a desperately needed message: Earth is an astonishing paradise, and throwing trillions of dollars at space escape pods while our own home burns is absolute madness.
Show moreCall me a romantic, but this book felt like an exhausting buzzkill. While I appreciate the monumental amount of research the authors poured into this volume, their insistence on snarky punchlines wore thin by the third chapter. It reads less like an objective scientific investigation and more like a lengthy podcast script desperate to keep teenagers entertained. The central argument—that settling space right now is foolish, expensive, and legally messy—is hammered into the ground repeatedly across hundreds of pages. You get the point long before you reach the exhaustive chapters parsing archaic maritime law and UN treaties. Look, the scientific warnings about bone density loss and failed closed-loop biospheres are undeniably solid. However, the relentlessly pessimistic perspective completely saps the wonder out of human exploration.
Show moreThis book offers a desperately needed reality check, yet it occasionally swerves into exhausting pedantry. There is no denying the depth of scholarship on display; the authors consulted countless specialists and combed through obscure international treaties to construct their arguments. However, their insistence that humanity cannot possibly overcome engineering barriers feels overly fatalistic at points. We went from Kitty Hawk to the Moon landing in sixty-six years, yet the authors treat current low-gravity health risks as practically insurmountable dead ends. The audio version also felt somewhat frantic, as the humorous interjections and footnotes broke up the narrative flow a bit too frequently. Still, if you want a detailed look at the legal and physiological nightmares awaiting future astronauts, it provides plenty of food for thought.
Show moreAs an aerospace technician, I went in hoping for rigorous technical solutions, but found an overly cynical pop-culture critique instead. The authors build their entire premise around a strawman argument that private billionaires are somehow on the verge of carelessly launching millions of civilians to Mars tomorrow. To make their case, they repeatedly lean into juvenile jokes and alarmist hypotheticals rather than engaging seriously with emerging engineering milestones. They spend dozens of tedious pages agonizing over international space treaties, treating outdated bureaucratic paperwork as an insurmountable barrier rather than an evolving legal framework. Frankly, dismissing decades of robotic manufacturing advancements and orbital research as futile nonsense felt disingenuous. While the chapters covering radiation shielding and low-gravity muscle atrophy contain valid reminders of human fragility, the overall tone is relentlessly smug. If you want serious astronautics analysis, look elsewhere.
Show moreQuestions about this book
What is the main argument of A City on Mars?
Kelly and Zach Weinersmith argue that settling space is far harder than its promoters admit. Habitats would need heavy shielding and closed recycling systems, reproduction in space carries serious unknown risks, and space law is vague. Since any settlement would depend on Earth, our conflicts would follow us. They still allow that measured expansion could make sense, and they urge a slow, careful approach.
Do the Weinersmiths think Mars or the Moon is the better place to settle?
Neither is easy. The Moon is close and has resources, but its abrasive dust, radiation and extreme temperatures are dangerous. Mars has water, carbon and Earth-like days, but its dust contains toxic perchlorate, storms can block sunlight for weeks and Earth is half a year away. Rotating stations are attractive but costly and unstable at small sizes.
Is it safe to have children in space according to A City on Mars?
The authors say we simply do not know, and the evidence so far is worrying. Radiation and missing gravity affect embryos and cells, and animal studies on mice, rats, salamanders and quails show more abnormalities and deaths in offspring. They call for long-term animal studies, more female astronauts, artificial gravity and radiation protection before attempting it.
What are good reasons to settle space according to the book?
After rejecting escape from Earth’s problems, ending war and getting rich from rare minerals, the authors accept two reasons: making humanity more resilient against long-term threats to its existence, and the human desire to explore. Even these, they argue, require careful governance and a realistic view of the costs.
How can I apply the ideas in A City on Mars?
The book’s way of thinking works on any ambitious plan. Separate the reasons that hold up from the merely exciting ones. Look at daily conditions rather than the best feature. Treat a lack of evidence of harm as a reason to study more. And set clear rules early, as the book’s look at the vague 1967 Outer Space Treaty shows.
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