IRA FLATOW: This is Science Friday. I’m Ira Flatow. The time has come to close the book on Mars, literally. Of course, I’m talking about our book club discussing the search for life on the red planet. We’ve been reading The Sirens of Mars.

And back with me one more time is our own Mars Rover, Christie Taylor. Hey, Christie.

CHRISTIE TAYLOR: Hey, Ira.

IRA FLATOW: All right, all good things, as we know, must come to an end. And so what have we learned this month?

CHRISTIE TAYLOR: Yeah, Ira, we have learned a lot. We have considered how finding life that no one’s seen before may be harder to find than the kind of life we already have on Earth. We looked at the history and perhaps present of water on Mars. And we peered deep into meteorites, which are the only pieces of Mars that we can actually study in a lab.

IRA FLATOW: At least until we can send the mission to get samples back, right?

CHRISTIE TAYLOR: Right. Exactly, Ira. And we had one last Mars love fest last week. Listeners got a chance to ask planetary scientist and Sirens of Mars author, Sarah Stewart Johnson, all of their many questions in a live Q&A that we held on Zoom.

Co-hosting this Q&A with me was Stephanie Sendaula. She’s a Programming and Outreach Specialist for Library Link New Jersey and she recommended this book in the first place.

IRA FLATOW: So it’s all her fault.

CHRISTIE TAYLOR: Exactly. Stephanie and I started by going over some of what we had loved about reading Sirens of Mars, like how Mars has over the years been kind of a reflection of anxieties on Earth, from an astronomer who obsessed over it during the trauma of World War I to how climate change is perhaps motivating the current crop of billionaires to their sort of quest to colonize.

And then there’s the fact that the geology of Mars, unlike Earth, has remained mostly unchanged for billions of years. Here’s Stephanie talking about that.

STEPHANIE SENDAULA: Something that stuck with me, which Sarah talked about too, is how Mars is kind of frozen in time. So it’s just like this relic of the past. Just the concept of that, thinking about that, it’s just so fascinating to read about and want to learn more about.

CHRISTIE TAYLOR: And, Sarah, let’s talk about the story of our exploration of Mars, which is what you cover in this book so well. What were some of the major shifts of understanding that scientists had to have in order to get where we are today?

SARAH STEWART JOHNSON: We just started with this total blank slate. We just had this point of light in the sky. And even the ancients knew there was something really special and different about Mars. It wasn’t just its color.

But it had this crazy sort of retrograde motion where it would sort of every couple of years backpedal and go the different way against the rest of the background of the fixed stars. And it was a while before Mars was really understood as this world, like a place you could scrape your knee just like the Earth.

We start off with kind of amazing ideas of what this world might be. Because in 1965, it was the first time we ever saw the surface of another planet. And we get these images back and they’re covered in craters. And all the sudden there’s just this staggering disappointment that Mars is just like the lifeless moon.

And fortunately, we didn’t stop going to Mars. We kept sending these missions. And it’s sort of been climbing up from that kind of nadir ever since with all kinds of new discoveries that are just tantalizing and incredibly exciting, especially around the search for life, which of course is the piece of it that I’m most interested in.

STEPHANIE SENDAULA: Yeah, that’s such a great answer, Sarah, too. And I had a few questions, but I see a few people asking similar questions. Sarah, what do you think of the future of Mars exploration is? What do you think about billionaire interest in Mars colonization? Do you think it’s helpful in the long run or should we be concerned? I’d love to hear your thoughts about that.

SARAH STEWART JOHNSON: So when I think about the future of Mars exploration, it’s just this question of, will humans go to Mars? I do think that will happen. When will that happen? I really have no idea. It’s always been one of these things that’s been like 20 years away.

But I think that the stage is set for really rapid progress. There are huge technological challenges. The radiation environment’s incredibly punishing, long time space travel. The moon, you can get there quickly and get back, a couple of weeks. It’s a business trip.

But Mars, you are out deep, deep away. And if something happens, there’s nobody that can come rescue you. And so it’s just very hard. But I think that the sort of technological leap from when we had nothing, before Sputnik, to the Apollo program, that was 12 years.

And I think that the technological leap from where we’ve been with the moon to going to Mars, I think it’s smaller than that. So I think that if we decided we wanted to go, we could do it rapidly. It’s a tricky thing. And I feel kind of two minds about it. I think that there are ways that human exploration can go in tandem with robotic exploration.

But honestly, I spend a lot of time thinking about the next 10 years, the next 20 years, all the things that I really want to do with robotic exploration before humans arrive while we still have this kind of pristine planet. And there’s a lot of astrobiology and a lot of experiments that I’d love to see completed in the near term.

CHRISTIE TAYLOR: We have a question from Susan now. And she says, “I worked on a photosynthesis experiment that went on the first Mars lander.” And she says she wants to know what happened to it.

