If you want to understand what it’s actually like to be an astronaut, skip the heroic NASA press releases. Forget the sleek, cinematic slow-motion walks toward a launchpad. Instead, you need to think about poop. Specifically, you need to think about how you handle it when there is no gravity to pull it away from your body. This is the messy, cramped, and occasionally gross reality that Mary Roach explores in her masterpiece, Packing for Mars.
Space is fake. At least, the version we see in movies is. In the real world, sending a human being into the void is less about "boldly going" and more about managing the biological inconveniences of being a leaky, smelly, fragile mammal. Roach spends the book investigating the "surreal life" of space flight, focusing on the stuff NASA usually keeps behind closed doors. She doesn't talk about rocket thrust or orbital mechanics. She talks about the psychological toll of being stuck in a room the size of a closet with people you might grow to loathe.
It's been years since it was first published, but the Packing for Mars book remains the definitive guide to the "human" side of the space race. As we get closer to actual crewed missions to the Red Planet, the questions Roach asked are becoming less theoretical and much more urgent.
The Zero-G Bathroom Crisis and Other Things Nobody Tells You
Space is mostly a series of engineering problems, but the biggest variable is the human. We are high-maintenance. We need specific temperatures, precise gas mixtures, and a way to get rid of waste. Roach dives deep into the history of the "waste management system," which is a polite way of saying the space toilet.
During the Apollo missions, things were... grim. Astronauts had to use plastic bags taped to their butts. It was a process that could take an hour and often resulted in "escapees" floating around the cabin. It sounds funny until you realize these men were the peak of American heroism, sitting in a tiny tin can with floating feces.
Roach talks to the engineers who spent decades trying to fix this. It’s not just about comfort; it's about safety. In a weightless environment, fluids don't behave. They stick to surfaces. They crawl up walls. This isn't just a gross-out factor; it's a genuine technological hurdle for long-term habitation on Mars. If you can't figure out the plumbing, you aren't going to survive a two-year round trip.
The Psychology of the Small Room
Have you ever been on a long road trip and started to hate the way your friend breathes? Now imagine that road trip lasts 500 days. You can't open the window. You can't leave. And your friend’s breathing is literally the only sound in the vacuum of space.
NASA's "behavioral health" researchers are obsessed with this. Roach highlights studies where people were locked in isolation chambers for months to see when they would snap. Most of the time, it wasn't a major disaster that broke them. It was small stuff. The way someone chewed. A repetitive joke. A lack of privacy.
In the Packing for Mars book, we learn about the Russian Mars500 project. They locked six men in a windowless mock-up of a spacecraft in Moscow for 520 days. They wanted to see if they’d kill each other. They didn't, but the psychological fatigue was profound. Some participants became sedentary and depressed, while others developed disrupted sleep cycles that made them "out of sync" with the rest of the crew. On a real mission, that kind of friction is lethal.
Why We Can't Just "Tough It Out"
There's a common misconception that astronauts are just "built different." We assume they have nerves of steel and can handle anything. While they are incredibly disciplined, biology doesn't care about your resume.
Take bone density. In space, your body decides it doesn't need a skeleton anymore. Because you aren't fighting gravity, your bones start shedding calcium. You're basically peeing out your skeleton. This is a massive problem for a Mars mission. If you spend six months getting there and step onto the Martian surface with the bones of an 80-year-old with osteoporosis, you’re going to break a leg the first time you stumble.
Roach looks at the "bed rest" studies where volunteers are paid to stay in bed for months at a time, tilted at a six-degree downward angle. This mimics the fluid shift that happens in space, where blood rushes to your head and your legs turn into "chicken legs." It sounds like a dream job—getting paid to lie down and watch TV—but it’s actually a nightmare. People lose muscle mass, their vision changes because of pressure on the optic nerve, and they become profoundly lethargic.
The Cadaver Factor
One of the more controversial chapters in the book involves the use of cadavers in crash testing. It’s a bit macabre, but Roach argues it’s necessary. To design a spacecraft that can land safely, you need to know exactly how much force a human body can take before it breaks.
You can't do that with a crash test dummy alone. Dummies are great, but they don't have the same "compliance" as a human body. So, researchers use donated bodies to test seat designs and landing impacts. It’s the kind of gritty, uncomfortable detail that makes Roach’s writing so human. She respects the sacrifice of the donors while acknowledging how bizarre the whole situation is.
