Planetary Radio • Apr 27, 2022

The End of Astronauts?

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Donald goldsmith new zealand

Donald Goldsmith

Astrophysicist and Science Communicator

Martin rees

Martin Rees

United Kingdom’s Astronomer Royal

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

Do we need to send humans into space? Won't robots soon be smart enough and capable enough to do this dangerous work for us? These and other questions are explored by Martin Rees, Britain's Astronomer Royal, and astrophysicist/science author Don Goldsmith in their thought-provoking new book, "The End of Astronauts: Why Robots are the Future of Exploration." They present their arguments in this week’s show. Then we climb Mount Kaplan with Bruce Betts to learn who has won the weekly space trivia contest.

First Humans on Mars (Artist's Concept)
First Humans on Mars (Artist's Concept) This artist's concept depicts astronauts and human habitats on Mars.Image: NASA
End of Astronauts book cover
End of Astronauts book cover The book cover for The End of Astronauts: Why Robots are the Future of Exploration by Donald Goldsmith and Martin Rees.

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Trivia Contest

This Week’s Question:

What was the last spacecraft to do a Venus flyby? Venus orbiters do not qualify.

This Week’s Prize:

A copy of “The End of Astronauts: Why Robots are the Future of Exploration

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, May 4 at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

Who was the youngest person to walk on the Moon at the time he walked on the Moon?


The winner will be revealed next week.

Question from the April 13, 2022 space trivia contest:

Where in our solar system is a mountain named Kaplan?


Mount Kaplan is the tallest peak in Antarctica’s Hughes Range here on Earth.


Mat Kaplan: The end of astronauts? This week on Planetary Radio. I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. Space is hard. It's also dangerous especially for living things like human beings. Does it make sense to send astronauts at great expense into deep space? This is the question asked by Donald Goldsmith and UK Astronomer Royal Martin Rees in their new book, The End of Astronauts: Why Robots are the Future of Exploration. Whether you agree with their arguments or not, I think you'll find our conversation both stimulating and thoughtful. It will be followed by an opportunity to win their book when Bruce Betts brings us yet another space trivia contest in What's Up.

Mat Kaplan: I'll be leaving for Washington, D.C. soon. I'm very excited to once again attend and help host the Humans to Mars Summit from Explore Mars. The summit's return to an in-person gathering runs May 17 to 19 at the George Washington University. The all-star list of participants includes many past Planetary Radio guests and a lot of other folks I look forward to chatting with for our show. Planetary Society is once again a co-sponsor of this great event. Want to join us in D.C.? You can learn more and register at I hope to see you there.

Mat Kaplan: April 22nd was Earth Day. That explains the beautiful Earthrise image of my favorite planet that tops the April 22nd edition of The Downlink. The Planetary Society's free weekly newsletter includes a recap of the Planetary Science and Astrobiology Decadal Survey we talked with Casey Dreier about last week. There's a link to Casey's in depth analysis of the recommendations. We also learn that the United States is ending at least one type of anti-satellite weapons testing and is called for other nations to do the same, and there's a celebration of Ingenuity's first year in the thin air over Mars. The plucky little copter made 26 flights, lasting a total of 46 and a half minutes and traveled nearly six kilometers. I expect someday, we'll see it take a place of honor in the Smithsonian Institution's Mars based annex. More is waiting for you at

Mat Kaplan: Astronomer Royal Martin Rees was professor of astronomy and director of the Institute of Astronomy at the University of Cambridge. He's a past president of the Royal Society. Among his many awards are the Templeton Prize and the Inaugural Fritz Zwicky Prize. The author of hundreds of papers and many other books has now teamed with Donald Goldsmith to create The End of Astronauts. Don is an astrophysicist and the author of books including The Runaway Universe, Exoplanets, and with Neil deGrasse Tyson, Origins. He has received lifetime achievement awards from the American Astronomical Society and the Astronomical Society of the Pacific. With credentials like these and a carefully considered argument, it was inevitable that their new collaboration would receive a lot of attention. They recently joined me in an online conversation.

Mat Kaplan: Donald, Martin, thank you very much for joining us on Planetary Radio, and thank you for this deeply thought provoking book, which is also, I would say, simply provoking, which I'm sure is something that you fully expected. Welcome.

Martin Rees: Good to be with you.

Don Goldsmith: Thank you.

Mat Kaplan: I want to thank you, first of all, for relying on and crediting the work of several of my Planetary Society colleagues in your very extensive references and notes. You mentioned Casey Dreier, our senior space policy advisor, the great John Logsdon, a new colleague, Jatan Mehta who writes features for us. You even have a mention in further reading of that wonderful discussion that took place back in 1973, Mars and The Mind of Man, that involved two of our founders, our late founders, Carl Sagan, Bruce Murray, Arthur C. Clarke, Ray Bradbury, Walter Sullivan. I'm sorry to say none of them are with us anymore.

