Planetary Radio • Feb 23, 2022

Astrobiologist David Grinspoon on life, the universe and everything

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David grinspoon

David Grinspoon

Astrobiologist, science communicator and author

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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

Astrobiologist, planetary scientist, author and science communicator David Grinspoon has just been named a lifetime fellow of the American Association for the Advancement of Science. He returns to Planetary Radio for a wide-ranging conversation about the state of our search for life across the solar system and beyond. We also learn what it was like to grow up in a home visited regularly by Carl Sagan and Isaac Asimov. Plus, get out your pencils and calculators! Bruce Betts delivers another cosmic arithmetic challenge in the space trivia contest.

Venus: North Polar hemispheric view
Venus: North Polar hemispheric view Magellan RADAR images are combined with topographic information to create this view of Venus' surface centered on the north pole. Resolution reduced by half from original. Created in 1994.Image: USGS
Color view of the plumes of Enceladus
Color view of the plumes of Enceladus A true-color view of Enceladus' southern plumes.Image: NASA / JPL-Caltech / SSI / Kevin M. Gill
Titan beneath its atmosphere
Titan beneath its atmosphere In this image from NASA's Cassini spacecraft, you can see beneath the atmosphere of Saturn's moon Titan to its surface features.Image: NASA/JPL/University of Arizona/University of Idaho

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Trivia Contest

This Week’s Question:

Bruce’s Messier Math: What is the number of objects published in Charles Messier’s 1781 catalog multiplied by the Messier number of the Trifid Nebula minus the Messier number of the Starfish Cluster?

This Week’s Prize:

A Planetary Society Kick Asteroid r-r-r-r-rubber asteroid!

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Complete the contest entry form at or write to us at [email protected] no later than Wednesday, March 2 at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

In 2021, what were the top three professional asteroid survey for near-Earth asteroid discoveries?


The winner will be revealed next week.

Question from the Feb. 9, 2022 space trivia contest:

Name all the Olympic athletes who appear in pictures encoded on the Voyager 1 and 2 Golden Records.


Five 1972 Olympic athletes appear in pictures encoded on the Voyager 1 and 2 Golden Records: Valery Borzov, Motsapi Moorosi, Cathy Rigby, Edwin Roberts and Su Wen-Ho.


Mat Kaplan: Astrobiologist David Grinspoon and the search for life this week on Planetary Radio.

Mat Kaplan: Welcome. I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. David Grinspoon was last heard here when he joined Alan Stern to talk about their book, Chasing New Horizons, the best-selling chronicle of the New Horizons mission to Pluto and beyond. David has written other popular books over the years as he has continued his research at the Planetary Science Institute. Now he has been named a lifetime fellow of the AAAS, the American Association for the Advancement of Science. David will join me in a few minutes for a conversation that will run the gamut from the possibility of past life on Venus to what it was like growing up with Carl Sagan and Isaac Asimov as regular house guests. Then, you asked for it, the chief scientist has another cosmic arithmetic challenge for you, and Bruce has a rubber asteroid for the winner.

Mat Kaplan: What light through yonder prism breaks? I couldn't resist parroting that headline at the top of the February 18 edition of the Downlink, The Planetary Society's free weekly newsletter. Beneath it is the complete visible light spectrum of our own star and a teaser for the new article about spectroscopy that's also on our website. And then there's the truly beautiful video my colleagues have produced about the same topic. It's all at, where we also wish a happy first anniversary on Mars to Perseverance. Check out the Rover's terrific accomplishments over the last earth year. It was the announcement by the AAAS that reminded me to invite David Grinspoon back and also led me to David's great 2003 book, Lonely Planets, that I'll have more to about in a moment.

Mat Kaplan: Others have already said a lot about it. Astronomer and pioneer SETI researcher, Frank Drake described it as superb. Everything is here. Theories of planetary formation and evolution, the origin of life, the origin of complex life, and even the evolution of intelligence and technology. David has succeeded marvelously at producing a comprehensible, enjoyable overview of astrobiology. The epitome of multidisciplinary research. Apollo astronaut and planetary defense expert, Rusty Schweickart adds David has written the book I wanted to write, and he's done it so very well that I'll be forever thankful I never got to it. David's style is so direct, so personal and so punctuated with delightful humor that reading this book feels like a living room conversation.

Mat Kaplan: Let's start our conversation. David Grinspoon, welcome back to Planetary Radio. It is such a pleasure and an honor to congratulate you on your recent election as a 2021 fellow of the AAAS, the American Academy for the Advancement of Science. So, congratulations and welcome.

David Grinspoon: Thanks very much, and it's great to be here, wherever here is, and have a chance to talk with you some more.

Mat Kaplan: You said in your book, Lonely Planets, which we'll talk a lot about I'm sure ... and I've already said some nice things about ... you say you picked up degrees in the two least practical things you could think of, philosophy and planetary science. But I say thank the maker because they enabled you to think the way you do and to share those thoughts with the rest of us. Lonely Planets, which as I told you, I finished a couple of days ago, has profoundly affected my own thinking and I'm now reading your 2016 book, Earth in Human Hands: Shaping our Planet's Future. Here's what my boss, Bill Nye, says about it. In his wonderful writing style, Dr. Grinspoon spells it out. A single species is inducing more profound changes to our planet than any other organism in geologic history. It's us. If you have family and friends here on earth, read this book, the earth is in our hands. Wow. Nice work. Nice work, boss and nice work, David.

David Grinspoon: Yeah, thanks a lot. It's always nice to hear that and I appreciate the words coming from somebody like Bill. Wow. It's gratifying. I do see a line between all these things you mentioned, because I feel like planetary science does give us a unique perspective on ourselves on this planet, and the point of view of astrobiology of thinking deeply about the relationship between life and its planetary home, which to me is really what astrobiology is about. It's about the relationship between a planet and its life ... gives us a different cast on thinking about ourselves and our challenges as we face the future. So to me, there's some way in which it all fits together, the philosophy and the planetary science and the astrobiology, and then worrying about how all that can affect how we can go about trying to solve our problems as we confront the fact that, "Hey, we live on a planet and we are a force on this planet." We're realizing that. What are we going to do about it?

