Houston Matters

We still have a long, long way to go before there’s ever ‘A City on Mars’

Kelly and Zach Weinersmith discuss their new book, which throws a bit of a wet blanket on the idea of future space colonies.


An illustration from the cover of "A City on Mars," which explores the realities of colonizing another planet.
An illustration from the cover of “A City on Mars,” which explores the realities of colonizing another planet.


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With NASA's Artemis missions gearing up to take Americans back to the moon and eventually Mars and the recent successes of commercial space companies in reducing the cost of getting people and equipment into space, the idea of someday colonizing the moon or another planet might seem more realistic and near-term than ever before.

But is it?

A new book pumps the brakes a little. It's called A City on Mars: Can we settle space, should we settle space, and have we really thought this through?

It's written by a pair of former Houstonians, the husband-and-wife team of Kelly Weinersmith and Zach Weinersmith. Kelly is behavioral ecologist and adjunct professor in the BioSciences Department at Rice University. And Zach is the cartoonist behind the web comic Saturday Morning Breakfast Cereal.

In the audio above, Houston Matters producer Michael Hagerty talks with the Weinersmiths, and Kelly explains how living long term on another planet is so much different than anything we've done before in space.

“We know from Apollo that it’s safe to send a couple dudes to the moon for a couple weeks,” she said. “They come back, and they are generally are no worse for wear.”

But sending people to live on other celestial bodies for years or even multiple generations — that’s a whole different story. What scientists don’t know, for example, is the effect living in partial gravity for a couple decades or a lifetime and what that would do to a woman’s bones and whether she’d be able to have babies.

Former Houstonians Zach and Kelly Weinersmith are the authors of "A City on Mars."
Former Houstonians Zach and Kelly Weinersmith are the authors of “A City on Mars.”

“There’s concerns for the mom if hip bones get too weak, but then there’s also concerns for the children growing under partial gravity,” Kelly said. “Or, additionally, space has different radiation than we experience here on earth.”

Getting to Space Is Cheaper, But That’s Not Enough

So, while it’s an exciting development that a commercial company like SpaceX has drastically reduced the cost of getting things into space, a lot more has to happen, Zach says.

“It means you can just put more stuff in space — that helps,” he said. “But what we argue is the problem is no matter how much you scale these rockets, if you don’t have the basic science for human health, human reproduction, and for how to design ecosystems that can exist in sealed bubbles surrounded by death, then you can’t go.”

And conducting the science to do all that is decades worth of work, he says.

What We’ve Learned from the ISS…Might Be Irrelevant

But isn’t that what the International Space Station has been for — to study the long-term effects of space on humans? Kelly says that while that research has been helpful, it’s not exactly an apples-to-apples comparison. The ISS was probably created more for geo-political reasons she said. And the environment is different.

The International Space Station.

“The space station is orbiting below the magnetosphere,” she said. “So, out in space, you’d get exposed to different radiation in different doses than what the astronauts on the International Space Station get exposed to. So, even the people who stay up for a year, that’s not going to tell us what we need to know about babies developing their whole lives on the moon or Mars.”

A Good First Step

However, setting up colonies on the moon would be more informative and less risky.

“Because you can get to the moon in two or three days,” Kelly said. “So, if it turns out it’s not working, you jump back in your spaceship, and you come home. Because the moon is always the same distance away.”

NASA astronaut Edwin “Buzz” Aldrin salutes the U.S. flag he and astronaut Neil Armstrong put on the Moon on July 20, 1969, during the historic Apollo 11 mission.

On the other hand, Mars takes six months to reach, and you’d have to wait about a year until Mars is close enough again for the return trip to only take six months.

“You can’t make mistakes on a trip to Mars,” she said. “But on the moon you can make mistakes and come home. So, the moon’s a good place to learn.”

Choosing Which Member to Kill

Some small-scale tests of closed-loop ecosystems and habitats have been conducted on earth, like the Biosphere 2 project of the 1990s. But that ended with its eight residents starving and running out of air. When problems like those arose, they could still receive help from outside or have more oxygen pumped in. On another planet — not so much.

This 1991 picture shows the Biosphere 2 complex in the desert near Oracle, Ariz. Eight people agreed to spend two years sealed inside the 3-acre terrarium in the Sonoran Desert.
John Miller/AP
This 1991 picture shows the Biosphere 2 complex in the desert near Oracle, Ariz. Eight people agreed to spend two years sealed inside the 3-acre terrarium in the Sonoran Desert.

“If something like that happened on Mars — you didn’t have your equations figured out and it turned you weren’t making enough oxygen — you’d have to choose which member you were going to kill or something,” Kelly said. “So, we need to figure out this stuff before we get out there if we’re going to be trying to stay there long term.”

Purported Benefits

With all those risks and dangers, settling another planet must really be worth it, right? Right?

One purported, often-cited benefit is creating a sort of lifeboat — a backup planet for the human race in case this one becomes uninhabitable. But Zach argues the earth might always be the better option.

The surface of Mars as photographed by NASA's Perseverance rover in 2021

“We’re not sure there’s anything you could do to earth that would make it as bad as Mars is,” he said. “On Mars there’s no air. The soil is made of poison and toxins. There are dust storms that blot out the sun worldwide for weeks at a time. It’s bad…it is not a refuge. It probably never will be.”

Wet Blankets

So, how has the space community reacted to the Weinersmiths’ conclusions? The couple says they’ve gotten plenty of positive reactions from space professionals who’ve appreciated the realities of space colonization being spelled out publicly. Others, meanwhile, have pointed out things they missed.

Kelly Weinersmith admits they might be “wet blankets” but adds they’re huge fans of space exploration and want to see it succeed.

“I would love to see us settle space eventually,” she said. “I just don’t want us to rush into it. And so, I don’t know, we’ll just have to wait and see what happens.”

Michael Hagerty

Michael Hagerty

Senior Producer, Houston Matters

Michael Hagerty is the senior producer for Houston Matters. He's spent more than 20 years in public radio and television and dabbled in minor league baseball, spending four seasons as the public address announcer for the Reno Aces, the Triple-A affiliate of the Arizona Diamondbacks.

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