The End Of Astronauts: Why Robots Are The Future Of Exploration

25:41 minutes

two astronauts in space repairing the hubble space telescope, behind them. the telescope is far larger than they are. one of the astronauts wave at the camera
Two astronauts repairing the Hubble Space Telescope in 2009. Credit: NASA

Sending astronauts into space is arguably one of society’s most impressive scientific achievements. It’s a marvel of engineering, and it also taps into the human desire for exploration. 

But just because we can send humans into space, should we? Robots are already good space explorers. And they’re only going to get smarter in the near future. 

Martin Rees, the United Kingdom’s Astronomer Royal, and Donald Goldsmith, astrophysicist and science writer, argue that the cost of human space travel largely outweighs its benefits. They talk with Ira about their new book, The End of Astronauts: Why Robots Are the Future of Exploration.

We asked you if you think space exploration still has a place for humans—or if robots should lead those activities.

“It’s not a question of ‘should,’ it’s a question of ‘is.’ Robots return much more science for every dollar invested. They don’t need complex and heavy life-support systems or protection from harsh environments. They can be optimized for specific missions in ways humans can’t be.”
– Pace A., via Facebook

“Yes, much cheaper to explore without maintaining the adaptation to extreme environments needed for humans.”
– Rich W., via Facebook

“Yes. Robotics can do so much for do little. Send a thousand robots to explore all reaches of our solar system and we will see and learn so much for less cost and no risk to human lives.”
– Chuck M., via Facebook

“Humans should go when it makes sense. But most missions should be robots, because it’s cheaper and that means you can send more missions and many more missions for the same cost.”
– Mark C., via Facebook

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Segment Guests

Martin Rees
Donald Goldsmith

Donald Goldsmith is a science writer and astrophysicist, and the co-author of The End of Astronauts: Why Robots Are the Future of Exploration.

Segment Transcript

IRA FLATOW: Sending astronauts into space is arguably one of the most impressive scientific human achievements. Not only is it a marvel of engineering, but it plays into the human desire for exploration. But just because we can send humans into space, should we? Robots are already good space explorers, and they’re only going to get smarter in the future.

My next guests argue that the costs of human space travel far outweigh its benefits. Dr. Martin Rees is the United Kingdom’s Astronomer Royal and one of the world’s most respected and visible cosmologists. And Dr. Donald Goldsmith is an astrophysicist and science writer. And together, they have written the book The End of Astronauts– Why Robots Are the Future of Exploration. Martin, Donald, welcome to Science Friday.

MARTIN REES: Good to be with you.


IRA FLATOW: OK, let’s talk about it. Martin you’ve been one of the UK’s most public faces of science for decades. And you are certainly aware of the tug of war, the debate among astronomers about whether robots or people do a better job at space exploration. So why a book right now to bring that all up again?

MARTIN REES: Well, let me say first that Don and I are both old enough to remember Neil Armstrong’s one small step. And it was a heroic episode. And I think we both suspected that, since it was only 12 years from the first Sputnik to feet on the moon, that maybe within 10 or 20 years more, we’d have had footprints on Mars. But of course, as we know, 50 years later, the Apollo program is still the high point of human spaceflight.

And that’s really for two reasons. The first reason is that, of course, it was hugely expensive, and it was funded by the Americans as an exercise in superpower rivalry to beat the Russians. And it wasn’t worth continuing that having beaten them in this particular competition.

But also, the other reason, and this is closer to what our book’s about, as robots have got better, then the case for sending humans, the need for humans in space, is far less, either for exploration or for assembling structures and things like that. And so our main point is that, given that it’s usually more expensive to send humans, especially on a long voyage to Mars, then the public shouldn’t support this expense.

IRA FLATOW: Don, can you lay out the basic arguments about why it’s so much more expensive to send humans?

DONALD GOLDSMITH: Well, it’s because we’re such fragile, sensitive creatures who insist on eating and breathing and so forth, and also on coming back. In short, a robot goes out into space and spends six months on the way to Mars very happily consuming almost nothing. Think what you have to do for a human on that voyage.

So there’s also the protection issue. Not just the regular holding the air in, but also, there are solar storms that could kill an astronaut with radiation should they occur. And you have to, at least if you’re being kind to these astronauts, have a structure where they can have a special way to stay safe during the face of a solar storm. All in all, it’s really kind of simple. You’re asking, why is it easier to send a letter than to send a person across the country?