Mat Kaplan: I promise we will come back to this topic because it is so much at the core of this book, Earth in Human Hands. I'm thinking of this honor that has just been paid to you by the AAAS. The popularization of science by a scientist is clearly not as dangerous a path as it was not that many years ago. I'm thinking now of the National Academy of Sciences and how it snubbed a very accomplished researcher named Carl Sagan back in 1992, who you happened to grow up with, or at least he was a figure in your household. He was just a little too far ahead of his time, do you think?

David Grinspoon: Yeah, I was very aware of that. When I was a student studying planetary science and somebody that knew Carl and was in his orbit because I would hear those snubs. Not just in the high profile media places, but even I had a physics professor, a cosmology professor when I was an undergraduate at Brown, who would go out of his way to make gratuitous anti-Sagan comments. It was puzzling, but it definitely was not considered to be correct for a serious scientist at that time to spend too much of their energy on communicating with the public. The word was popularizer. It was a pejorative term. If you were just a popularizer, then you were obviously not a serious scientist. Some of that was probably tinged with jealousy because Carl was on the Johnny Carson Show, my cosmology professor wasn't, and he was obviously doing very well materially through all this, but I think it gradually also dawned on the community that he had done us a huge, huge favor, because ultimately what we do is dependent upon public support.

David Grinspoon: So beyond issues of whether it's a valuable thing in its own right, which of course it is to try to talk about what we do and spread the word and spread understanding, if you want to maintain your support, it's tax dollars that are supporting us, then of course you need to share the knowledge and share the wonder. Carl was better at doing that than anybody. He was a master at that. There's one more element while we're talking about why Carl was ostracized a little bit in the community that I think is often not mentioned. That is he was also a political activist. He got arrested at the nuclear test site and was involved in several anti-war causes and anti-nuclear weapons causes. That was also seen as maybe not quite proper, that if you were an academic, you shouldn't be an activist and out there protesting.

David Grinspoon: But I think, again, for Carl, it was just he was principled person and he saw it as important, and he saw that he had a platform. And I think that there's a line between that and today, some of the really visible climate activists are scientists who are thinking, "Hey, it's not enough to just talk about this in academic journals. We have to go out and talk to the people about it and talk to our representatives because we see an emergency here and you can't just sit back and make notes and write journal articles when you see an emergency happening. You have to get out there and try to be involved." And, that was the way Carl approached things and not everybody liked it back then.

Mat Kaplan: He certainly did my audience and me a great favor because now it's the rare scientist that I talk to who doesn't think that talking to somebody like me and my audience just ... That's part of the job. That's what we're supposed to do. Thank you, Carl.

David Grinspoon: Yeah, there's been a sea change and now certainly professional scientists and students ... students coming up and early career scientists are all about science communication and using lots of platforms, using social media, and really good at it. There are a lot of really good science communicators. It's largely because it's become something that is valued, that is seen as not just okay, but you get points for spending time on it and being good at it. And, Carl really did. That's one of the ways in which he changed the world was he was really influential in leading the way and showing how you could be a "serious scientist" and really put yourself into communicating well, as he did.

Mat Kaplan: Sounds like you're speaking personally as well.

David Grinspoon: Well, I think so. My career has been unusual. I've been a university professor, I've been a museum curator. I've been a research scientist. I've worked in a government lab. But I've always had, I would say roughly, 50/50 balance between spending my time on research and spending my time on things that can broadly be considered communication and education. And at times, it's been a bit of a juggling act and you feel like you're going to drop the balls because you've got too many of them up in the air, but when it's working well, every part of it enriches the others because in order to be a good communicator, you really have to have a broad base of knowledge and stay educated yourself. Not just on the specific thing you do, but on the field in general. And for a field like astrobiology and planetary science, that's good for your research because you stay educated about what everybody's doing and what's happening in different areas of the field.

David Grinspoon: And then, that comes in and helps you. You can draw upon things that you wouldn't be able to if you were staying more narrow. So at its best, the communication and the research feed each other.

Mat Kaplan: You talk about planetary science, that it may be ... I don't know if you put it exactly this way ... the highest expression of why a multidisciplinary approach is so important in science, but especially in planetary science, and maybe even more so the little circle living inside that Venn diagram circle, astrobiology.

David Grinspoon: Well, there wouldn't be any planetary science or astrobiology without an interdisciplinary approach. If you look at the history of planetary exploration, when we first started sending spacecraft to other planets, there was no such thing as planetary science. It was an interesting question, "Well, who's going to do the science? Who's going to interpret the data?" There were astronomers and there were planetary astronomers, but what they did was look through telescopes and make drawings or photographs and spectroscopy from telescopes and try to figure out a lot about a distant object far away. And then, when we were sending cameras and other instruments to get close up data about the planets, that wasn't really a suitable activity for somebody who had only looked through telescopes their whole life, and we needed to draw upon astronomy, but we also needed to draw upon the earth scientists because earth science had the knowledge of geology and meteorology, which we had to apply to other planets.

David Grinspoon: So, the initial science teams of the first missions were these interesting hybrids of some astronomers, but then they brought in some geologists and some meteorologists. And, those people who I consider the first generation, the people that were on the science teams of the mariners, the pioneers, they had to forge this new multidisciplinary discipline of planetary science. And so, that really came about of the necessity to do the science that became possible because we were starting to send missions to the planets in the 60s and 70s.

David Grinspoon: And then I see astrobiology in a way as an extension of that. There was already this multidisciplinary effort of planetary science, but then when astrobiology became not just a fringe extension of planetary science, which it was at one point when it was exobiology and a few brave souls, Sagan and some others were, were daring to do it on the side ... When astrobiology became an accepted and embraced part of NASA and other space agencies, became mainstream, it required another melding where that multidisciplinary edifice of planetary science, which had been built up already, then incorporated biology and biochemistry and origin of life studies and all this extremophile studies. Basically, it broadened the circle again to include these other disciplines, but the ground had been paved by the fact that planetary science was already this multidisciplinary collection of viewpoints and sources of expertise.

Mat Kaplan: You are an astrobiologist and proud of it. It's your chosen field, but you talk in Lonely Planets, you speculate about whether at least at that time ... This book is a few years old now, published 19 years ago ... whether maybe the focus on astrobiology, eventually the pendulum swung too far that way and caused us to focus too much on places where we might find life; Mars, Europa, to the exclusion of other fascinating worlds. And, I think we're going to be talking about Venus in a couple of minutes here. Do you still feel that way? Has the pendulum swung back?

