Brian Keating

Searching for Alien Earths with Lisa Kaltenegger


Brian Keating:

Carl Sagan died over 25 years ago, but his legacy lives on, and so does the mystery that haunted him all of his life. What if Earth isn’t the only home for life in the universe? Imagine the vast expanse of space filled with planets teeming with life. As Karl said, if there’s no life, it’s an awful waste of space. But what does space look like? Could we even detect life on other planets? These aren’t just sci fi questions. They’re the heart of humanity’s oldest and most profound curiosities. And now, thanks to cutting edge technology and theoretical progress from today’s guest, we’re closer than ever to finding the answers.

Lisa Kaltenegger:

This is our first step. A biosphere that changes a planet and lets us spot life in the light that we collect with our

Brian Keating:

Under her leadership, a multidisciplinary team of scientists is developing innovative tools to detect signs of alien life. What exactly do we need for life to begin somewhere else? This is one of Lisa’s key driving questions, and her work propels us into these mysteries and beyond. She’s here today to take us on an extraordinary journey across the cosmology, seeking habitable planets and perhaps the next Earth, the alien Earth.

Lisa Kaltenegger:

But one of the things we don’t know is what condition do you need for life to get started.

Brian Keating:

Stay tuned as we embark on this cosmic voyage. You never know who or what we might meet out there. Welcome to an alien episode of the Into the Impossible podcast with a fan favorite, a personal favorite, and to my knowledge, the person who has done the most for spectroscopy since her countryman, Doppler. So Christian Doppler did a lot, and I think he would love to meet you, a fellow, Austrian. How are you doing today? I just talked about Christian Doppler this week, and I told my class, a cosmologist, I’m talking to you. So excited. Lisa, how are you?

Lisa Kaltenegger:

I am good. Thank you so much, and thanks for having me back on the show. I would love to be Doppler and especially, as you said, Austrian countrymen. Right? One of the things we would sit down with a great Austrian theory, like civilized people discussing science.

Brian Keating:

I always make, note that he was from the same town as another person who knew quite a bit about, frequency and pitch and melody, and that was, of course, Wolfgang Mozart. They were from the same town. So when I visited Austria for the first and only time, I made sure to pay equal attention and regard to Christian Doppler. So I should give your your your bio. You’ve been a a guest on the Into the Impossible podcast before, but you now have a book, and we’re so excited to talk about it. You are the founding director of the Carl Sagan Institute at Cornell University where I was almost born and almost got into, except I was rejected twice.

Lisa Kaltenegger:

But I said, the offer is open. Come and work for me, you know, any time. Yes.

Brian Keating:

I wanna do another post doc. The new science of finding toolkits to find life on faraway worlds, and this new book is about exactly that. And I think the thing that most is is just so delightful about you is you’re so authentic, Lisa. You don’t shy away from talking about challenges. You also don’t dwell on them. There’s there’s some aspects of the book where you talk about challenges of, you know, women and minorities and so forth, but you Arthur not by any means, you know, beholden to a class or a status and and you’re just your honesty is is so delightful. As a professional to another professional, I just I wanna congratulate you on that aspect, but the book is is a triumph. It’s one of my favorite new books.

Brian Keating:

Talk to me as we do. Help me judge the book by its cover. What’s the meaning of the title, the subtitle, and the beautiful artwork, which I only have, you know, half of the artwork, because you have another copy over there. Show me

Lisa Kaltenegger:

This is what I was was about to say, you know, you can actually take your pick. So you can have the British copy. And you’ve just shown the American copy. And the really interesting thing about this let me just bring it up here. I wrote a book. And then the publishers so Macmillan here at the US, that’s theory, and Penguin Press in the u in the UK. And I had no idea that you get 2 publishers for the same language, but you do. They made up their mind what this book is about, you know, and how they wanted to represent it. And so we’re going with the American first. So the title, I wanted the title to be Alien Earth because it has so much in it. It’s us searching for planets like ours around other stars, so alien Arthur. But it’s also I bring you into the history of our own planet because you need to understand the history of our own planet to be able to not miss signs of life if the planet’s just younger than ours or maybe older than ours.