IRA FLATOW: And that goes not only for going to Mars, but for near-Earth orbit? Is that not correct?

DONALD GOLDSMITH: Near-Earth orbit, of course, is much more expensive. But remember that the moon is roughly a quarter of a million miles away. The journey to Mars is hundreds of millions of miles. You think of it as a thousand-times factor.

So it’s a lot more. But as you know, certain people are now willing to pay these huge expenses. We could talk about pollution and even more space crowding. Near-Earth orbit is getting very full. Someday, there will be collisions, if not with human vehicles, then among the myriad satellites we keep putting up there.

IRA FLATOW: And the International Space Station, Martin, cost a lot of money, right, compared to what it would have been to just have robots going around the Earth.

MARTIN REES: It did indeed. It cost a 12-figure sum if you add in the cost of the shuttle. And also, it wasn’t all that inspiring. I mean, it made the newspapers when the toilet didn’t work or when Hadfield, the Canadian astronaut, sang David Bowie songs and played his guitar. But the only worthwhile research was the effects of zero-gravity on human beings for a long time. So that’s all it did. And it was hugely expensive.

IRA FLATOW: I’m talking with Martin Rees and Donald Goldsmith about their book The End of Astronauts– Why Robots Are the Future of Exploration. This is Science Friday from WNYC Studios.

So Martin, is it your mission, then, to talk NASA, SpaceX, Blue Origin out of sending humans into space?

MARTIN REES: Well, to talk NASA out of it, because that’s public money. The other reason why we don’t need humans is that AI is getting better. At the moment, if we send a probe to Mars, it’s not able to decide where to dig, where’s an interesting sample. But in 10 or 20 years, the kind of AI that allows machines to look at 100,000 X-rays of your lungs and decide better than a human whether you’ve got lung cancer– that sort of technology will enable the AI to do the geology. You don’t need the people for that. So I don’t really think there’s any case for NASA or any public body sending people into space.

But on the other hand, I think they’re– I am inclined to cheer on the private ventures for two reasons. First, they can take higher risks. You probably remember that the shuttle failed twice in 135 launches. And each of those failures was a big national trauma, because they’d presented it as safe, and they’d launched a woman schoolteacher and all that.

But a 2% failure rate is acceptable to lots of adventurers. And that, therefore, means that a private exploit by SpaceX or Blue Origin can accept higher risks and launch people who are prepared to take those risks, and maybe even on a one-way trip to Mars. Elon Musk has said he wants to die on Mars, but not on impact. And he’s now about 50, I think, so 40 years from now, he may be able to do it. And what a way to go.

IRA FLATOW: But there was a survey, if I remember correctly, a poll of people when the news came out that people were talking about that Mars would be a one-way trip– what, there were tens of thousands of people who signed up for that.

MARTIN REES: I think there will be people who will go to the moon at private expense, and they will accept the high risk. And I think there will be those who take a one-way trip to Mars. Think of the polar explorers 100 years ago, Captains Scott and Amundsen and Shackleton. They accepted a 50% risk of not coming back, and they were completely out of touch with the rest of the world.

And so there are people with that spirit who will want to go. And I think we should cheer them on. And there may indeed be a small colony of such people by the end of the century living on Mars. But what there won’t be, I hope, is mass emigration. And here I strongly disagree with Elon Musk and my late colleague Stephen Hawking, who talked about the idea of escaping Earth’s problems by going to Mars.

IRA FLATOW: Why don’t you think there will be mass emigration to Mars?

MARTIN REES: Well, first of all, living on Mars is less comfortable than being at the South Pole or at the bottom of the ocean or the top of Everest, so it’s not a comfortable place to go. But also, it would be hugely expensive. And also, it’s a dangerous delusion to think we can escape the Earth’s problems by going to Mars, because it’s true, it’s hard to deal with climate change and all these problems of the Earth. But that’s a doddle compared to making Mars’s atmosphere breathable and terraforming Mars.

So I think space exploration is for adventurers. It shouldn’t be called space tourism. It’ll never be routine. It should be called space adventure. But we should cheer on brave people who do it.

IRA FLATOW: That’s Martin Rees, the United Kingdom’s Astronomer Royal, who along with Donald Goldsmith has written a new book, The End of Astronauts– Why Robots Are the Future of Exploration. We have to take a break. And when we come back, we’ll talk more about space exploration, including some of the places the authors would love to explore with robots. We’ll be right back after this break.