David Grinspoon: Well, it is interesting to trace fads in our field. I don't want to be too pejorative on anyone's work because there's a quote that I also use in the book from a Greek philosopher, all is a woven web of guesses. That even though we are building on an edifice of knowledge, when it comes to life in the universe, we're profoundly ignorant. And so, there is the danger of group think where everybody's thinking about Mars, and then we've got this expectation we're going to find subsurface life on Mars, and then we find something that's encouraging, a whiff of methane or hints of underground water and everyone gets excited and thinks, "Oh, we're just around the corner from finding extant life on Mars." Well, there may be, or Mars may be completely lifeless. We tend to focus, get excited about certain areas and neglect other areas.

David Grinspoon: And for a while, Titan was considered to be really off limits because it's just ... Well, there can't be any liquid water there, at least on the surface. And even if there's chemistry, it's in these weird methane lakes. And I think now there's more openness to what we call weird life in possible places like Titan, and I'm sure we'll get to talking about the clouds of Venus, which is one of my favorites. I would even go so far, and I talk about this a little bit in Lonely Planets, even places like Io. Okay. Why would you possibly consider life on Io? Well, there's liquid and there's interesting chemistry and who says it has to be carbon? There's interesting possible sulfur chemistry on Io. So not that I'm saying, "Oh, I think there's life on Io and we should go look for it."

David Grinspoon: But, I definitely advocate casting a wide net, and I think the only places we can really rule out for life in our current ignorance are places where nothing is happening. There's no motion of any matter. There's no transfer of any energy. A totally quiescent place. Because whatever life is, and we could get into the whole natural philosophy question of that, but whatever it is, it obviously involves transformation and organization and energy flow of some kind. So, if there's nothing happening and there are places in the universe, including in the solar system, where there's basically nothing happening, then I would say, okay, there's no life there, but any place where there's flow and transformation and phase change occurring in our current ignorance, I don't think we should entirely rule out.

Mat Kaplan: You said, look for disequilibrium and lots of it, and Io would qualify. Mars, not so much.

David Grinspoon: Yeah, well Mars is an interesting case because there may be micro environments where the necessary conditions are met. There's some energy flow, there's some internal activity. Not very much. Mars to me is an interesting test because my hunch ... and all anyone really has in this field are educated hunches in a sense ... is that life requires a certain level of planetary activity, that life is a planetary property that's much more likely to endure for billions of years, for long periods of time on a planet that's active where there are active geological flows and active atmospheric phase changes and geochemical flows. I mean, the earth has its carbon cycle, its sulfur cycle, its nitrogen cycle. And, Mars is just very quiescent. It has a lot of atmospheric activity and a lot of stuff blowing around and condensing on the surface, but no really internally generated geological activity to speak of.

David Grinspoon: I mean, there's little puffs of ... it's not entirely dead, but it's largely dead. So that bias is made towards thinking that Mars maybe is completely lifeless, but I'm enough of a scientist and enough of a philosopher of science to realize that we really don't know. And then to me, that sets up a really interesting test. I'm very supportive of the search for life on Mars because it's nearby. We can search for life there, and I want to know if I'm wrong about this and Mars can support life in its current more abundant state as a planet, that would be a really interesting thing to learn. Then I would learn that I'm completely wrong in my hunches about where life can exist in the universe. And, I want to know that. And also of course, there's every reason to believe that we may find fossils on Mars because obviously it wasn't so [inaudible 00:19:07] in its early history.

David Grinspoon: And because it's been so quiescent, it's preserved that early history much better than most other places in the solar system. So it's a great place to look for fossil signs of early life. I'm a big fan of Mars exploration. I'm just not holding up great hopes for finding extant life there today. And of course, we could get onto another tangent about this but if you're somebody that's hoping that humans can go and live on Mars and do things on Mars in the future, then not having any martians living today, I would also argue is really good news if that's true. It just makes it much ethically simpler to worry about what we're going to do on Mars if there aren't any martians there today.

Mat Kaplan: Yeah, it certainly cleans things up for people like Elon Musk. You've given me a good opening here to mention something I haven't yet about Lonely Planets, and I suspect also about your other ... Well, I know about the other book and that is the humor that you drop in and the popular culture references, which pop up all the time and really made it not just a profound experience for me to read, but very entertaining. I was laughing out loud periodically. And, you said about Mars in Lonely Planets that the absence of disequilibrium on Mars indicates it is dead. That it is perished, deceased. This is an ex-biosphere, with apologies to Monty Python.

David Grinspoon: Yeah. Well, life is too short to not laugh whenever you can. And, I do love humor in things that I can consume, whether it's books or any media. And I also love to use humor when I can. For instance, giving a public talk. If you get the audience laughing near the beginning, then they're on your side. So this is one of my tips for public speakers if you have any nervousness or stage fright. Start off near the beginning with a joke. It could be a pre-planned one if you don't feel like you can make a spontaneous one, and it just loosens everybody up and makes people feel good and then makes them more receptive to whatever else it is that you want to talk about.

Mat Kaplan: I share that advice with you as well. Where were you on August 8th, 1996? I'll tell you where I was. I was driving along the central California coast with my family coming back from a vacation when I heard something on the radio that made me stop the car, jump out, and do a little dance.

David Grinspoon: Yeah, I know what you're talking about. I had a funny experience that day. Actually, I had just turned in my previous book, Venus Revealed, and I was waiting to hear back. Or, I was at some late stage. I had turned in the page proofs or something, and I was taking a little vacation because finishing up a book is stressful. So, I was unplugging for a few days. My wife and I went to these hot springs in western Colorado in this hippie town where we would go hang out and there'd be these hot springs and everybody ... clothing optional and you'd be floating around naked with a lot of these other friendly, naked people. You're just relaxing, far from the world, far from any care.