Mat Kaplan: I will also note upfront the thesis, your major thesis in this book is heresy to many of our listeners or at least fighting words. I'm sure you knew you would, as I've said, see resistance from fans of human space flight, right? Did this come as a surprise, Martin?

Martin Rees: Well, you must exaggerate our view. We are not looking very far ahead. We're looking 20 or 30 years ahead. We accept there will be people in low Earth orbit, but what we do say, and I don't think this should be too controversial, is that it's very, very hard to send people to Mars and back compared to sending a robot, and for exploring, clearly, we're going depend on robots and not humans on that timescale.

Mat Kaplan: This would explain why we haven't already been to Mars since that has been talked about for so long.

Don Goldsmith: Of course, we wanted to be controversial by asking the fundamental question, how important is it? Is it just as simply that we must do it? Is it our destiny? Shouldn't we stop and think about the cause, the dangers, the comparison with robotic exploration? Martin is a little more generous than I. Even with the moon, it's not at all clear why we need to send astronauts to the moon as we once did to fight the Chinese or mine the moon or establish a moon colony for purposes uncertain. In the next few decades, wouldn't it be wise to do what we do so well without risking human life and doing it far more cheaply? At least, people should talk about that instead of saying, "Why are you bothering to bring this up? We must go."

Mat Kaplan: Let's follow up on that mention of destiny, having a role. You paraphrased philosopher James Schwartz when you say that the desire to explore, that it's not in our destiny, and neither is it in our DNA nor innate in human cultures. Could you expand on that because there are folks out there who see this in all three of those factors?

Don Goldsmith: It's a good question to talk about it but even if destiny is in our culture and our DNA, we are exploring. The question is, do we have to do it in person? It's just assumed that if Columbus set foot on existing shore, then we must. In fact, we've got wonderful exploration going on on Mars, for example, right now. It's human in the form of emissaries we built.

Martin Rees: If I can add to that, I think we've got to think about time scales. We're talking in this book about certainly not more the century ahead and mainly a shorter time scale with that, but let's remember that the sun will be there for six billion years, and human beings will have evolved into something quite different long before that. So, when we say that it's not our destiny, we think it's not the destiny for flesh and blood humans to go very far into space.

Martin Rees: If I can jump to towards one of the later chapters in our book, I think we do suspect that by the end of a century, there will be some privately funded adventurers living on Mars, having gone on a one-way trip. Those guys will have every incentive to use all the technology of gene modification and cyborg techniques to adapt themselves. Those guys will become a new species within a few hundred years. Having done that, if they become inorganic, they won't need an atmosphere, and they may be near immortal, and they will have a destiny need to go for the deep space. So, it's our progeny who will but not flesh and blood creatures like us.

Mat Kaplan: Homo galactus, perhaps.

Martin Rees: Right?

Mat Kaplan: I've heard you make this point on other programs and in some of your writing as well. For the more immediate future, it is this distinction that you draw between government-supported human space travel and corporate or privately supported space travel, which currently both of you are still quite open to, Don.

Don Goldsmith: I only worry about the fact that even privately funded space travel could say go to Mars and start ripping things up and destroying certain key evidence. As a general proposition, it's true, I agree with Martin that you can leave this to the people who are crazy enough, eager enough, adventurous enough to want to go into space, currently 1% risk of death. All right. It may even come down and maybe want to go one way to Mars. There are plenty of eager people who wish to do this, but I'm sort of dubious about the whole question of, do you need to do it? It's one thing you say you want astronauts to go somewhere. I want people to concentrate on the key question, do we need to do it? If not, how should we pair down for the next few decades and think rationally?

Martin Rees: A footnote to that, I mean, our view or my view is we don't need to spend taxpayers' money on it. If billionaires and sponsors want to spend money, that's fine, but the reason that they should do it and not taxpayers is that they can afford to take higher risks than we as the public can impose on civilians. As we know, that shuttle failed twice in 135 launches, less than 2% failure rate, but each we know is a big national trauma, but that 2% failure rate is acceptable. So, if adventurers, who are prepared to accept their 10% risk, are prepared to go, they can do it much more cheaply. So, it'll cost the billionaires less than it cost the taxpayer.

Mat Kaplan: I mean, you mentioned the Polynesians who, of course, were intrepid explorers, but you also give the example of China and that the people there seem to be happy to stay in the Middle Kingdom, but there was that period of dazzling exploration in China that then ended apparently by choice, which some would say led to the stagnation of Chinese society for hundreds of years. They're only turning that around now. I mean, what is your response to that?

Martin Rees: I would say it's very poor analogy because the Chinese may have missed the opportunity to go to places at least as exciting and fertile and suited to humans as the kingdom where they were, whereas we're talking about, at huge expense, going to places which are extremely hostile to human beings. So, I think it's not an analogy at all.

