IRA FLATOW: This is Science Friday. I’m Ira Flatow.

The next ambitious goal for space flight is to send a human to Mars. Now, of course you know that yearning for Mars is nothing new. We’ve been talking about inhabiting Mars ever since astronomers thought they saw canals on the red planet. But something has materially changed. After decades of sending space probes and rovers, there are actual plans to put people on Mars. But there’s one small detail that needs to be worked out if we are to land and even colonize that real estate– how to first survive the trip, and then inhabit a world hostile to humans. As for worlds beyond Mars, well, it could take years or even generations to get there. How do we accomplish that?

My next guest says the biggest technical challenges could be met by engineering humans, ourselves, to survive long-term space living. And he’s come up with an extensive plan for that in his new book, called The Next 500 Years– Engineering Life to Reach New Worlds. Christopher Mason is here to fill us in on that plan. He’s also professor of physiology and biophysics at Weill Cornell Medicine in New York. Welcome to Science Friday.

CHRISTOPHER MASON: It’s a pleasure to be here. Thanks for having me.

IRA FLATOW: So nice to have you. You say that humans have a responsibility to preserve life. In other words, a duty to engineer. What do you mean by this? Why do we have a duty to do that?

CHRISTOPHER MASON: So I just published this book because I really wanted to give a concrete plan, as well as a sense of a reason as to why we should go. A lot of times, people think of exploring space or going to other faraway islands just because. Because it’s there, because it’s hard, all of which are good reasons, and humans have always been extraordinary explorers. But I make the case here that really it’s a moral argument, in which you say– if you’re at a party and you say, I want to talk to you about duty, most people immediately would go get a drink and talk to somebody else.

But in this case, I make the strong argument because we’re the only species with awareness of extinction, and I think, therefore, we have an actual duty to prevent it. Not only our own, of course, but also to serve as guardians and shepherds really for all the lifeforms we see on Earth. So we have this unique capacity and, therefore, this unique duty that I think extends out to the stars.

IRA FLATOW: And in your book, you outline a 500-year plan for reengineering. How do you approach this from the very start?

CHRISTOPHER MASON: So I put this together first as a series of bullet points on a bar napkin, which is where a lot of good ideas start. But again, it’s another human very specific trait that we can make plans that are intergenerational, that we can look far ahead. And posted this on the lab’s website in 2011, and started to realize that we really need to have a better understanding of genetics, and also think about how it changes in the most stressful of environments.

And that was actually when I first started writing– the first grant proposal I wrote for the lab was one to NASA saying we should start to look at this for astronauts. And at the time, there had never been something quite like this study until we did something with the Kelly brothers and the twin study. So I wanted to lay out a 10-phase plan to better understand the human genome in the most stressful of environments, and then also to think about what could be modified at the DNA, the RNA level, even microbes, think about what are things that could be slightly tweaked to give us better odds for the long missions ahead.

IRA FLATOW: Slightly tweaked and stressful environments, I mean, there’s no better place to start than radiation, because it’s one of the biggest risks to the human body in terms of long-term space flight. Tell us, what could we do genetically to protect ourselves from the effects of radiation?

CHRISTOPHER MASON: So we have a number of things that are already done, both physically and pharmacologically, just to keep everyone safe. And this is done not just in space, but also in the clinic, thinking about when you have radiotherapy. How do you actually keep all the cells safe that aren’t the ones being targeted? So think about this when you get x-rays at the dentist. We do the same thing there. It’s just simple protection.

But we know there’s actually microbes that can make small molecules that can keep intestinal lining safe. One molecule is called arachidonic acid, and we can actually think about what do we give that could actually help be protective. Or we’ve even looked at things from other species that could keep us safe. One little organism is called a water bear or a tardigrade that can survive the vacuum of space.

And in our own lab, we’ve had human cells that can survive really high amounts of radiation, but still be fine. But we’re basically borrowing the evolutionary tools and tricks of a different species to keep ourselves and our own cells safe, at least in culture. We’re not doing this in astronauts yet. That’s probably several decades away. But the concepts and the molecules and the tools we’re beginning to develop now, and we can see them work extraordinarily well in my laboratory today.

IRA FLATOW: You know, you’re familiar with the physicist Freeman Dyson, the late Freeman Dyson. He had some far-fetched sounding ideas that they used to call Dysonian because they were so farfetched. Do we have Masonic things that we’ll have to rebrand? I mean, your ideas are far-fetched, but they’re really based in real science. And I’m talking in specifics about using chloroplasts to create chlorohumans. I think humans with green skin that photosynthesize?

CHRISTOPHER MASON: Yeah, so I have a whole section of the book that describes what could happen if you’re really far from the sun. Every photon is a little bit of energy you’d want to capture. And everything that’s written in the book is projected, it’s prospective, but it’s all based on experiments we have working in the lab today or molecules we’ve already found.

And there are other creatures that sometimes eat chloroplasts and can survive with them for a little while, so I talk a bit about that in the book. But I also did a fun calculation to say, if you really did have green skin and wanted to be a chlorohuman, how much skin would you need, and you wanted to lay out in the sun, say, today on Earth?