David Grinspoon: And, I overheard floating in the hot spring, I overheard this woman say to her friend there in the hot spring, "Hey, did you hear? I heard on the radio scientists have discovered life on Mars." And, I was floating there thinking, "Yeah, right." Because this is the thing one often hears when floating in a hot spring in western Colorado. And so, I didn't really take it very seriously. Then a little bit later, we got tired of soaking, put our clothes on, drove into town to get some lunch. And, as we drove into the little town of Ouray, Colorado, I remember seeing the newspaper boxes on the side of the road, and the first one I saw there was a big headline that said Life on Mars. And I thought, "Oh my God, what?" And especially, among all the many thoughts that flooded, I thought, "Oh great. I just turned in my book and now it's obsolete."

David Grinspoon: But then of course, there was the excitement and running out and fumbling in my pocket for the change, because in those days you still had to get the newspaper. I didn't have an iPad yet. Of course, this is how I learned of the story that you're talking about of the announcement that in these meteorites from Mars, they had found these little shapes and other indicators that suggested to them that there was fossil life in these Mars rocks. Very exciting announcement. And, they had a presidential press conference with President Clinton to announce this.

Mat Kaplan: That of course was ALH84001. I will tell you something that I've never mentioned to anybody, so keep it to yourself. I actually got to hold, years later, a tiny fragment of that Mars meteorite with tweezers at a lab here in San Diego. There was a moment that passed through my mind. I could pop this in my mouth and swallow it before anybody could stop me. As my friend Kim Stanley Robinson likes to tell people he went up on his roof and ate a piece of Mars once. But those fossils, they're a great illustration of how science works or should work, right? Because what's the current consensus?

David Grinspoon: Yeah, absolutely. It was a very exciting announcement. The scientists that published that paper in Science Magazine that led to that, they certainly weren't crackpots. They had found some very intriguing pieces of evidence and a confluence of unusual things about that rock that suggested to them that there had been ancient life there. The current consensus is that there are other explanations. That the little squiggly things they saw that could have been micro-fossils probably were the result of some unusual geological, geochemical formation when there's water trickling through a rock and things are being deposited, and that there were also non-biological explanations for the other things they found. I would say we don't know that 100%. The consensus is that it probably wasn't life that they found, and that's probably true. However, we don't know that for a fact.

David Grinspoon: And, I think one of the things we would love to do as we continue exploring Mars is to find examples of exactly what they found, but find them on Mars in their indigenous context and see what really happened locally geologically there. What those scientists did, they really did us all a favor, because even though the pendulum eventually swung towards thinking, "Well, no, there are probably other explanations," it's our job to come up with other explanations because like Sagan's old adage, extraordinary claims require extraordinary evidence.

Mat Kaplan: Exactly.

David Grinspoon: And, you look for a less thrilling explanation so that you don't get fooled by wanting the thrilling explanation to be true. But, they did us all a favor because I think it caused a lot of people to think about that and ask themselves, "Well, could there be signs of ancient life on Mars?"

David Grinspoon: And then when you thought it through, you had to say, "Yeah, well there could be. Why not?" Everything we know about early Mars suggests that it had conditions similar to the time on early earth when, as we understand it, life was forming. And so, there wasn't any logical reason why we couldn't find evidence of life on early Mars. It ended up invigorating the field of exobiology and really helping to birth the field of astrobiology because it got people thinking. It stirred the imagination. I regard it now as probably a mistaken result, but a very fruitful and useful and productive mistaken result.

Mat Kaplan: Lost the battle, but won the war.

David Grinspoon: Right.

Mat Kaplan: You don't want to leave now. David Grinspoon and I will be right back with more of life, the universe and everything.

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Mat Kaplan: If you were writing Lonely Planets now, or if you ever come out with a new edition of it, would you be including Enceladus?

David Grinspoon: Oh, absolutely. Yeah, Enceladus is one of the delights of solar system exploration. There were hints even with Voyager in the early 80s that there was something weird about Enceladus because it's so bright, so anomalously bright, like it's being coated with fresh snow, which it turns out it is. But then with Cassini, of course, we saw that Enceladus is squirting bits of its interior out into space and has anomalous heat flow. And clearly, not only is there something unusual going on inside, which has to do with liquid water that seems to have organics in it, but there's unusual energy source and heat flow. It's the place where not only might there be life, but there might be life that's accessible for us to find because it's squirting its insides out and splattering them on its surface.

David Grinspoon: So in theory, you could go and scoop up some snow and find micro-fossils on the surface of Enceladus. That discovery was tremendously exciting. I actually had an unusual window into that, if I can share a brief story, because I used to work at the Southwest Research Institute in Boulder. One of my good friends and colleagues there, John Spencer, was on the Cassini team and he was on the team that operates the infrared thermal sensor on Cassini. And one night, I was in my office late at night and John's office was just down the hall and he said, "Hey, come into my office. I want to show you something." And he had on his screen a thermal map that he had been making of the south pole of Enceladus. And he said, "I can't get this to go away but it doesn't make any sense." There was this massive heat flow at the south pole of Enceladus that shouldn't be there.

David Grinspoon: It's not like it's overly illuminated by the sun. It's less illuminated by the sun. He said, "And, it's strange. I've been looking at some of these images from the imaging team and I could swear it seems as though there's something maybe coming off of the south pole." So because John called me into his office and shared this with me, I think I was maybe among the first people on earth to be aware of the fact that there's something really weird going on on Enceladus. Those are the moments that you just treasure. Looking back now on everything that we've learned about Enceladus and how important it's become in astrobiology, I feel like that night with my colleague in his office where ... This was all unpublished. He was just like, "I think I found something." That's really cool now to just think back on that and look at what's happened.

Mat Kaplan: This reminds me of, and I think it's a quote from Isaac Asimov, another gentleman who had an influence over you very early on in your life ... If it was Asimov, he said something like science progresses less by shouts of Eureka than, "Oh, that's strange."

David Grinspoon: Right, right. No, it's so true. It's always at first, "That's strange" because you have a lot of those "That's strange" moments where then you realize, "Oh, that was a mistake. I calibrated that wrong or I put in the wrong line of code," and it goes away. So whenever you first have a "That's strange" moment, you don't believe it. You try everything you can to make it go away before you show someone else. So yeah, "That's strange" always happens before Eureka.