Don Goldsmith: If I may beat that horse a bit farther, we're not talking about ending exploration. Far from it. The Chinese of that era had automated probes. It's not as though we're giving up on learning about these objects. We're going to learn far more without sending humans.

Mat Kaplan: Let's turn to that argument that humans are needed just to repair and maintain the robots and the machines that get work done in space. I mean, you give the example of the whole space telescope, the five trips made there to repair it, to upgrade it, but you have a terrific answer to that. Martin, you want to share that with us?

Martin Rees: Yes. Well, it would've been cheaper to make five copies and launch the one after the other than to pay for the shuttle trips to send the people. Of course, the thing about robots is that they are much cheaper to send than humans, they don't need 200 days of food on the way to Mars, and if they stay there, that's fine. We can send some more. As to whether they could do exploring, then of course, the present day ones can't, but if you compare Perseverance with Curiosity, Perseverance is far more able to navigate its way around in a way that Curiosity couldn't. Future probes in 10 or 20 years will have enough geological savvy to decide what's the best place to dig or to observe, and so we think they will catch up, and the gap between the human geologist and the kind of probe you can send will diminish, whereas the cost gap won't diminish. It'll be huge.

Mat Kaplan: Don, I've heard you make a similar point. In fact, you look all the way back to Viking, which had hardly any intelligence at all. How quickly do you expect AI to advance to the point where it might, let's say equal the capabilities or at least come close to the capabilities of a human geologist on Mars, for example?

Don Goldsmith: Before I answer your question, I can't resist adding to the last answer that one point we agree, I think with these astronaut enthusiasts is it's a mighty degrading thought to think that astronaut's greatest achievement would be to repair robots. I mean, how sad to think that. Maybe they could do it, but what an argument.

Don Goldsmith: AI let's look right on Earth. We can't yet have self-driving cars as Tesla keeps proving quite. You see the one that got away from the police up in San Francisco the other day, but obviously, we're not far with a certain amount of risk from having a car that can navigate the entire highway system pretty well. If that's true, they can navigate Mars pretty well too as Martin was just saying.

Don Goldsmith: As to the ability of a human versus out of a robot, I found this wonderful quote from my friend, Chris McKay who's a geologist with great pride, obviously, because he said with five doublings of ability from our current status, that's 32 times better. You could have something equal to a geologist assistant on Mars. I was wondering just how wonderful are humans that way.

Don Goldsmith: A robot nowadays comes with a big brain, full of AI and if necessary, could even radio back to Earth. There's no hurry, and they ask about things that they've found. I would say that well within the timeframe we're talking about of 20 years, you could send a machine to Mars that would equal what a geologist could do in terms of interpretation. People say, "Well, only humans can do and deal with the unexpected," seems ridiculous to me. They deal with things in different ways. Maybe I'm just too enthusiastic about machines that way.

Martin Rees: If I can add, I mean, I'm enthusiastic about space structures, to have a huge telescope arrays in space, maybe solar energy collectors, and they can be assembled by robots. They don't need people to go up, and so there are all kinds of uses for these intelligent and adept robots.

Mat Kaplan: Don, I'm glad you mentioned Chris McKay, that great astrobiologist who is a good friend of ours. Chris, of course, was an original member of the so-called Mars Underground, the people who desperately wanted to explore Mars, robotic or human. It's so interesting that someone with that kind of decades long dedication would provide the quote that you gave us.

Don Goldsmith: How about the fact also that he watched the Terra Formars while we're at it?

Mat Kaplan: I was going to get to that eventually.

Don Goldsmith: Chris McKay is a wonderful man. He's devoted his life to Baffin Island and Antarctica, or once together, he dives in a frozen, almost frozen lakes and so on, but his vision of the future for Mars is as scary as that of Elon Musk that we turn Mars into the best copy of Earth we can, which by the way would be a very poor copy, and look what we've done to Earth. I just think pushing these kinds of ideas are, you could talk about them, but the moral implications ... I realize morality is up to individuals. It's staggering that just because we ruin one planet, I may be negative, doesn't mean we have sort of a moral right to go do it elsewhere.

Mat Kaplan: I think you've also made the point, terraforming Earth or re-terraforming Earth will be a much smaller challenge than turning that other planet into a place that welcomes humans.

Martin Rees: That's right. I mean, a few intrepid pioneers can live on Mars, but it's more uncomfortable than being at the top of Everest, the South Pole or the ocean bed, but there's no planet B for all new risk averse people, and dealing with climate change and all that is a dawdle compared to making Mars habitable and terraformed to ordinary people. It's not a worthy go at all. I agree with Don on that.

Mat Kaplan: You also agree with my boss, Bill Nye, who believes it will never happen though we have a five Canadian dollar bet that sometime in the next 10,000 years, we may see a terraformed Mars. The jury is still out. Somewhat of a change in topic here, what did you learn about the public's interest in and support for space exploration?