SARAH STEWART JOHNSON: Yeah, so what Susan’s talking about are these Viking landers that landed on Mars in the 1970s, first time we touched down on the surface of Mars. And there were these biology experiments, these three life detection experiments that were part of those missions, like both of those landers.

And all of these experiments taken together were sort of broadly interpreted as something was going on in that soil that was causing these sort of chemical reactions, but nothing that was indicative of life. And then the real kicker was there was also a chemistry experiment that was along for the ride that was a gas chromatograph mass spectrometer.

And it was looking for organic molecules, the kind of building blocks of life as we know it. And it found none, just none whatsoever. And it was so perplexing. Because how could you have life without the building blocks of life as we know it?

And it was years, decades, until we really understood what was going on with those signals, that there were these particular types of salts called perchlorates that were in the Martian soil. And it’s something I wrote about in the book.

And it’s almost like your dry cleaning the samples when you heat up the soil samples in combination with these really reactive oxychlorine salts. The signals can really disappear, kind of evanesce. And so that’s kind of where things ended up.

So we now have gone back to Mars. We’ve found all of those building blocks of life, all those organic molecules with the Curiosity Rover. So that was very exciting to definitively see those.

STEPHANIE SENDAULA: Thanks, Sarah. And that kind follows up a question from Kevin who asked, “what happened to the magnetic field? There is no more magnetic field at Mars.” So do you know what happened to it or do you have any insight on it?

SARAH STEWART JOHNSON: Early on, Mars did have a magnetic field. And so we get that from having a dynamo, from having convection in the core. And that’s why we have a protective magnetic field here on Earth, which we are very grateful for. Because it protects us from the solar wind. It protects us from having our entire atmosphere sort of sputtered away.

But on Mars, we think sometime around say 3.9 or 4 billion years, that early dynamo kind of shut down. And so Mars is this planet that’s smaller, have less heat of accretion. It may have just kind of gotten cold enough that that convection just sort of shut off.

But without that protective magnetic field, the thick atmosphere that we think was present on early Mars just began to be sputtered away to space. And that’s why now Mars has this very, very thin atmosphere.

CHRISTIE TAYLOR: We have another question from James who has another Mars science question about the poles of Mars. James, go ahead.

JAMES: Yeah, I understand that the Space Agency through some radar work found potential water under the poles. Are there any ideas about doing some drilling and sampling to see if it in fact is water in a liquid form and if anything living in it?

SARAH STEWART JOHNSON: Yeah, that’s a great question, James. And so there were these detections, these radar reflections that were picked up a couple of years ago in the south polar layered terrain, these under subglacial, briny, potential lakes.

And it’s so exciting to think about a body of liquid water that could be on the surface of Mars today, especially in the context of looking for extant life, or still living. But if this does get borne out that this is indeed an underground subglacial lake, we’ve done really interesting work like in Antarctica on subglacial lakes. And they are thriving microbial communities.

And I’ve been a big proponent of the idea of drilling on Mars, and getting down into the subsurface, and looking for traces of life, and potentially extant life as well. So we have the Rosalind Franklin Rover. It’s going to drill down two meters into that basaltic rock, not at the pole.

But we’ll at least get below a lot of that radiation damage at the very top of the surface. But then JPL, the Jet Propulsion Laboratory, has been working on some really exciting concepts for doing deep drilling. And maybe one day we could even drill as deep as those really exciting potential subglacial lakes.

STEPHANIE SENDAULA: Yeah, thanks, Sarah. And I think this kind of ties into what you were just saying earlier. What do you think Mars can teach us about Earth? That’s something I kept thinking about as I was reading the book. And there’s so much to learn from Mars and learn about ourselves in the process.

SARAH STEWART JOHNSON: Stephanie, I love question also. Mars really is all past. So much of the history of our planet has been lost because of erosion, because of plate tectonics. It’s almost like we’ve swallowed our deep geologic past plate by plate, and it’s gone.

There are just a few very small outcrops of really ancient rock. But on Mars, because, again, a lot of these geologic processes just slow down, and we don’t think there was potentially ever plate tectonics on Mars, we have just this incredibly perfectly preserved record.

And so what were the conditions like when life got started here even if there is no life on Mars? But then also understanding just kind of how these two planets that started off so very similarly– these are two planets that had thicker atmospheres, that were warm and wet, at least periodically. They had just very, very different paths.

And sort of understanding more about that I just think is really incredible and intriguing. And I think we can just learn so much about ourselves by studying Mars.

STEPHANIE SENDAULA: So your book was written before the Perseverance Rover was under construction. So what are you hoping it finds?

SARAH STEWART JOHNSON: So we probably won’t know for another decade or so. But the Perseverance Rover landed and now is in this campaign to collect all of these samples, about a couple dozen of those. And we’ll bring them back to Earth.

And it’ll take some effort. We’ve got to send a fetch rover. And then we’ll have a vehicle that’ll sort of bring them back home to Earth. And then we’ll sort of ferry them out to different laboratories.

