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Stephen Petranek: How Will Humans Live On Mars?

Dec 21, 2018

Part 2 of the TED Radio Hour episode The Next Frontier.

About Stephen Petranek's TED Talk

Stephen Petranek says, in the next decade, we will send humans to colonize Mars. He lays out the technology--from water-extraction to bricks made of Martian soil--that'll make life possible there.

About Stephen Petranek

Stephen Petranek is a science writer and technologist. He is the author of How We'll Live on Mars, and editor-in-chief of the technology newsletter Breakthrough Technology Alert.

Over the course of his 40-year publishing career, he's been editor-in-chief of Discover, senior science editor at Life Magazine, editor of The Washington Post Magazine, and founding editor and editor-in-chief of This Old House.

Petranek is also the co-founder and president of Arc Programs, an organization seeking to bring together health, IT, and biomedicine.

Copyright 2018 NPR. To see more, visit


It's the TED Radio Hour from NPR. I'm Guy Raz. And on the show today, ideas about The Next Frontier. And you may think that, right now, sending a handful of astronauts to Mars would be a major milestone. But what about sending a hundred people to Mars to, you know, start a colony? Could we actually do that one day?


RAZ: But we're talking, like - like, hundreds of years in the future, right?

PETRANEK: We're talking a decade to 15 years from now, at the most.


RAZ: This is science writer Stephen Petranek. And even though it might sound like science fiction, Stephen says it will happen, whether through NASA or SpaceX or some other group, humans will colonize Mars.

PETRANEK: We've had all the technology we need - the machines that can make oxygen for us to breathe on Mars, the habitats that we need on Mars. We've developed all this stuff 30, 40 years ago. We've had this technology for decades.

RAZ: Stephen Petranek has all of this mapped out. In fact, he's written a book about it called, "How We'll Live On Mars." And he picks up the idea from the TED stage.


PETRANEK: Strap yourselves in. We're going to Mars - not just a few astronauts. Thousands of people are going to colonize Mars, and I am telling you that they're going to do this soon. Some of you will end up working on projects on Mars, and I guarantee that some of your children will end up living there. That probably sounds preposterous. So let me tell you about the extraordinary adventure we're about to undertake. Mars is not our sister planet.

RAZ: And that extraordinary adventure Stephen describes? It starts with traveling 250 million miles to Mars, which means living in a spacecraft for eight months.

PETRANEK: One of the most important things about sending people to Mars is making the trip getting there pleasant and fun. The accommodations will be extremely pleasant, far more pleasant than the most luxurious first-class accommodations in any aircraft in the world. There will be much more space than you think. There will be common meeting areas. People will have meals together.

RAZ: Wow. So you've got this great first-class accommodation and great food. And, by the way, like, where's the water going to - like, water's super heavy. How do you carry all that delicious food up?

PETRANEK: Water is super heavy, and you want to get the water down to a minimum. So, for example, all the food will be freeze-dried and reconstructed with water aboard. But all the water in that spacecraft will be recycled. The water that humans use doesn't disappear. Part of it goes into their body, and the rest of it is expelled. And the part that is expelled will be reconditioned and reused.

RAZ: So you're talking about, like, you know, bottled water of pee?

PETRANEK: Correct.


PETRANEK: That happens now on the space station, for example, on the International Space Station. That happens in submarines. That happens in lots of different environments.

RAZ: So what happens when we - when we land? Like, where would we go? Where would we live? What would we eat?

PETRANEK: We will send everything we need for the first few years of life on Mars to Mars, before the first humans get there. Then we will use robots to assemble habitats, to unpack the cargo shipments that we've sent, to create some kind of living quarters that we can move out of the spaceship into.

RAZ: OK. So I get it. So you're going to sort of pre-launch the - it's like doing the Appalachian Trail, right? You, like, send packages to yourself ahead of time?

PETRANEK: Correct.

RAZ: All right. So we're there with, like, a hundred other people. And we're like, OK, here we are. We're on Mars. And food eventually is going to run out. Like, we've got a - I mean, a clock starts ticking once we land there because, yeah, we've sent some shipments of food and stuff, but I mean - right? We've got to start growing stuff. What happens?

PETRANEK: To live on Earth, you need food, water, shelter and clothing. To live on Mars, you need food, water, shelter, clothing and something to breathe.


PETRANEK: So let's look at the most important thing on this list first. Water is the basis of all life as we know it. And if you look at Mars, it looks really dry. It looks like the entire planet is a desert. But it turns out that it's not. A number of orbiters that we still have flying around Mars have shown us that lots of craters on Mars have a sheet of water ice in them.

So there's plenty of water there, but most of it's ice, and it turns out the Mars atmosphere is often 100 percent humid. This is a device hooked up at the University of Washington back in 1998. This device can extract all the water that humans will need, simply from the atmosphere on Mars. Next, we have to worry about what we will breathe. This is a scientist at MIT named Michael Hecht, and he's developed this machine, MOXIE. I love this thing.

It's a reverse fuel cell, essentially, that sucks in the Martian atmosphere and pumps out oxygen. And it will be able to produce enough oxygen to keep one person alive indefinitely. But the secret to this is that this thing was designed from the get-go to be scalable by a factor of 100. Next, what will we eat? Well, we'll use hydroponics to grow food, but we're not going to be able to grow more than 15 to 20 percent of our food there, at least not until we actually have the probability and the capability of planting crops.

In the meantime, most of our food will arrive from Earth. And it will be dried. And then we need some shelter. There is too much solar radiation and too much radiation from cosmic rays, so we really have to go underground. Now, it turns out that the soil on Mars, by and large, is perfect for making bricks. And NASA's figured this one out, too. They're going to throw some polymer plastic into the bricks, shove them in a microwave oven and then you will be able to build buildings with really thick walls.