Mat Kaplan: We already said Carl Sagan. I think you met him or he met you when you were six years old. Isaac Asimov was also a regular at your house. A friend of the family. Two of the three people I most regret never having have the chance to interview, Asimov, Carl Sagan, the other one being Neil Armstrong. My gosh, I'm so envious.

David Grinspoon: Yeah. It is pretty amazing to think back on that. Of course, when I was a kid, they were just these people that your parents knew. They were fun and likable, but you didn't realize that they were like, "Oh wow." You weren't in awe of them, which I guess is good. But actually, the thing about Asimov, how he came into my family's life is pretty interesting because it was totally separate from any of these other connections. My grandmother, Sally, my dad's mother, her husband died pretty young. My dad's father died the day before my dad's 21st birthday, had a heart attack. And she was suddenly a single mother without any means and had to find a job, had to go back to work, and she applied for this secretary job, which turned out to be a secretary for a biochemistry professor at Boston University named Isaac Asimov.

David Grinspoon: Who, at that time, was not a famous science fiction writer. He hadn't even written any science fiction yet. And, she got the job and she was Isaac's secretary for many years, and then they became good friends and long after he was no longer a biochemistry professor, he was a famous writer, and long after he lived in the Boston area because he moved to New York, they remained friends. And, he was a friend of the family ever since. But so that was just a random thing where she answered an ad because she needed a job.

Mat Kaplan: You're Grammy, right?

David Grinspoon: Yes, that's right. She lived from 1900 to 1995.

Mat Kaplan: Wow.

David Grinspoon: Just imagine that, what she saw in terms of technology. Born before automobiles and lived well into the Space Age.

Mat Kaplan: Amazing.

David Grinspoon: She drew me a picture of comet Halley, that she remembered from when she was 10 years old and it filled the sky. We were talking about it, she's like, "Oh, I'll show you." She drew me a little picture on a napkin.

Mat Kaplan: I hope we get one of those before-

David Grinspoon: Oh, man.

Mat Kaplan: ... we check out. Let's go to Venus, and we'll bring it right up to date, because it was only a few days ago as we speak that we learned that the Parker Solar Probe on one of its swings past Venus actually managed to cut through the cloud's invisible light and show us the surface of our hot sister. That must have been sighting for you. You've been a Venus file ... Venus file? I don't know. A fan of Venus for a long, long time.

David Grinspoon: Yeah, it's really exciting. And honestly, surprised me because we've known for a while that there are these bands in the near infrared that allow you to see the surface of Venus at night from the thermal glow. The surface is hot and so it's glowing in the infrared and in the visible to some extent, but mostly that's completely blocked by the thick atmosphere in the clouds. But there are some wavelengths where the light makes it through, enough light makes it through, in between the water and CO2 bands. There's some wavelengths of infrared light. And, we know there's a window around one micron, which is just a little bit long ward of the red edge of the visible. So, it's near infrared. It's just a little bit longer wavelengths than you can see. And so, we've been able to image Venus at that one micron wavelength on the night side.

David Grinspoon: And we've done that from the Venus Express spacecraft and from the Akatsuki spacecraft, but nobody thought that that extended into the visible. Then these images came out and they said, "This is invisible light," and we all looked and said, "No, it's not. They did something wrong." But apparently there are windows that extend a little bit into the visible more than we thought, or their instrument is going out into the infrared a little bit more than they thought.

David Grinspoon: And honestly, I'm still trying to figure it out. But either way, it's very cool because you're definitely ... you look at the images and it fits with the topography of Venus that we know is there from Magellan and from other things. They're definitely seeing the surface of Venus with this instrument that we thought wouldn't be able to. Again, we're back to, "Well, that's weird." And then, I think we're at this point now we're like Eureka. So there's a new way that we can see the surface of Venus just in the red right at that edge between what is red light that you can see and what is infrared light that you can only sense with detectors.

Mat Kaplan: I know what I should have called you, a Venutian. You wrote Venus Revealed, the book you mentioned a few minutes ago, back in 1998. 24 years later, are we finally beginning to see the attention paid to this sister world that is so different and yet so much like us that you and so many others want to see?

David Grinspoon: I think so, yeah. It's been a long road for the Venus freaks of the community. We've been advocating for a long time that we need more Venus missions. I mean, the history is interesting because Venus was the first place we went with spacecraft, and it was the first place that the Soviets went. Mariner 2, the first ever successful interplanetary spacecraft went to Venus and there was a whole rush of Venus exploration early in history of planetary exploration. And then, it stopped and the focus went elsewhere, and that's partly because Venus is an easy place to get to in terms of celestial dynamics. It's the quickest trip. It's the least amount of energy you need, the least amount of Delta-v, velocity that you need to get to anywhere in the solar system.

David Grinspoon: But then what we've learned about it in those early missions was that once you get there, it's one of the toughest places to actually explore because you can't see the surface from orbit. At least, we thought until these recent revelations. And of course, going down into the atmosphere is very forbidding because the temperature and pressure are so extreme and because the clouds are made out of concentrated sulfuric acid. So, it's an easy place to get to, a hard place to do much more than gawk from orbit once you get there. Because of that, there was a bit of a hiatus, and then I also think that once you have that hiatus and the attention goes elsewhere, that feeds on itself because then you have this whole community of people that are excited about Mars and elsewhere, and they're bringing up graduate students who want to keep doing what they're doing.

David Grinspoon: And so, there's this feedback where if you don't do something for a while in space exploration, it gets harder to go back and start doing it. But then what happens is there's such a gap in your knowledge, which is what we have for Venus now compared to elsewhere in the solar system, that it's an embarrassment. And you can really make the case, "Look, if we want to progress in our knowledge of comparative planetology, and especially now with the exoplanets of which we know there are some exo-Venus's, which increase our desire to fill in these gaps in comparative planetology, then we have to go to Venus if we want to crack this uber puzzle of how the planets work and how does Earth fit in with the other plants."

David Grinspoon: We just can't keep ignoring Venus. Some of us have been making those arguments for a while, but they've become persuasive enough recently so that NASA's announced two new Venus missions and the European Space Agency has announced a big new Venus mission, and now Russia and India and China and even the United Emirates, they're all talking about possible new Venus missions. And, of course, the Japanese have Akatsuki, which is there now. So, it's become, for whatever combination of reasons, Venus has become hot again, so to speak, and I'm really, really excited about these upcoming missions.