My hope is that we can look into these samples and, again, find these traces of ancient life. And there’s a lot of other stuff that we’ll potentially find from these samples, kind of geochronology, understanding the timing and the history of Mars. There’s a lot of fundamental geology that we’ll discover no matter what.

But my hope is that there’s something like a smoking gun. And that we can take something that is really exciting and suggestive of life, that we can hit it with everything we’ve got, and we can build confidence that this is a real detection.

I still think about the Apollo samples that we brought back decades ago. We’re still learning the most extraordinary things from them. And once we have samples in hand, we’ll have them forever. And so the chance to study these as our technologies improve, as our techniques get better, I just think it’s going to be a tremendous opportunity.

CHRISTIE TAYLOR: Just a quick reminder, I’m Christie Taylor, and this is Science Friday from WNYC Studios, talking with Sirens of Mars author, Sarah Stewart Johnson, about all of your great questions about the red planet.

I’m so glad we’re talking about Perseverance. I believe Perseverance is currently bee lining for the river delta on Mars where all the magic is supposed to happen as we speak. And we have a question about that from Glenn in Florida. Go ahead, Glenn.

GLENN: I was just wondering why we designed this rover to get these samples, but not to bring them back. Why is there has to be a new mission to bring them back?

SARAH STEWART JOHNSON: Because it was so expensive. I mean, that’s the simple answer. The team that sort of came up with this concept– there are these planetary scientists that got together. And their motto was, “go big, and go home.” They even have little buttons and decals.

And this whole idea that once we collect these samples, it will be so compelling it will drive the idea of sample return. They got together and they said, this is the one most compelling thing we could do for planetary science, bring back really carefully selected samples of Mars.

And to do that, we’ve already spent a couple of billion just building this one rover. And there were a lot of constraints with that. It was built on the exact same chassis as Curiosity, again, to save money. We just didn’t have the budget to do it all at once.

And we’re hoping to get help from the Europeans, as well, in terms of bringing these samples back. But it really had to be in these three different steps to make it feasible.

CHRISTIE TAYLOR: Sarah, you are both the author of this beautiful book, but also a planetary scientist yourself. And we have a question about that from Shelby. Go ahead, Shelby.

SHELBY: My question was, what are your words of wisdom for future generations of students who are interested in pursuing a career in science and then even planetary science?

SARAH STEWART JOHNSON: Oh my words of wisdom, I still marvel at the fact that this is my job and that I get paid to do this amazing thing where I just wake up in the morning and I get to think about these huge deep questions, like is there life in our universe.

And I think studying things that you’re particularly passionate about, I think that’s really important. And planetary science, I mean it’s almost like doing Earth science 100 years ago. You can get up to speed on sort of what’s happening because there’s still so much we don’t know.

And it’s very interdisciplinary. It’s drawing from chemistry, from physics, from geomorphology, geophysics, all of these things. And biology, potentially astrobiology, is now becoming this big thing just in its own right. And I think finding some part of science and then thinking about how you can synthesize it with other parts of science is really helpful.

And really what we need is to sort of break down some of these traditional silos and bring together all of these different disciplines. Because places like Mars, they’re every bit as complex to understand as places like Earth. And we just really need a whole fleet of people working to help us.

CHRISTIE TAYLOR: And that’s all the time we have. I want to thank all of our listeners for their wonderful questions about Mars. And, Sarah, thank you so much, both for joining us and for writing this enthralling, poetic, detailed book. I feel like my perspective on the red planet has definitely changed quite a lot after reading it.

STEPHANIE SENDAULA: Thank you, Sarah. You were great.

SARAH STEWART JOHNSON: Oh, thank you both. This has been such an honor.

CHRISTIE TAYLOR: And, Stephanie, thank you so much for helping us be Mars nerds today and for recommending this book. It is, in many ways, all your fault.

STEPHANIE SENDAULA: Thank you so much for having me again.

CHRISTIE TAYLOR: Stephanie Sendaula is a Programming and Outreach Specialist for Library Link New Jersey. And Sarah Stewart Johnson is an Associate Professor of Planetary Science at Georgetown University and author of the book The Sirens of Mars. I’m Christie Taylor.

IRA FLATOW: Christie, another great book club. Thank you. What about people who want more of Mars?

CHRISTIE TAYLOR: Yeah, for anyone who wants to learn more about Mars or learn more about The Sirens of Mars, our website is still there, sciencefriday.com/bookclub. And from there, I always recommend people dip their toes into our online community. We’ve got some really thoughtful discussion happening there.

And of course, that’s the best place to stay informed about future book clubs and other treats for our SciFri bookworms.

IRA FLATOW: You said it, sciencefriday.com/bookclub. Got it. And thank you again, Christie.

CHRISTIE TAYLOR: Thank you, Ira.

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