And finally, there's clothing. On Earth, we have miles of atmosphere piled up on us, which creates 15 pounds of pressure on our bodies at all times. And we're constantly pushing out against that. On Mars, there's hardly any atmospheric pressure. So Dava Newman, a scientist at MIT, has created this sleek spacesuit that would keep us together, block radiation and keep us warm. So let's think about this for a minute - food, shelter, clothing, water, oxygen. We can do this.


RAZ: I don't know about this - radiation, living underground, freeze-dried food. Like, we might have some hydroponics, but it's a really harsh environment. So would you go? Like, would you want to live in those conditions?

PETRANEK: I would. I wouldn't go on the first trip. I think the early trips are going to be extremely dangerous. But I would like to die on Mars, just, preferably, not on impact. I think it would be the greatest adventure of a lifetime.

RAZ: Yeah.

PETRANEK: I think what happens with Mars is we build a civilization of maybe a million people within the first hundred years, and we start to terraform the planet.

RAZ: And when you say terraform, you mean, like, basically, to reengineer Mars to make it - like, the climate and the atmosphere more like Earth.

PETRANEK: Correct.


PETRANEK: That sounds like a lot of hubris. But the truth is that the technology to do everything I'm about to tell you already exists. First, we've got to warm it up. Mars is incredibly cold because it has a very thin atmosphere. The answer lies here at the South Pole and at the North Pole of Mars, both of which are covered with an incredible amount of frozen carbon dioxide - dry ice. If we heat it up, it sublimes directly into the atmosphere and thickens the atmosphere the same way it does on Earth. And as we know, CO2 is an incredibly potent greenhouse gas. It actually won't take long for the temperature on Mars to start rising, probably less than 20 years.

Right now on a perfect day, temperatures can actually reach 70 degrees. But then they go down to -100 at night. What we're shooting for is a runaway greenhouse effect - enough temperature rise to see a lot of that ice on Mars, especially the ice in the ground, melt. As the atmosphere gets thicker, everything gets better. We get more protection from radiation. More atmosphere makes the planet warmer. So we get running water, and that makes crops possible. It will rain and it will snow on Mars. Eventually, Mars will be made to feel a lot like British Columbia.

RAZ: (Laughter) I mean, I get - even though the technology exists, to me, and to, I think, a lot of people listening, this sounds outlandish.


RAZ: But you are convinced this is going to happen, that humans will do this.

PETRANEK: One of the reasons that I wrote the TED book "How We'll Live On Mars" is that I wanted to tell people that this is a completely unregulated environment. People are going to Mars. Whether we like it or not, SpaceX is devoted to getting to Mars. There's going to be a space race to Mars. People are going to Mars. There's going to be a civilization on Mars. It's going to happen a lot sooner than people think. The only reason that I'm trying to point all this stuff out is that now is the time to think about this.

RAZ: Let me just push back on something for a second here because a lot of people, like astronomers and scientists, they're saying, we should not be focused on looking to Mars as a backup planet, right? - that instead, we should be focused on fixing Earth. Like, this is our planet. We - and we're destroying it.

PETRANEK: I'm sympathetic with the idea of leaving Mars alone for scientific exploration and not for massive human habitation because Mars is an extraordinary scientific park, just as we've treated Antarctica as a scientific park. But we need to get realistic here.


PETRANEK: Homosapiens arose in Africa 2 million years ago. It wasn't till about 60,000 years ago that they began to leave Africa en masse. And they move beyond the next horizon. And they move beyond the next horizon. And they eventually populated the entire Earth. They learned along the way that that is a survival technique. Humans have been a nomadic species for 99 percent of their existence. It's only in the last 20,000 years that we've actually built towns, had sustainable agriculture and created a food supply that would allow us to stay in one place. That's a very recent development.

I think that, actually, exploration is built into our DNA. And I think it's important that it's built into our DNA because if the human species is to survive, it must become an interplanetary species. And I'm not just talking about Mars. You have to go well beyond Mars. I think by then, we've found other habitable, Earth-like planets, where we don't have to terraform them, that we can actually reach in a human lifespan.

And then we begin to move off of Mars and beyond Mars in this nomadic way to other planets. And that - it, like, hurts your Earth-first kind of sensibilities to say, oh, we're just a species that keeps moving on and using up resources. But the truth is that those resources that we're using up are expendable. You know, eventually, the sun begins to expand and completely destroys the Earth.

RAZ: Yeah, we get a couple hundred million years before that happens. I mean, you know, call me an Earth-firster (ph) - guilty - but, I mean, you know, like, this is - kind of makes sense that we're here to stay for a while until - well, until, you know, until we go. But I think we still have some time.

PETRANEK: Well, first of, all humans are not going to move to Mars as the preferable place to be. There's going to be just a few million people. The vast majority of people are going to continue to live on Earth, but you do need a backup planet.


PETRANEK: Ask any 10-year-old girl if she wants to go to Mars. Children who are now in elementary school are going to choose to live there. Think for a moment what we had when John F. Kennedy told us we would put a human on the moon.


JOHN F KENNEDY: Like, why, some say, the moon? Why choose this as our goal? And they may well ask, why climb the highest mountain?


PETRANEK: He excited an entire generation to dream.


KENNEDY: We choose to go to the moon. We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard...


PETRANEK: Remember when we landed humans on the moon? When that happened, people looked at each other and said, if we can do this, we can do anything. Think how inspired we will be to see a landing on Mars. What are they going to think when we actually form a colony on Mars? Most importantly, it will make us a spacefaring species. And that means humans will survive no matter what happens on Earth. We will never be the last of our kind. Thank you.

RAZ: That's Stephen Petranek. He's the author of the book "How We'll Live On Mars." You can see his full talk at

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.