It turns out, if you do the math, and you make some assumptions and the formulas in the book, you just need about two tennis courts’ worth of skin, which is kind of a fun idea to think about. Some people think it’s totally disgusting. I think it depends on your view of skin. But at least we have some of the math in terms of what we need for shuttling photons to capture them in terms of laying inside of a human cell, which, again, sounds a little bit kooky until you realize that mitochondria, which are the powerhouse of our own cells, are themselves probably captured bacteria from many, many millions of years ago. So we already kind of have some visitors in our human cells that have been with us for a long time.

IRA FLATOW: Do you think that we have to genetically engineer astronauts for specific planets? Let’s say if you’re going to go to Saturn, or Saturn’s moon Titan, you have to have different kinds of genetic modifications for going to Mars.

CHRISTOPHER MASON: It’s possible. And I really want to think carefully about, anytime you modify someone, there’s two kinds of modifications. And a lot of people talked about this with the CRISPR revolution that’s happened recently, is that you can modify someone somatically, meaning just their current cells, or germline engineering, where germline means you’re actually changing multiple generations, and you’re constantly changing the human genome really forever.

Now, the first one is actually widely deployed. There’s already hundreds of millions of dollars at the NIH that’s funding clinical trials today for sickle cell anemia, beta thalassemia, other diseases. And the success stories are astounding. We actually can already see really great evidence of curing disease by doing gene editing today in humans that’s really successful.

But none of them are doing germline engineering, where you do it basically as a way to change the next generation, because it’s still too early. We just don’t know quite well enough how well CRISPR works to make sure there’s no off-target effects, or at least an acceptably low number. So that’s why I say some of these ideas will be decades away.

However, if you think of really harsh planets, sometimes the changes would make it so you could only survive on one planet, if they’re too significant. But I think that would be a failure. I describe in the concept of the book something called planetary liberty is how many planets can you live on if you’ve done your engineering correctly.

So would you be able to go to Mars with 38% gravity and come back and still be fine. Today, that’s hard to do. And Captain Kelly described it quite clearly when he came back to Earth after a year in zero gravity. It was hard.

But what if you did 38% gravity for one or two years and come back? Would that be one third as hard, or half as hard, or twice as hard? We just don’t know yet. But I would want to endeavor to give the greatest degree of planetary and cellular liberty to anybody.

IRA FLATOW: Well, speaking of Captain Kelly, he’s sitting right by, standing by to come on the program. Scott Kelly is joining us. He’s a former NASA astronaut who spent an entire year up in space. He’s author of many books, including Endurance– A Year in Space, a Lifetime of Discovery. Welcome to Science Friday.

SCOTT KELLY: Thank you for having me, Ira.

IRA FLATOW: Do you think that there are enough astronauts who would love to take on this kind of challenge?

SCOTT KELLY: Well, if you’re talking about going to Mars, I think most of them probably would do it. The way I feel about it is I would go in a second, as long as I had some kind of reasonable possibility of coming home. I’m not a fan of the idea of just moving to Mars with no hope of ever returning, having lived in a confined environment for a long period of time in essentially something that would be similar to a Martian habitat. But flying around the Earth in low Earth orbit, I would not want to spend the rest of my life like that. But I would certainly go if I had the opportunity. So if NASA is listening, you know where to find me.

IRA FLATOW: Well, let me see if I can make a meeting, a mind meld here. Scott, would you be willing to get genetically tweaked if it meant increasing your odds of surviving a trip to Mars?

SCOTT KELLY: Absolutely. I was all about stretching the limits of the science. I mean, I even offered up to put a pressure sensor in my skull to better understand this issue we have with vision in astronauts and swelling of the optic nerve that they think is probably caused by fluid shift to the brain in the absence– or living in microgravity.

So I considered it part of my job, and I was basically all in on the science program, even if it involved some stuff that was kind of out there, cutting-edge, new ways to prevent the nasty things that happen to us when we’re flying in space.

IRA FLATOW: Christopher, let’s say that Scott volunteers to be part of the astronaut corps that will accept genetic engineering. How do you get that past an ethics panel about what you’d like to do?

CHRISTOPHER MASON: Yeah, I actually think it’s relatively easy in the sense that we– like with any medical therapy, with any medical treatment, we define what we know to be the risks, and make sure that the risks we’re proposing aren’t worse than what alternative would be. And then it also has to be necessary, something that’s not just whimsical. We’re not just wantonly editing humans because we’re curious, although we do that with human cells in a dish.

But we’d have to be clear that this is a benefit, and that we can track outcomes and ensure it’s safe and efficacious. And we would start small. It’s like with most clinical trials, like recently with vaccine trials we’ve all seen, you do phase one, two, and three. You start small. You get bigger and test safety and efficacy.

But the problem with astronauts is there’s only, I think, to date, 590 or so ever. And so we can’t run 10,000 person clinical trials like these. But what we can do is take lessons from other therapies that are already ongoing that are using somatic methods to repair diseased genes, to modify– to even turn genes back on that were once turned off.

