Before he rocketed off to spend a year in space , one of Scott Kelly ’s final acts on Earth was peeing on the back tire of a van. Not because you can’t pee in space (you can—it just requires some suction). It’s tradition: Yuri Gagarin, who made it to space first, did the same thing. In Kelly’s new book, Endurance , the veteran astronaut writes about that and all the other weird practices and rituals and anxieties and safety checks and responsibilities and more safety checks that go into preparing for, and then spending, a chunk of your life in perpetual free fall. The main takeaway: It’s hard. Coffee comes in plastic bags. Space smells funny. There’s never enough chocolate pudding. But these pesky truths, along with some extreme ennui, are something humans will have to confront if we ever hope to pack our bags and move to Mars.

WIRED: What did you miss most during your year on the International Space Station?

Kelly: Toward the end, I noticed little things were bothering me. Like sitting at a table and having to keep track of my spoon. But mostly what you miss is people. Friends and family. And weather. Even just the wind, rain, sun, going outside.

You probably had a lot of time to watch TV, though.

We watched Gravity in space, which was a pretty funny thing to do—like watching a movie of your house burning down while you’re inside of it. Watched The Martian . But really more CNN than anything else. That and football.

Endurance was the name of Antarctic explorer Ernest Shackleton’s ship—which was crushed by ice. Why name your book after it?

Shackleton was an inspiration to me—though it’s almost a negative comparison. I thought about my situation, and then what those guys had to go through, and that made me feel better.

I used to ride submarines for the Navy, and some of the experiences you describe reminded me of being locked away underwater. Occasionally I’m someplace where the right combination of smells—amine, diesel, farts—triggers a memory. Does the same thing happen to you?

I was touring the Harris County Jail, and there’s this room that smells like space station—combination of antiseptic, garbage, and body odor. You know how on Earth, with gravity, stuff tends to rise or fall depending on its weight compared to air? On the ISS , that doesn’t happen, so smells can kind of linger.

Meaning you’re just dragging your stink around with you?

Well, it’s not like people really smell that bad. We use deodorant, we wipe, rinse off, shower. But there’s a little body odor going on for sure. Mostly it’s just exercise clothes people wear for a couple weeks without washing.

Do you think humans can last long enough in space to get to Mars?

Yes. It will take something like 200 days to get there, then you spend a year on the surface, then it’s 200 days to get back. I think we can do that. The real challenge is going to be when you want to keep people in space for a couple of years. Based on my experience of ever-­increasing durations of spaceflights—from eight days to 13 days to 159 to 340—I think going into the two-year mark would be a big challenge, especially without artificial gravity. Returning to gravity would be profoundly difficult, physiologically.

Funding for the ISS is set to run out in 2024. Should it be sold to a private company ?

I have an attachment to the space station—I’d rather do that than let it fall into the Pacific Ocean. But I don’t think there’s a business case for it. A multi­billion-dollar investment in the ISS is not going to have a multi­billion-dollar return anytime soon.

We should use it as a construction dock for interplanetary spacecraft headed to Mars!

That’s kind of science-fiction-y. I don’t know the orbital mechanics of Mars very well, but the space station could just be in the wrong orbit. I’m thinking about the 51.6-degree inclination the ISS is on around the Earth. Just visualizing that against the plane of our solar system, I don’t think it would work well to go to Mars . To change the orbital inclination, you’d need a significant amount of propellant.

Do you think you could have stayed in space much longer?

There was one point where I aggravated a hernia and had to take Ativan, which is a ­muscle relaxer. But it’s also used as an anti­anxiety medication, and I definitely noticed that effect. I didn’t really care anymore. I think I told my flight surgeon that I could stay up there another year. But I doubt the feeling would’ve lasted.

Nick Stockton ( @StocktonSays ) writes about science for WIRED.

This article appears in the September issue. Subscribe now .

Grooming by Heather Cruce/La’Bella Mafia Agency