Don Goldsmith: A very impressive survey work that's been done, which I came across in my research that shows the public is pretty, pretty favorable. The main point about the public is it's doesn't draw the sharp distinction we're trying to. It is understandably all of a piece. NASA, it's wonderful whether NASA is sending a robot to Mars or an astronaut to the moon or something. Space. There's something for everybody there. As I see it, our job in terms of enlightening the public to the extent they wish to be or think about it is just to start by saying there's astronauts and there's robots. Let's think about the difference. As far as the current data goes, as far as I could tell, people like both of them. They're very impressed by the robots and rightly so, not to mention all the things like the James Webb Telescope, which continues to amaze scientists as well as the public. Their horizons are broad, so to speak.

Don Goldsmith: Now, there is a minority that says it's all a waste. Again, they don't distinguish. We should be spending this money here on Earth, where there's plenty of reasons, plenty of good things to spend it on. Shut it all down. Sometimes, even say, Bernie Sanders comes rather close to this, it seems to me. Certainly, that's understandable too. Just because you say you could do it for $1 billion instead of 10 doesn't mean let's spend a billion. Nonetheless, the majority of people like the idea. It cheers them up. It's strange that as we've taken away the night sky from so many people, we've given them the television view of the cosmos, you might say. It's not real compensation because there's nothing to equal getting out on a clear night, but as you know, people can't in most places.

Mat Kaplan: Sadly, yes.

Martin Rees: Public opinion is fickle anyway. Of course, let's remember, if I can say this as a Brit, the U.S. enthusiasm at the time of Apollo was not only this great achievement, but it was a great patriotic achievement to beat the Russians. If you take away that element, it's not so obvious that the extra expenses in humans rather than machines is so easily justified.

Mat Kaplan: What about the power of the transformative moment as you refer to it in the book, which I will just describe as the inspiration that can be provided by seeing other humans, not just robots, because I love the robots too, but seeing other humans walk on another world or any place that it has been unexplored? I would apply that especially to young people who we want to attract to so-called STEM careers.

Martin Rees: Well, it's worth a lot, but is it worth the huge amount involved in sending someone there and bringing them back, and the return ticket's about 10 times as costly as the one-way ticket probably? So, I think it's sort of hard to justify. I'd also counter that perhaps young people may not be quite so enthused as our old generation was because they've seen so much on the movies, et cetera, so many simulations. They won't distinguish that, all that much from the real thing. It was a big deal for us. Of course, we have seen so many space movies.

Don Goldsmith: That's a great idea. We can give them virtual reality to cheer them up, but it is true that humans will always identify more with humans than machines, so it's impressive how these Mars rovers and so on gained a lot of popular tension, you might say, as quasi individuals. I don't see any solution except the one Martin just proposed. As far as inspiration goes, there'll always be low Earth orbit as we've just ... It's a little late to complain about anything in that way anyhow, but the only danger is people blowing themselves up or running into each other once they're in a crowded orbit. As we're going to the moon, well, we've been there, that's never going to excite people, so it is going to Mars.

Don Goldsmith: I'd like to emphasize that nobody, none of these young people or anyone else is dreaming we must go to the asteroids, we must go to Europa or series and investigate life though it would be nice. So, sort of Mars per se. I don't know if we have compromised it possible as Martin was saying. Don't spend public money. Let the adventurers go on a one-way trip. People will identify with them. By the way, they should also be careful to identify with a one-way nature, and that will inspire the young, but when I talk to my grandchildren of whom I have three, at least the ones who are old enough to talk about it, they want to go into space, and they don't ask too many questions about Mars. Space, space.

Martin Rees: One other point I mentioned giving the edge to the robots is that the robots can't go just to Mars. As you would agree, I'm sure, it's not crazy to send them to Europa, Enceladus and places like that, which will make very exciting discoveries. So, that's an order of magnitude harder for humans and probably not feasible at all with present propulsion, whereas one could perfectly well send sophisticated robots to the planets and their moons in the outer solar system.

Mat Kaplan: I will give you a thought that occurred to me as I was reading the book that I look forward to suggesting. It mostly seriously, though not entirely to my friends at NASA, which is that they make the next Mars missions, Mars rovers, Mars landers look as anthropomorphic is possible because I have friends who identified with Spirit and Opportunity because they were cute, and they had two eyes on top of their neck to look around and Curiosity and Perseverance somewhat less.

Don Goldsmith: Also, instead of movies where humans go everywhere, you need more robot explorers. There's the one movie, Wall-E. Am I pronouncing it correctly?

Mat Kaplan: Oh, yes. Wall-E, of course.