Mat Kaplan: Do you think that there is a decent chance that all of these missions, including the two NASA missions, are going to help us reveal that Venus might once a long, long time ago and for different reasons have been as hospitable a place for life as Mars was a long, long time ago.

David Grinspoon: There's an excellent chance that we'll answer that question, and I think there's a good chance that the answer will be that it was hospitable, but if it wasn't, that's of course, really, really important for us to know. Recent models that have been done using general circulation models ... the same kind of models we use to predict climate change on earth ... recently we've been able to apply those to Venus really for the first time in a rigorous way. And the results point us towards thinking that Venus may have been habitable for a long time. We have every reason to think that Venus had water in abundance when it was formed. And of course, it's incredibly dry today. So, it seems to be a story of water loss but the big question is when was that water lost? Was it lost early on in a rush of evaporation and solar irradiation? Or, did the oceans last for a long time and escape into space more recently?

David Grinspoon: Or, there's a third possibility that Venus never had oceans, that it was just so hot and there was so much radiation that close to the sun that the water never condensed and was lost to space before oceans ever formed. There are three pictures. It never had oceans. It had oceans really briefly, but lost them quickly, or it had oceans that persisted for much of its history and lost them more recently. When I say recently, I mean, one or two billion years ago, which is recent in planet time. I think that the combination of all these upcoming missions will let us choose amongst those possibilities, and that is going to be great. Obviously, part of me is holding out for wanting it to have been inhabitable for a long time, because that's just such an enticing possibility and it is a real possibility with what we know now, that Venus and earth may have been these two next door neighbor planets that had habitable oceans for billions of years.

David Grinspoon: And, there could have been life evolving on Venus. There could have even been exchange of material between the two planets carrying living organisms. Who knows? That picture is very enticing, but I also need to acknowledge that we're going there to find out, not to just confirm that enticing picture that I want to be true, but to possibly rule it out, which of course would be really, really important as far as being able to contextualize how often earth-like planets end up having stable oceans and stable surface conditions that could facilitate life for long periods of time. Either way, Venus is a big part of our learning how to put earth in context as far as habitability in the universe.

Mat Kaplan: Such an important point, and one that you have addressed over and over, the ability to look at these other worlds and how understanding them helps us understand our own. And, I come back to the Earth in Human Hands: Shaping our Planet's Future, which is absolutely outstanding as I said. Here's a sentence from the book, which may be key to your premise ... and, I'm jumping ahead a little bit. Many species have changed the planet to the benefit or detriment of others. But, there has never been a geological force aware of its own influence. Do you think we're getting any better at managing our own planet? And, as a part of that, how important is it that we study these other worlds?

David Grinspoon: Yeah, it's a frustratingly slow process becoming a species, a geological force that not only is aware of its own existence, but is able to use that awareness to alter its relationship with its home world. And I feel like we're probably at an early stage of that, and yet there's obviously some urgency because we are definitely at the phase now where we've become not just a planetary force, but potentially a danger to ourselves. Arguably, we're not a danger to the biosphere. We're a perturbing force on the biosphere, and the biosphere will go on without us, if that's what happens. But we're definitely a danger to ourselves. The good news is that we have the tools to understand that and we have the tools to change our ... We're not helpless.

David Grinspoon: We have the tools to change our energy supplies and we can see a lot of the components of real sustainable global civilization would look like. It would be much worse if we were in this problem and we had no idea how to solve it. That's not the situation we're in. Whether we have the social technology to solve it is a whole other question, and I'm an astrobiologist ... Damn it, Jim. I'm an astrobiologist, not a world leader. But, one can certainly see that we are becoming more aware of ourselves as a global entity. One doesn't have to be all kumbaya and say, "Oh, we're going to have perfectly functioning world government." One can appeal to just enlightened self-interest and realize that the major players, the powers that be ultimately don't want to destroy the systems that allow all of us to live. That awareness just needs to sink in.

David Grinspoon: You can talk about the Chinese, and I'm not a huge fan of the current Chinese government, but I do see that ... I've been to China and the cities are really polluted and they're aware of that and they want to stop burning their coal. They really want to for their own self-interest, if for no other reason, because you literally can barely breathe in Beijing. So there are these forces where it doesn't require a totally benevolent world government for that awareness of how the planet works to sink in enough to create the changes in behavior. And that's the way I see our evolving self-awareness influencing the species we're going to be on this planet. There's no doubt in my mind that 100 years from now, we'll be completely post-fossil fuels and we'll have modified our global energy resources and we'll have come to a different kind of a relationship with the planet.

David Grinspoon: It's just that we're not doing it quickly enough, so there's going to be some damage. And we'll look back from 100 years from now and say, "Well, why did we take so long to do that?" Just like we look at whaling now. We used to depend on whale oil. Most of us don't anymore. And we say, "Why did we take so long." There are still whales but we did more damage than we needed to. I think fossil fuels, we're going to look back on it the same way.

David Grinspoon: To the other part of your question, absolutely planetary exploration really helps us get a handle on our relationship with the planet. For one thing, it validates our climate models by looking at climate on Mars and Venus and Titan. Number one, we get confidence that our models basically work. They do predict the surface temperature of these planets in an overall sense. Number two, we learn things from the ways in which they don't exactly predict things on those plants. We learn things about climate that we might have missed just from looking at earth now that help us predict future changes.

David Grinspoon: I won't go into a lot of technical details but there are aspects of climate modeling that have been strengthened and phenomena that we've learned about through studying climate and weather on other planets that have really helped us do better at predicting what's going on on this planet. And then, just the overall sense of gaining perspective, you can't really have a handle on yourself as a planetary entity unless you've looked beyond that and seen other unfolding examples of planetary evolution and realized that there are a lot of different ways that planets can evolve. That helps us get a handle on the moment we're at in planetary evolution where whether we like it or not, we have our hands on some of the controls of what's happening on the planet.

David Grinspoon: And rather than hit the buttons at random like we're doing, we can try to understand how this contraption works and be a little more artful in how we interact with it.

Mat Kaplan: There's a transition here that you talk about from homo sapiens, wise apes, to terra sapiens. What do you mean by that?