This is Science Friday. I’m Ira Flatow. Case you’re just joining us, I’m continuing my conversation with Martin Rees and Donald Goldsmith about the future of space exploration and their argument against sending more astronauts into space. And their case goes beyond the cost. Martin Rees, the United Kingdom’s Astronomer Royal, says there could be some long-term unintended consequences of, say, the human habitation of Mars.

MARTIN REES: If we look to the 22nd century and beyond, if there are some people on Mars, privately funded, then they will find themselves ill adapted to life there, obviously, because we’ve evolved through Darwinian selection to be suited to the Earth. But they will then, 50 years from now, have all the technology of genetic modification and cyborg, et cetera, to adapt themselves. And those techniques, we hope, will be regulated here on Earth, but they’ll be away from the regulators. And so if there was a colony of people out there, then they might, within a few centuries, evolve into a different species, whether flesh and blood or electronic, because they would have the technology, freedom from regulation, and they would adapt themselves to living on Mars and perhaps going off into the blue yonder.

IRA FLATOW: You’re talking about genetic engineering-wise? They would genetically engineer their bodies to become more adaptive?

MARTIN REES: Well, they would or their progeny, to be more adaptive. And that technology, I think, will be available by the end of the century. And here on Earth, we have less motive for using it. And I think we’d want to regulate it on prudential and ethical grounds.

But these pioneers on Mars would be away from the regulators. And they’d have the motive, so I think a feasible scenario is that that community on Mars will eventually develop into a rather different species. And if it’s a development into an electronic species, which is what some people like Ray Kurzweil expects as the future of humanity, then, of course, they’d be near immortal. And then they may not want to stay on a planet at all. They may prefer zero gravity. And they may embark on interstellar voyages.

So that’s the scenario for the far future. But what we’re talking about in our book is the nearer term, when we don’t think that public money should be spent on sending astronauts into Earth orbit or to assemble structures in space or even on the moon.

DONALD GOLDSMITH: Not to mention, if I may chime in, mining the asteroids, which is very big in some people’s minds. Again, you don’t need– if you’re really going to do that, machines will do far better than humans. They’re already almost capable of this sort of thing.

Who claims to know what a hundred years from now, let alone a thousand, humanity will be like? Only the doomsayers, and they’re wrong, I hope. After all, in the long run, if private entrepreneurs, including those from many countries, are all going to go to the moon or Mars and do things, it’s probably not going to be any wonderful community more than the current international community is. And all sorts of problems will arise. But predicting them or even thinking they’ll happen is really not in the cards.

IRA FLATOW: On the other hand, we’ve been pretty peaceful in Antarctica, where there are treaties.

DONALD GOLDSMITH: Yes, the Antarctic Treaty is the single greatest success of the United Nations treaty organizations, as far as I can tell, where people did agree wonderfully that although everyone claimed pieces of Antarctica, and those claims overlapped, they would be totally respected. They only agreed not to do anything about it. And that so far has worked.

And it’s partly because they haven’t found uranium or easy oil deposits in Antarctica. The day it turns out to be full of cobalt or mineral wealth or something, I’m afraid that treaty is in deep, deep danger. It came to creating a treaty for the moon along similar lines, the big countries simply wouldn’t sign on, because it was saying it’s all for peaceful purposes and not for any one country’s benefit and so on.

IRA FLATOW: Let’s talk a bit about going to the moon. Last year, China and Russia announced a joint program to create the International Lunar Research Station. And of course, NASA is spearheading the Artemis mission to return to the moon. Why now is there interest in humans, do you think, Don, returning to the moon? And might that not be an interesting place to set up a human-habitated moon base?

DONALD GOLDSMITH: Certainly, if you’re going to think of habitats on other bodies in the solar system, the moon is the natural one. It’s so much closer than anywhere else, so much easier to get to, full of solid ground that we understand pretty well. So if you think that humans belong in space, and you want to learn how they handle another low-gravity object, why of course you would do the moon.

It only begs the question, what do you do there? You can walk around geologically exploring. Well, OK, that’s what robots do.

You could try to mine important things. There’s a whole thing about helium-3 for nuclear reactors, which is somewhat more abundant on the lunar surface. But just getting at it is no picnic. You learn how to build habitats out of lunar rock, and you learn how to extract even oxygen from lunar rocks. It’s a lot of work, and the initial stages would involve enormous amounts of material ferried from Earth.