Don Goldsmith: Well, there's a wonderful, cute little robot and so on. It doesn't have the same success as Star Wars, but we could get there, but nonetheless, it's not so much the look as the anthropomorphization of the, I don't know, the speech patterns, the messages, but everything. It could be made more that way. On the other hand, you wouldn't want NASA to be caught spending millions upon millions just to do so because it's not right.

Mat Kaplan: Well, maybe Disney could help out from the goodness of their corporate parts. I'll continue our conversation about The End of Astronauts with authors, Don Goldsmith and Martin Rees in about a minute.

George Takei: Hello, I'm George Takei, and as you know, I'm very proud of my association with Star Trek. Star Trek was a show that looked to the future with optimism, boldly going where no one had gone before. I want you to know about a very special organization called The Planetary Society. They are working to make the future that Star Trek represents a reality. When you become a member of The Planetary Society, you join their mission to increase discoveries in our solar system, to elevate the search for life outside our planet, and decrease the risk of Earth being hit by an asteroid. Co-founded by Carl Sagan and led today by CEO Bill Nye, The Planetary Society exists for those who believe in space exploration to take action together. So, join The Planetary Society and boldly go together to build our future.

Mat Kaplan: Martin, you talked about no one is looking to send humans to somewhere like Ceres or the smaller asteroids to look for life, but of course, there are people who very much want to visit those asteroids and chip away at them, do some mining. We've even seen at least a couple of companies who had as their goal doing exactly that. Do you also think that that is something that we may see in the future, whether we should or not, that could get by with just robots, Martin?

Martin Rees: Well, it could get by with just robots certainly. Whether it's going to be a good economic deal, I have no idea to sort of knock the bottom out of the platinum market, et cetera, but of course, we have a whole chapter on space law, and we accept that when this sort of thing starts just as if there starts being hostile attacks by one part on the spacecraft of another, then we do need a legal system, which is not going to be adequate. So, I think we would want more attention to be given to space law, which could apply under these different scenarios.

Don Goldsmith: Although space law internationally is still a dream, when the Chinese go to these asteroids and we attack ... By the way, it's much better because I mean, robot wars are much friendlier. That's the right word. Human wars, that's-

Mat Kaplan: Much less lethal anyway.

Don Goldsmith: Bruce Willis type vision of hard miners wielding their axes or something or their machines and encountering guys on the other side of an asteroid or they're arriving, and they bomb them, just keep it to the machines. I'm totally against all phases, but that's me, and that's Martin saying it's not clear even if they're wealthy. There are three different quotes in our book from three different people who say the first trillionaire will be made on an asteroid. By the way, we may make it right here on Earth if Mr. Musk gets any richer but all right. Everything can be done by machines is vaguely our position. Doesn't mean it will be or even should be if you insist that there's the inspiration factor and the hostility factor. If the Chinese are walking around on Mars, how can we not do it? What Donald Trump would say and many Americans, well, that's a tremendous defeat just like Sputnik beating the Americans into the satellite game. There's no real counter argument to this except to try to get saner.

Mat Kaplan: What about corporate presence much closer to home but still in space, lower Earth orbit or nearby? Let's say one of the LaGrange Points. You talk about this in the book as well. I mean, Jeff Bezos thinks we should move heavy industry and all its pollution out there into space. What are your feelings about this, Martin?

Martin Rees: This is in a very long term indeed, of course. Where that'll happen before human beings change into post humans, I don't know, but I have to say that I find the idea of having heavy industry in space more alluring than the revive of the old O'Neill concept of the sort of Californian suburb in space if I may say that, which seems to be not a very alluring prospect. So, I don't think we want that, but if it's feasible to have some industry in space, and clearly, some can be done better in space, then I would say that's fine.

Don Goldsmith: There's always a transport issue. I mean, it's an economic as well as a pollution factor, just what is it that's going on in space and how do you bring it back to Earth. For example, wonderful if all our energy production were in space, even nuclear, but then what? You don't string a cable and so on. Of course then, of course, which I feel [inaudible 00:27:23] must all live in space than move right next to it.

Martin Rees: Yes, but things are better with the cheaper launchers. The new SpaceX launcher can launch, I think 150 tons in low Earth orbit and incidentally can launch a single mirror as big as the James Webb's mirror in one piece in his nose cone. So, I think the economics of solar energy in space is now credible. When it was suggested by Glaser in the 1970s, it wasn't, whereas now with cheaper launches, et cetera, it's not a crazy idea.

Mat Kaplan: There is another point that you make in the book. I'll summarize it as, what's the rush, Don?

Don Goldsmith: Yes. That is our point. We've been setting these goals around sending ... At least Donald Trump said putting the first woman on the moon and making sure the first person on Mars is an American for some time, and they keep being postponed under simple facts of life. What is the rush? Of course, Martin and I are rather considerably older than we used to be. We'd like to see things happen, but we don't see that as a valid reason for rushing. Many good things are done by careful planning and also adjusting their circumstances. Look what happened with the Hubble. Started as a total failure, thanks to the astronauts, et cetera. It's totally outlived it's projected lifetime. Still working.