The Mars Reality Check
A lot of the hype around Mars today, fueled by companies like SpaceX, focuses on the "how" of the rocket. We talk about Starship and methane fuel and orbital refilling. But we rarely talk about the "how" of the person.
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The Packing for Mars book forces us to reckon with the fact that we are evolved for Earth. Every part of our biology, from our inner ear to our digestive tract, expects 1G of gravity and a 24-hour light cycle. Mars has about 38% of Earth's gravity. We don't actually know what that does to a human over the long term. Can you carry a pregnancy to term in 0.38G? Probably not, according to some of the animal studies Roach cites.
NASA has spent decades researching these "human factors," and the results are often humbling. We aren't space-faring creatures yet. We are Earth creatures trying to cheat.
- Hygiene: In space, you don't shower. You use wet wipes and rinseless shampoo. For months. The smell is something astronauts frequently mention in their private journals, even if they don't talk about it on the live feed.
- Taste: Your sinuses get stuffed up in space because fluids don't drain. This makes food taste like cardboard. Astronauts crave spicy food—Tabasco sauce is one of the most requested items on the ISS.
- Motion Sickness: About half of all people who go to space get "space adaptation syndrome." You're basically puking while trying to pilot a multi-billion dollar machine.
Is It Worth It?
Roach doesn't give a simple "yes" or "no" to the question of whether we should go to Mars. Instead, she highlights the sheer, ridiculous audacity of the attempt. It’s a trillion-dollar gamble to send a few humans to a freezing, radioactive desert where the soil is toxic and there's nothing to breathe.
But there’s something beautiful in that. The effort required to keep a human alive in a place that wants to kill them is a testament to our ingenuity. We build these complex life-support systems just to preserve a few liters of water and a few pounds of oxygen.
Honestly, the book makes you appreciate Earth more than Mars. After reading about the "fecal bags" and the bone loss and the isolation, a walk in the park with some fresh air feels like the greatest luxury in the universe.
What Most People Miss
People think the hardest part of Mars is the radiation or the landing. Those are huge. But the hardest part might be the boredom. When you're in a tiny pod for months, and there's nothing to do but maintenance and basic science, your mind starts to wander.
Roach notes that during the Skylab missions in the 70s, the crew actually went on "strike." They were overworked and tired of being micromanaged by ground control. They turned off their radios for a day and just looked out the window. It was a reminder that you can't treat humans like machines. We need autonomy. We need a reason to get up that isn't just "following a checklist."
Your Next Steps Toward the Red Planet
If you're fascinated by the future of space travel, don't just watch the rocket launches. You need to understand the meat inside the machine.
- Read the source material. Pick up a copy of Packing for Mars. It’s a fast read, and honestly, it’s one of the funniest science books ever written. Mary Roach has a way of making "boring" research feel like a gossipy conversation at a bar.
- Follow the ISS research. The International Space Station is basically a long-term laboratory for the stuff Roach writes about. Look up the "Twins Study" involving Scott and Mark Kelly. It’s the most comprehensive look we have at what space does to human DNA.
- Check out the HI-SEAS missions. The Hawaii Space Exploration Analog and Simulation (HI-SEAS) is a habitat on a volcano in Hawaii that mimics the Martian surface. They do some incredible work on crew dynamics and food prep that mirrors the experiments in the book.
- Look into "Space Architecture." This is a real field. Designers are trying to figure out how to make habitats that don't drive people insane. It involves everything from lighting to the "acoustics of silence."
The Packing for Mars book isn't just about space. It's about what it means to be a human being. It’s about our limitations, our smells, our quirks, and our stubborn refusal to stay where we belong. Whether we ever actually set foot on Mars is almost secondary to the incredible, gross, and hilarious things we’ve done to try and get there.
Space is hard. Being a human in space is harder. And that’s exactly why it’s so fascinating.
Actionable Insight: If you're interested in the "human" side of tech, start looking at "User Experience" (UX) for extreme environments. The lessons learned from space toilets and astronaut isolation are currently being applied to submarine design, polar research stations, and even long-haul trucking. The science of keeping people sane in small spaces is a growing field with massive implications for life here on Earth.