I’m not saying it couldn’t happen, of course. The next question is just why should it happen if your point is only to prove that humans can live in space? It’s a circular argument.

IRA FLATOW: Martin, what about building a telescope, a radio telescope, on the other side?

MARTIN REES: Well, I would certainly say that that is a good use of the moon, because the far side of the moon is shielded from the radio interference from the Earth. And that’s a good case. But that could be assembled by robots, even present-day ones, certainly the kind that we could imagine existing in 10 or 20 years. So the main point is that we can do these things without humans much more cheaply.

IRA FLATOW: And of course, beyond Mars, you argue that exploring asteroids and the moons of Jupiter and Saturn are more scientifically interesting. I think Arthur C. Clarke picked that out first many decades ago. They’re easily– those are not places, Martin, you want to send a human, are they?

MARTIN REES: No, it will be a multi-year voyage, obviously, which would be even less feasible than sending people to Mars. But not much more difficult for a robot because, as Don said, the robots just hibernate happily on the long voyage. They don’t need food or resources. And they could just as easily explore the frozen surface of Europa, a moon of Jupiter, or Enceladus, a moon of Saturn, which are exciting places because if there was any vestige of life there, that would indeed be of huge importance.

IRA FLATOW: Which place would you go first?

MARTIN REES: I think exploration of those moons would be very exciting because, of course, one thing we’ve learned in astronomy in the last 20 years is that most of the stars are orbited by retinues of planets. There are zillions of places where life could exist. There are millions of planets which are rather like the young Earth, but we don’t know if life is there. But it could be that life is a rare accident, just happened in one place.

But the reason it would be great to go to the moons of Jupiter or Saturn is that if you found any kind of life on either of those, it would say straightaway that life couldn’t be a rare fluke that just happened once. If it seems to happen twice within one planetary system, then it must have happened in a billion places in the galaxy. So detecting any life on the moons of Jupiter or Saturn would be hugely important, because it would say the whole galaxy was teeming with life.

Now, I emphasize that because you might say, what about life on Mars? That would be exciting, too. But that wouldn’t clinch this case in the same way, because it’s possible that life could move on meteorites from Mars to the Earth. Indeed, some people say that we are all in a sense Martians and that life started on Mars and then came to Earth on a meteorite.

But if it existed as far away as Jupiter or Saturn, you couldn’t make that argument that it went from one to the other. So that would clinch the case that life was ubiquitous in the galaxy. And that’s why, if you ask me where I would send a probe, I would send it to those places.

IRA FLATOW: And any one moon in particular your favorite?

MARTIN REES: Enceladus and Europa. They’re the moons which are covered in ice. And there’s thought to be water underneath them. So there may be things swimming around there.

IRA FLATOW: Do you think if we found life in our solar system, we could handle that?

DONALD GOLDSMITH: Yes, certainly. I think people would be overjoyed, and they’d want to learn a little more about it. And then having learned it was merely microbial life, which it surely would be, they’d be utterly disappointed and said, I thought this was going to be people.


MARTIN REES: Well, of course, it wouldn’t be very exciting. But it would, as I say, indicate that the origin of life– which is of course still not understood. People know that Darwin explained how life evolved from simple beginnings. But the transition from complex chemistry to the first reproducing, metabolizing entities you’d call alive is still not understood.

It could be a rare fluke. It could be ubiquitous. And that’s why other instances elsewhere in our solar system, even if it’s boring, simple life, would still be important, because they would suggest that if there was another Earth-like planet orbiting another star, then life could very well have started there.

IRA FLATOW: I know in the book, you describe Princeton physicist Gerard O’Neill’s idea for a floating, rotating space habitat, which he developed in 1969, the idea. Well, tell me about his vision and why he wanted to create it.

DONALD GOLDSMITH: Well, although I interviewed the man once, I don’t really know his inner thoughts. He was an engineer who thought big. And he attracted followers who were those who thought, this is marvelous, we could live in space. You could simulate the Earth’s gravity. None of this evolutionary process that Martin was talking about. You can farm, and you can have all sorts of communities, each with their own thing going. This was, after all, the ’60s.

And I suspect– I always felt there was an element of it’s the people you leave behind. You also have to take into account that only the right people would go. There’s been a psychological profile. Now it’s more of a sociological study about what would really be likely to happen is the strong colonies would overshadow the weak and take over them, as has happened on Earth.