Don Goldsmith: We should be careful about these things. We're talking about huge amounts of money and in some cases, human lives. What is the rush? The only one that comes up is competition usually. Well, there's a desire to keep NASA going. They've got to do something, but they're doing plenty as it is. I keep bringing this up to people. They don't seem to worry about it, but I think if the Chinese really get active with humans in space, there's going to be seen as a tremendous spur that we must catch them and surpass them. But that's the only rush that I see.

Mat Kaplan: A new space race. I want to come back to what you touched on when we talked about not just terraforming but any human presence on Mars, and that is planetary protection, responsibility that we share to avoid contamination of what could be another biosphere, whether it's Mars or Titan or someplace else. Should this be an even bigger concern? And do you think the level of concern that's currently being given is adequate?

Don Goldsmith: Scientists are highly concerned even by going back to Viking. The sterilization program, as understood, couldn't do everything, or you'd ruin the instruments. Suppose you land on Mars as we have, gather samples as we're doing, and get ready to bring them back. It should happen within 10 years. Perhaps even Martin and I will be here to see it. We could be pretty sure, though not 100.0%, that whatever is in those samples is not contaminated. Therefore, if you found traces of life of any kind, it'd be wonderful, and you could immediately ask, is it Earth life? Our DNA, or not? The more you spread our DNA around in any form, the more difficult it would be, not of course if it turns out you found life that was very different from ours at the fundamental level, but it turned out to be the same, implying there was Panspermia transfer, life from one planet to another, you would never know for sure whether that was recent transfer that we brought or ancient transfer. I guess you could try to work harder to figure it out.

Don Goldsmith: So, the more we can protect Mars this way, I say Mars in particular because of course, that's where the action is for now in looking for extraterrestrial life, the better off we'll be. I can't say that we're doing enough so farm and we certainly won't be doing enough when these partly privately funded expeditions go to Mars. I doubt that they're going to act like they're concerned, but they won't really be doing much about it. So, I'm a little worried there. The good news is before they get to Mars, we should be able to get some real sample returns going starting with the Perseverance ones, and NASA has further plans, but in the long run, we're going to contaminate. I only hope it's more modest than it could be but much, much worse.

Martin Rees: No, I agree with that, but of course, we can still continue the search robotically for life under the ice of Europa or Enceladus, and that would be more important because everyone knows that if life existed on Mars, it could have had a common origin from life on Earth, but I don't think that could be so credibly stated of life on a moon of Jupiter or Saturn.

Don Goldsmith: Martin suddenly cheered me up because as I mentioned, Mars is where people concentrate. We're not going to hear about one-way missions to Europa to settled [crosstalk 00:31:42].

Martin Rees: [crosstalk 00:31:43 ]. Yeah, that's one for the robots clearly.

Don Goldsmith: [inaudible 00:31:47].

Mat Kaplan: Not in our lifetimes. Returning to the less rational, both of you and I are old enough to remember when humans stepped on the moon certainly for me and I suspect for you as well. It was a wonderful moment. It was a great moment of pride and inspiration. This is likely, in spite of the arguments you make in your book, this is likely to happen someday on Mars though it's certainly proving to be much more difficult than was thought at the time of Apollo. If we're all lucky enough to be around, won't you feel that this is some kind of a great milestone for the human species, Don?

Don Goldsmith: Well, yes. By the way, let me recall that I was in the press room with JPL the night that Viking 1 touched down on Mars.

Mat Kaplan: I was in the auditorium, was standing with Ray Bradbury and some other folks, and what a moment that was.

Don Goldsmith: It made a deep impression around the world not as much, I guess, as the first humans on Mars, but we had that ... It came and it went. I would certainly feel a common human pride even if it violated some sort of detailed argument we're getting into here, depending on who it is. Is he Chinese and so on, but from that point of view, you should do it once. Look, we went to the moon. We had this great inspirational moment. It ended, it'll be 50 years come December, the last human on the moon. Okay. We did it. You could say if that was a problem, let's do it once. I might almost favor that if it meant we could relax about it, not do it anymore.

Mat Kaplan: Martin, would you be among those applauding when that first woman steps on Mars?

Martin Rees: Certainly. I mean, just to say that at the time of the Apollo, I think many of us thought it would only be a decade or two before the world footprints on Mars, but as we know, NASA funding, which had been huge to beat the Russians was appropriately choked off then, so that's why the project lost momentum, but I would, and I think Musk has said he wants to die on Mars but not on impact, and in 40 years time, he might make it and to be the first person to get to Mars, to be the first person to die on Mars would be a great achievement. I'd be happy with either of those.

Don Goldsmith: For him, you mean?