David Grinspoon: Well, homo sapiens is the title that Linnaeus gave us, maybe thinking aspirationally, when he realized that we were related to the other great apes, but we weren't one of them exactly. He said, "Well, we're the wise ones." I guess you could quibble with looking at some of our behavior, but in thinking of how we need to come to see ourselves and what is really happening in the Anthropocene and what the best case scenario, the best outcome of that is that it's not just that we now realize that we are an influence on the planet, but we take control over what kind of an influence we want to be. And of course, that requires wisdom. And so Terra sapiens means wise earth, and it's my vision for the future of an Anthropocene where we've responded to the knowledge that we're gaining now in a way that allows us to continue in a healthy relationship with our biosphere.

David Grinspoon: And, when I say Terra sapiens, am I talking about the human future? Or am I talking about the future of the planet because it means wise earth? And my answer is it's really both, because it's an identity with the planet, realizing that we have to see ourselves as an integral part of the functioning of this planet, that planetary systems are now in some sense an extension of human systems. It's daunting to realize that, but it's the truth. If we respond to that knowledge by modifying our behavior in a way that allows us to integrate gracefully into those systems, then we've achieved the state that I call Terra sapiens. Again, there's no physical reason why we can't do that. There's nothing we know about the earth's system that would prevent us from doing that. It's just that we have to spread the word and learn to think like the planet that we are.

Mat Kaplan: We are so rapidly running out of time, and there is so much more that I wanted to talk to you about, David, including your feeling that our sense of science needs to return to what people in the enlightenment called natural philosophy. Fascinating topic. I hope you'll come back sometime. As I read Earth in Human Hands, I couldn't figure out why for days now ... actually, as I finished Lonely Planets, which finishes with a chapter that you called Astrotheology ... fascinating. And now with Earth in Human Hands, I've had this song running through my head. It's Pete Townsend's song, I am an Animal. And I don't know if you know the tune, but it's a terrific song. I can't play it for you here on the show because we'd be sued, but it finally hit me last night as I was preparing for this conversation, that song could be an anthem for Earth in Human Hands.

Mat Kaplan: Here's just a bit of the lyrics. I am a human being and I don't believe all the things I'm seeing. I got nowhere to hide anymore. I'm losing my way. And, it goes on from there.

David Grinspoon: I love it. I don't know that song. I'm a big fan of Pete Townsend, though, so I know what I'm going to do right after we get off the phone here. I'm going to go check it out.

Mat Kaplan: You and others, I hope. I am an Animal. I don't know if it's what Pete had in mind, but that's how I'm going to think about it from now on.

David Grinspoon: Cool.

Mat Kaplan: Before we finish, do you have that paragraph that I was hoping you could read from Lonely Planets? Frequently when you ask a guest to do something like this, it's right from the beginning or the very end of the book, but this one happens to be in the middle of the book, page 243, and it's a statement about astrobiology.

David Grinspoon: Oh, yeah. The context is that I'm talking about how science in a lot of ways has been under pressure to be more and more pragmatic, that research needs to be justified by what it can produce commercially or practically. And, that's been a trend in science. And then I write, swimming against this stream is astrobiology. It is not for profit and can't pretend otherwise. We explore space for reasons that are romantic and idealistic. The universe beckons. We want to go because we want to know. With astrobiology, there is no fronting that the rationale is practical or the benefits material. We do it out of our curiosity and longing to satisfy the human need to know the cosmos that spawned us. Fancy that, a scientific movement that is justified on fundamentally spiritual grounds.

Mat Kaplan: Wow. David, I so look forward to you coming back. We can talk about SETI. We can talk about natural philosophy. We can talk about life, the universe and everything, but thank you for this conversation. And again, congratulations on being named a fellow of AAAS.

David Grinspoon: Well, thanks very much. It's a pleasure to talk with you and I'd be happy to come back anytime and talk about any of those topics.

Mat Kaplan: It is time for What's Up on Planetary Radio. Here's the chief scientist, that's Bruce Betts. He's going to tell us about the night sky and we'll have a contest and do some other fun stuff. Welcome back.

Bruce Betts: Hey, good to be back, Mat. Hi.

Mat Kaplan: Hi. I got off the ski jump okay, by the way.

Bruce Betts: I was so scared. It looked like such a bad wipe out.

Mat Kaplan: That was really fun. I've been playing that for people because it was just such a cute ending for last week's What's Up. We won't equal it today, but you'll equal it with whatever else you need to tell us.

Bruce Betts: Well, yes I will. For those of you hanging out in the pre-dawn, it's planet party central over in the east. We've got super bright Venus and below it, reddish Mars and on the morning of the 27th, the crescent moon will be hanging out with those. And if you've got a really clear view to the horizon, you can go to the lower left of those planets and there's Mercury and then yellowish Saturn. Mercury will get harder to see, Saturn will get easier as it rises up in the sky.

Bruce Betts: In the evening sky, it is planet-less. Still a fun place, lots of good stars. Of course, I will mention the constellation Orion. If you check out under Orion's belt is Orion's sword, what look like three stars, for those who aren't aware. The middle one is actually the Orion Nebula. It's fuzzy if you look at it, even with your eyes, and certainly with binoculars or a telescope.

Bruce Betts: This week in space history, it was 1966 that Gemini 9's primary crew of Bassett and See were tragically lost in a plane crash. But in happier news in 2007, after about a year-ish of travel, New Horizons flew by Jupiter and got cool data at Jupiter as it readied for its long journey to Pluto.

Mat Kaplan: I'd forgotten how quickly it got to Jupiter. I mean, really it set a solar system world speed record for getting to the outer planets, didn't it?

Bruce Betts: It did. And also for leaving the earth, but then Voyagers were trickier with their gravity assists and going for speed, so they're actually going faster at the equivalent distances these days. Anyway, that's dangerously blurring into a fact. So, instead let's give you a random space fact.

Bruce Betts: So the super massive ... super massive ... black hole at the center of the Milky Way galaxy is thought to have the mass equivalent to form four million suns. Bonus space fact, this is called Sagittarius A, written as an asterisk, and it was originally part of a radio source that got isolated. There was Sagittarius A and then Sagittarius A because one of the co-discovers, Robert Brown, said in a 1982 paper because the radio source was exciting, and excited states of atoms are denoted with asterisks.