But whatever it is, it’s– by the way, it’s Jeff Bezos’s dream, too. In contrast to Musk, he wants to put billions of people in these habitats. To me, it sounds like a very sad giving up on Earth. We’ve got a wonderful planet going here. It would be nice if we could all live in a little more peace and harmony and treat it correctly.

MARTIN REES: To be fair to Bezos, I think he’s got an idea that is perhaps slightly more appealing, which is to move industry into space. And if that could be done using robots, that would be good. But again, it doesn’t need people. And the O’Neill colonies, they looked rather like a sort of Californian suburb where you were on the inside of some spinning cylinder, et cetera. But whether people will prefer to be out there rather than down here is unclear. But that’s a far future scenario, certainly not this century.

IRA FLATOW: This is Science Friday from WNYC Studios. My guests are Martin Rees and Donald Goldsmith, and we’re talking about their book, The End of Astronauts– Why Robots Are the Future of Exploration. Well, another far future scenario, Martin, is about terraforming Mars. Is that not a good idea if we really need an escape hatch?

MARTIN REES: Well, you say it’s “we.” I think it will be a post-human enterprise. But one important point is that future evolution is not going to be the slow Darwinian evolution where it takes hundreds of thousands of years for a new species to evolve. It’s going to be something that happens on a technological timescale with cyborg and genetic modification. So I think it’s not clear whether humans will evolve into creatures able to live on Mars as it is or whether the whole of Mars has to be changed so that humans as they are now have to live there.

DONALD GOLDSMITH: The best argument against terraforming Mars is the horrible job we’ve done of terraforming Earth. And if you picture these colonies, colonists on Mars, the Earth has been destroyed. We ruined it, so it’s a good thing we have an escape hatch on Mars. How are these people going to settle down, cyborg or not, and say, well, let’s just rebuild a better future? I’m afraid in my sad vision of humanity, they would bring the same personalities with them, the same problems, on a very much more limited set of resources, a very much tighter schedule to avoid catastrophe.

IRA FLATOW: Martin, I can’t let you go in the couple of minutes that we have left about getting your opinion about the image of the black hole at the center of our galaxy that was revealed last week. What are your thoughts on that?

MARTIN REES: Well, I watched the NSF press conference last week. And I have to say I was slightly underwhelmed in that I didn’t really feel that we were going to learn anything new about the black hole at the galactic center from these measurements. These measurements are a huge logistical achievement because they tie together huge data streams from seven or eight different radio telescopes around the world. But the challenge is so huge, and they didn’t really get a very sharp image much.

But I think that technique is going to have to await having at least one of the antennae up in space, and then you get a longer baseline than the diameter of the Earth. And that will be exciting. So I think we’ve got to wait for that before this particular technique can really give us a map of the immediate surroundings of a black hole.

But there are other techniques. There’s another interferometer being used on the European Southern Observatory’s array of telescopes, working in the infrared at about 2 microns. And this instrument, I think, can perhaps do a better job on our galactic center.

IRA FLATOW: When you say a better job, are you saying the image was a bit too fuzzy?

MARTIN REES: Yes. The image was fuzzy. And it was fuzzy for two reasons. First, the limited resolution, but secondly, because the situation is varying on the timescale of the observation.

The reason that it was harder to observe our galactic center than the bigger black hole in M87 is M87 didn’t change very much on the timescale of 10 minutes, whereas the galactic center probably did. So things were blurred because they were measuring something which was moving during the time of their exposure, as it were. And so a technique which can get better time resolution is needed if we want to observe the galactic center, because it’s intrinsically changing on timescales down to a few minutes.

IRA FLATOW: And that would be by putting radio telescopes out in space?

MARTIN REES: Well, you could do that, but in fact, already, by infrared interferometry, there’s an instrument called GRAVITY, which is an instrument that’s been developed by someone called Eisenhauer at Munich. And this has proved its ability to actually study moving blobs near the galactic center and I think probably will do a better job on the galactic center than the Event Horizon Telescope has been able to do.

IRA FLATOW: Well, I want to thank you both for taking time to be with us today. Nice to have you back, Martin Rees, United Kingdom’s Astronomer Royal, and Dr. Donald Goldsmith, astrophysicist and science writer, co-authors of The End of Astronauts– Why Robots Are the Future of Exploration. Thank you both.


MARTIN REES: Thank you.

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