Mat Kaplan: Gentlemen, you have, as I said, created a most thought provoking book. I enjoyed it. I recommend it. The book is The End of Astronauts: Why Robots are the Future of Exploration, and if you have heard this conversation, listeners, and you have been shaking your head and your fist at your talking box the entire time, I still recommend you read this book very highly. Gentlemen, thank you for joining us and for providing this provocation.

Don Goldsmith: Thank you, Mat.

Martin Rees: Thank you very much. Good to be in touch.

Mat Kaplan: Astronomer Royal Martin Rees and science writer Donald Goldsmith. The End of Astronauts is published by Harvard University Press. Time for What's Up on Planetary Radio. Here is the chief scientist of The Planetary Society. He's with us every week. It's Bruce Betts, and he's here to tell us about the night sky and much, much more. Welcome back.

Bruce Betts: Thank you. Good to be back. I've got exciting stuff to tell you as always.

Mat Kaplan: As always.

Bruce Betts: Pre-dawn sky in the east, still a planet party and in fact, Venus, super bright, brightest night sky object besides the moon natural object. Jupiter, second on that list. Oh, my God. My dog is so excited about it. We'll be very close to each other on Saturday, April 30th in the morning. I can't tell you how playfully excited my dog is about this. My other dog plans on sleeping through it because he just doesn't do pre-dawn, but if you do, they will be closer than the width of a full moon to each other, and if you look to the upper right, you'll have a couple more planets, reddish Mars and yellowish Saturn. Jupiter will go up higher than Venus over the following days, and they'll separate, but they'll still be close and make for quite the lovely view over in the pre-dawn east.

Bruce Betts: We go on to this weekend's space history. It was 1949, the Gerard Kuiper discovered Nereid, moon of Neptune, one of the many small moons. We just reflected back on the late '90s comet Hale Bopp recently. Well, it was 1996 that comet Hyakutake was the closest to the sun. Hyakutake Hale Bopp giving us nice shows a couple years in a row back in the late '90s.

Mat Kaplan: I've said it before. I need another one.

Bruce Betts: Oh yeah. We should arrange that. I'll start making some calls. Onto Random Space Fact.

Mat Kaplan: That was so straightforward.

Bruce Betts: I thought I'd be different. Mariner 1. You remember Mariner 1. It didn't go very far. Fortunately, there was a Mariner 2 that became the first flyby, successful flyby of another planet of Venus, but poor Mariner 1 was launched on an Atlas-Agena rocket, and shortly after liftoff, it went off-course, and range safety blew it up. The errors were traced to omission of a hyphen-like symbol in one of the guidance program characters. Anyone who's done programming coding knows the heinous pain of having a symbol that's not in the right place.

Mat Kaplan: Really?

Bruce Betts: But you'll like this. Arthur C. Clarke, famous science fiction author described the error as the most expensive hyphen in history.

Mat Kaplan: Oh, Sir Arthur. You were a card.

Bruce Betts: I thought you'd like that. Hopefully, you enjoyed the trivia question, Mat.

Mat Kaplan: I did.

Bruce Betts: I asked the world where in the solar system, where in the solar system is there a mountain named Kaplan, which I'd like to think was named after you, but maybe we'll hear otherwise. How'd we do?

Mat Kaplan: I thank you, first of all, for this birthday celebration question. I wasn't the only one who enjoyed it. A lot of people enjoyed it. We had more entries than we have had in quite a long time. Here is the response from Dave Fairchild, the poet laureate in Kansas. If you look around in space for mats out in the void, there's one that's known as Kaplan, but it's an asteroid. So, if you want to find a place you actually can go, Antarctica is where you'll find Mount Kaplan in the snow.

Bruce Betts: Indeed. Kaplan is on Earth, the mountain. I tried to find you something elsewhere in the solar system, but Earth's a pretty good place.

Mat Kaplan: I like it. As you know, as Bill Nye says, most of my favorite people live here. Norman [Kusun 00:38:39] in the UK gave us a lot more details. "It's a big mountain appropriately. It's huge. It's, let's see, almost 14,000 feet, just over 4,200 meters. It's the biggest one in the Hughes Range of Antarctica, and it was discovered and photographed by Admiral Byrd on his flight made in 1929, but it wasn't named," says Norman and a whole bunch of other people, "until 1957, in '57, '58. It's named after ..." Oops, not me.

Bruce Betts: Oh.

Mat Kaplan: Joseph Kaplan. He was the chair of the U.S. National Committee for the International Geophysical Year, which was 1957, '58. So, good on you, Joseph. I'm just going to have to wait my turn, or as Barry Olson says, Barry in Alberta, Canada, "Sorry, Mat. Perhaps in another universe." Okay.

Bruce Betts: That's true. I didn't open it up to another universe.