Mat Kaplan: Ah, I had no idea. That's fascinating. And, 4 million sons? Yeah, I'd say that qualifies as super massive.

Bruce Betts: Yeah, so do I. But, hopefully that'll change. Let us move on to the trivia contest. I asked you what Olympic athletes appear in pictures on the Voyager Golden Record. How'd we do, Matt?

Mat Kaplan: People just loved this. Elijah Marshall in Australia, "Damn, Bruce. You guys weren't kidding when we called master of the rabbit hole. Where do you discover this stuff?"

Bruce Betts: Comes out of my freaky brain and then out of the internet and straight to your rabbit holes at home?

Mat Kaplan: Well, let's fill that rabbit hole. Here is ... He's back ... Our poet laureate, Dave Fairchild in Kansas. Olympic athletes, five in all, appear on Golden Records, riding out with Voyager. In analog, they're pictured Borzov, Roberts, Su Wen-Ho, all sprinting with Moorosi and working on the balance beam, a stroboscopic Rigby. Kathy Rigby. She's actually got several images, right? Because it's stroboscopic, you see her at different positions along this routine that she was doing on the balance beam. Very cool.

Bruce Betts: Indeed. Very cool. She counts as one athlete though, just to be clear.

Mat Kaplan: Okay, so five athletes. And, we have a winner. She has not won in just over two years, but she is a past winner. Courtney [Katz 00:00:58:44] in Pennsylvania provided Valerie Borzov, Motsapi Moorosi, Kathy Rigby, Edwin Roberts and Su Wen-Ho. And four of them, I guess all in one race?

Bruce Betts: Yes, all in the ... Of course, it was heat three of round one of the 1972 Olympic men's 200 meter race. And, the four captured running in that race and then Kathy Rigby, as you mentioned, on the balance beam.

Mat Kaplan: Courtney, congratulations. Once again, you are going to be getting a copy of this brand new book, Impact: How Rocks From Space Led to Life, Culture and Donkey Kong. And, it's by ... and it's hard to say what he does, meteorist, meteoriticist.

Bruce Betts: Meteoriticist.

Mat Kaplan: Oh, I like that. Thank you. Say it again.

Bruce Betts: Meteoriticist.

Mat Kaplan: Greg Brennecka. It's a fun book. I think I said before that he did some illustrations for it, little hand drawn illustrations, and it's about the significant role that media rights have played and continue to play in our life. So again, congratulations, Courtney. I sent you, Bruce, a copy of this wonderful letter that our listener, Norman [Kasun 01:00:01] in the UK actually wrote to the Olympics Study Center, which is part of the Olympic Foundation, and got an answer to this question from the research coordinator, someone named Estelle [Timfotey 01:00:17]. It's brilliant. Thank you for providing the letter, Norman, but you know, this was still missing Kathy Rigby in the separate image. So you'll have to go back to the Olympic Committee and complain.

Bruce Betts: It won't be the only complaint they're hearing these days.

Mat Kaplan: Ooh. That's true. Ooh, burn.

Bruce Betts: But, it was nice of them to do that and to respond so rapidly.

Mat Kaplan: Yeah, faster, higher, stronger. Together. A new and improved version of the Olympics motto.

Bruce Betts: Oh, I though that was Planetary Radio motto.

Mat Kaplan: Oh, it should be, shouldn't it?

Bruce Betts: Yeah, it makes so much sense.

Mat Kaplan: Here is Daniel Sorkin in New York. This question got me thinking about future off earth Olympics and what events might be possible in low gravity or micro gravity. That's one for you to think about, Bruce. I think there might be potential.

Bruce Betts: Oh my gosh. Before I came up with this one, that was a rabbit hole I went down and my brain started breaking when I was pondering the physics of ice skating and how it would change on Europa. And, I decided to move to something else, but I'll keep thinking.

Mat Kaplan: You know it's coming, right? Here is one other bit of poetry from Gene Lewin in Washington. Just one stanza ... we don't have time to read the whole thing, but it's a lovely poem. And here is the second stanza, four sprint 100 meters. One shows her strength and grace, with greetings from our planet home and sounds of the human race.

Bruce Betts: Oh, that's nice.

Mat Kaplan: Very nice. We're ready for another.

Bruce Betts: Well, you claimed that people wanted another math question. It's not complicated math, but you do need to combine research with math. We're going into Messier objects and Messier numbers, the deep sky objects that were first compiled by Charles Messier. And, here's your math question: what is the answer to the following math problem? First, take the number of objects published in Charles Messier's 1781 catalog. There's a lot of subtlety here, but it's the number of objects published and multiply that by the Messier number of the Trifid Nebula. Now subtract the Messier number of the Starfish Cluster, and that's what I'm looking for. Number of objects published in this catalog, Messier number of the Trifid Nebula multiplied, and then subtract off the Starfish Cluster Messier number.

Mat Kaplan: How do they enter?

Bruce Betts: Go to contest, or you can find it through the following mathematical algorithm ... Nah, I'm just kidding.

Mat Kaplan: Well, for the three of you who will enter this time ... No, prove me wrong. Prove me wrong because we're going to add to that algorithm a planetary society kick asteroid, rubber asteroid for anybody who works their way through that bit of math that has been handed to us by the chief scientist. That'll be coming your way, but you've only got until the 2nd. That'll be Wednesday, March 2nd at 8:00 AM pacific time to answer this one for us. Wow, okay. No, I'm glad you did this and we're done.

Bruce Betts: All right, everybody go out there, look up at the night sky and think about what Mat's Messier number might be. Thank you. Good night.

Mat Kaplan: It's a mess of Messier numbers. Extra points if you can identify which cartoon character I'm paraphrasing there. He's Bruce Betts. He's no cartoon character. He's the chief scientist of The Planetary Society. Nope ... who joins us every week here for What's Up.

Mat Kaplan: Planetary Radio is produced by The Planetary Society in Pasadena, California and is made possible by its lively members. You can add to evidence of intelligent life on earth by visiting Mark Hilverda, Jason Davis and Rae Paoletta, associate producers this week. Josh Doyle composed our theme, which is ranged and performed by Pieter Schlosser. Ad astra.