What’s called fetal hemoglobin, you can actually– we all had a different version of hemoglobin, which carries oxygen in our blood, that was active when you were a fetus. And for some therapies, they’re just turning it back on. It’s actually being deployed right now in clinical trials. So I think we would, for the astronauts, we’d learn from them, as well as every other variation of genome modification therapy.

IRA FLATOW: Christopher, you looked at the genetic changes happening in Scott during his trip. There was some pronounced ones. One example is that his telomeres changed.

CHRISTOPHER MASON: There are some claims that he got a little bit younger in space. By multiple measures, actually. His telomeres got longer. I think last time on the show, we also heard Dr. Bailey talking about that. And really, other measures, even some of the mutations he saw that were in him before he went into space got better, even. So there were some aspects of flight that were good. He lost weight, he got taller, and got a little bit younger, in some ways, by telomeres, which sounds like the best diet plan ever, really, to get taller, younger, and lose weight.

But a lot of it did go back to normal when he got back to Earth. And so I can confirm here once and for all that Scott has a very great genome. It’s really a solid piece of DNA.

IRA FLATOW: This is Science Friday from WNYC Studios. And for you, Scott, getting back to Earth, once you got here was not– well, how should I put this– a terribly pleasant experience.

SCOTT KELLY: Yeah, it was a little rough, initially. And I think everyone deals with returning to Earth, or even going to space, differently. Some people get sick when they get there, others don’t. Some people have issues when they return.

My flights were progressively longer. I flew into space four times. My first flight was a week, my second two weeks, my third 159 days, and the fourth leg being nearly a year, at 340 days. And it seems to me that the longer I spent in space, my symptoms were progressively worse. If you actually graphed that time in space over my four flights, it’s a second order polynomial.

So if I was going to fly in space for a fifth flight, it would have to be like– to match that curve, it’d be like 500 and something days. Or five years, I’m sorry. It would be like five years in space. So that’s why my next flight has to be to Mars because that’s where the curve projected it to be.

But yeah, every time I flew, the symptoms were progressively harder on me. And I would say the first few days back were pretty tough, as I explained in the beginning of my book, when I returned and wrote that.

So the other thing that Chris did not mention, though, is that not only was I taller, thinner, better telomeres, but according to Einstein’s general relativity, I was actually three milliseconds more younger than I used to be from my twin brother, Mark, because I went so fast for so long.

IRA FLATOW: There goes those birthdays. Wow. Everything in space travel or in large planning has an order. You have a plan. Let’s say that you get enough funding. You know, I’ll give you the Science Friday blank check right here in my back pocket. Too bad we’re not in this– I’m not going to Venmo it either because it’s not there.

What would you do? I mean, what steps do you take to create the reality that you see, Christopher?

CHRISTOPHER MASON: Something that we’re doing already, which is more health monitoring for astronauts– and NASA is doing a lot of this already– is longitudinal whole lifetime monitoring of astronauts to make sure we keep them safe, and see if there’s any changes we missed during the missions.

But what’s really exciting, I think, is we’re now looking at other commercial spaceflight providers. A lot of them are going planning to go to the moon, going farther. And so I think that’s happening. A lot of the work in the lab is building these genetic circuits and these constructs to actually make sure that they work in human cells, and can be really protective.

So some of this is already happening but I think the other thing is to really think also just about activating– so I could talk about some of the genes that are inactive, or adding in components that we can make ourselves more self-reliant. The essential amino acids that we all have to eat because we can’t make them, I feel like we should add them back in. So a lot of this is experiments we’re just starting now.

But then also some of the CRISPR therapies being tried in humans today, some of the genome editing, it’s happening today. So I think we need to do more of it, and scale it up. I don’t think we have to– what’s great is we don’t have to invent some entire new kind of science, we just have to do more of it and do it faster.

IRA FLATOW: And last question to you, Captain Kelly. Let’s say you could go anyplace. Think about it. Where would you like to go?

SCOTT KELLY: I would go to the nearest Earth-like planet, which is really, really far away. I mean, not in our solar system.

CHRISTOPHER MASON: To Scott’s point, Mars actually, as far as a planet to go to, it’s one of the crappier planets. It’s just it’s nice because it’s close, but if you’re looking for one– planets that we know of that have a good size and have likely liquid water and are probably the right temperature, there’s a lot better candidates that are really close by, relatively close by in galactic terms, yeah.

IRA FLATOW: Unfortunately, we are out of time. I would like to thank my guests, former astronaut Scott Kelly, out with a new book, Goodnight, Astronaut, and Christopher Mason, professor of physiology and biophysics at Weill Cornell Medicine. And his new book is the next 500 Years– Engineering Life to Reach New Worlds.

CHRISTOPHER MASON: Thanks so much. It was a pleasure.

SCOTT KELLY: Yeah, thanks, Ira.

IRA FLATOW: And if you want to hear more about Scott Kelly’s time in space and read an excerpt of Christopher’s book, go to our website. It’s up there at sciencefriday.com/newworlds. After the break, as you’ve been hearing, technology changes over time, and so do our concepts of what’s right and wrong. Are they connected? My next guest says yes. Stay with us.

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