Mat Kaplan: Here's our winner, Octavio Lamas. He's a first time winner in Arizona. He kept it simple. He just said, "It's on Earth, and that's good enough." Octavio, thank you for entering. We're going to send you, Fred Haise's great book, Never Panic Early: And Apollo 13 Astronaut's Journey by Fred Haise with Bill Monroe. Fred Haise, that Apollo 13 astronaut. Thank you, everybody who let us know how much you enjoyed that conversation with Fred.

Mat Kaplan: I got more. Of course, I have more. Ian Gilroy in New South Wales, Australia, he says, "In cosmic terms, Mount Kaplan is right on your doorstep, Mat. Just a mere 8,413 miles south of Pasadena, and so even closer to me since I live in the San Diego area."

Bruce Betts: You're practically there.

Mat Kaplan: I've wondered what that chill was, that chill in here. Maya Soukup in Newfoundland, Canada and others mentioned that it has not yet been climbed. So, she suggests that you and I reach the summit. Now, Hudson Ansley in New Jersey suggests that you simply pay for my trip.

Bruce Betts: If you climb that mountain, I would seriously consider paying for it, but we'll have to discuss the reality. You have to actually climb it though. No helicopters.

Mat Kaplan: No, I agree. That's only fair, but I would want 50% up front. I think that's only fair as well. Pavel Kumeisha in Belarus, "This mountain has good company on Earth in the form of Nye Mountain and Betts Hill, both located in North America." Didn't you have Betts Hill once as the response in the contest? Seems like I remember that.

Bruce Betts: I don't recall, but I do now question why I only got a hill, and you got a mountain but-

Mat Kaplan: Let's not make-

Bruce Betts: I suppose that's par for the course. Let's not make a what? What? I feel a pun coming.

Mat Kaplan: Yeah, right. Well, a mole hill.

Bruce Betts: Maybe-

Mat Kaplan: [Eson Beguit 00:41:44], Ontario, Canada-

Bruce Betts: Betts Hill is not just a mole hill.

Mat Kaplan: I believe one of the mountains of the equatorial ridge of the Iapetus is a great candidate to be named Mat Kaplan. I'll take it. Thank you, Eson. That'd be fine with me.

Bruce Betts: Good stuff except for that me paying for you to go to Antarctica.

Mat Kaplan: Well, you don't want to pay for me to go to Iapetus either so ... although you might be more open to that. I got one more. Gene Lewin in Washington who sends us so many great poems, he was talking about the IGY and what a magnificent endeavor it was back then to bring us all together, kind of kicked off the space age and mentioned that he listens to us sometimes on KBFG 107.3 FM, which is a low-power FM station, LPFM up there in Washington, and I just ... I couldn't help wondering if BFG stands for big friendly giant. I hope so.

Bruce Betts: I think that's the best possible option.

Mat Kaplan: Here's a little piece of the poem that Gene sent us this time. "If you want to hear Mat Kaplan up here in the Pacific Northwest, an LPFM of a hundred watts may just satisfy your quest," and I don't have the next stanza. I thought I'd put it down here. Sorry, Gene. It was the one that says, "Hey, if we're not near you on a radio station, every Wednesday, you can catch the podcast." You got something new for us?

Bruce Betts: I was composing poems because that's what I'm so good at. If you want to find Mat Kaplan, go to Lapland. That's it.

Mat Kaplan: Can I just say stick to your day job?

Bruce Betts: Yeah, it wouldn't be the first time. You've said it or anyone else has said it, but let's move on to the next trivia contest. Here's your question. What was the last spacecraft to do a Venus flyby. Orbiters of Venus do not count for the purposes of this question. The last spacecraft to do a Venus flyby. Go to

Mat Kaplan: You have until May 4, May 4, 2022 at 8:00 a.m. Pacific time to get us the answer to this one. I bet you can guess what book we're giving away. It's The End of Astronauts by our guest this week, Don Goldsmith and the Astronomer Royal, Martin Rees. It is provocative, as I said, but a very fun read as was my conversation with them. With that, we're done.

Bruce Betts: All right, everybody. Go out there and look up the night sky, and think about if you were to name a mountain after someone, who would it be? I wanted it to be you, Mat, but I don't know. Can you have two mountains? Wait, let me look outside just a second. Yep. There's a mole hill. It is now Matt Kaplan. Thank you and goodnight.

Mat Kaplan: He's Bruce Betts, the chief scientist of The Planetary Society with that mole hill in his backyard. I will be over there tonight, Bruce, to plant a flag in it.

Bruce Betts: Make sure you bring a little tiny flag.

Mat Kaplan: As we finish this edition of What's Up. Planetary Radio is produced by The Planetary Society in Pasadena, California, and it's made possible by its delightfully human members. Human or AI, you're invited to join them at Mark Hilverda and Rae Paoletta are our associate producers. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. Ad astra.