And yesterday was pretty funny. I talked to my husband, and he was like, oh, alien earth, because you’re an alien in science sometimes as the only woman. I was like, oh, that’s a third aspect I hadn’t even considered that he took from that. And so I love the title.

Brian Keating:

superhero manic.

Lisa Kaltenegger:

Alien Earth. And then the new science of planet had to get the cosmos. Can I just tell you? It’s so funny because it’s alien Arthur. Right? But they have the science of planet hunting and the cosmos. Right? Planet hunting and the cosmos. The new science of planet hunting and the cosmos. So judging a book by its cover means you probably need both if you’re looking at this podcast. But

Brian Keating:

That’s right.

Lisa Kaltenegger:

What you see here is artwork from inside the book because I commissioned an Arthur, and she did an amazing job to an art.

It’s in black and white, but on the cover, they made it colorful. So all these very different worlds that we’re spotting in our cosmic horizon. And this, of course, on the US side is the gorgeous nebula and the picture from the James Webb Space Telescope, where we basically have stars and planets forming right now. So a stellar nursery, if you want, that shows you possibilities, places that could become like ours too.

Brian Keating:

And thinking speaking of possibilities, I can’t resist to quote the epigraph from chapter 6 entitled No Place Like Home. The limits of the possible can only be defined by going beyond them into the impossible. Lisa, you couldn’t you couldn’t have made me happier. You know? Yesterday, I talked to a, a gentleman named Nick Nick Bostrom, who’s a who’s a risk analyst in in Oxford. And, his press release had a had a mention of the podcast that he’s been on, including including, the Joe Rogan Experiment and the Lex Fridman podcast and Brian Keating’s Into the Impossible. So he won that, competition for best press release, but you have the best epigraph that I’ve ever read from my beloved Arthur C Clarke. But let’s get into what is possible and what’s impossible. When you and I were we graduate students, Clarke we undergraduates perhaps, it was even thought to be an impossibility that there could be other planets, let along habitable planets.

And I wanna ask you, how have your personal opinions or priors been updated? Do you think that there are aliens of a type that we could collaborate with, communicate with, and and play out the role that that seems to occur in science fiction? Or Arthur the aliens that you talk about in this book, the microscopic kinds that, you know, my toddler coughs up, on on occasion?

Lisa Kaltenegger:

So there’s a lot to unpack in there. So, I think what’s really interesting is that by looking at the Earth, we learn what he could look for. And so if you take the Earth at the 24 hour clock from when it was formed to now, About 5 AM in the morning is when we have signs that there was life on our planet, so 3,500,000,000 years ago. Around lunchtime, about 2000000000 years ago, you have the buildup of oxygen in the air that with a reducing gas tells you that a biosphere is changing the planet. And then a couple of seconds before midnight, you have you and me. So the question is, what do you strive to find, and where do you have the best chances? And so it seems to me that you have the best chances if you give it the widest time window that you can to find these other planets with life signs. And so that means I’m actually pretty agnostic between having, you know, a single cellular organism or having you and me or space dinosaurs, which definitely put space dinosaurs in here. But what that means is that this is our first step. A biosphere that changes the planet and lets us spot life in the light that we collect with our telescopes now, And then you’d need bigger and bigger telescope to make more inferences Keating us, like, do you also see technology gases that leave a smaller imprint in the air? Or do you even find a message? Or do you find a biopigment? So a color that indicates that this looks like, I don’t know, yellow algae or green plants.

And so it’s a puzzle piece step by step. And because you said, you know, when we were undergrads, there was no planets. I remember I started studying in 95. This is when they found theorists planet around a sun like star. And so it could have gone either way. It could have been 1,000 of years before we found theorists rocky world in this right distance around the star in theorists so called habitable zone. But we got so lucky, and this is why I wrote the book right now. Because with the launch of the James Webb Space Telescope, we have for the first time an instrument with a big enough mirror to collect enough light to not just find these more than 5,000 new worlds that we spotted, but to start to explore and characterize it by collecting the light fingerprint.

Brian Keating:

Hey there, fellow alien voyagers. I’m so thrilled you’re with me and Lisa today. We’re having so much fun. And I just wanna ask you a small favor. I found that only about 50% of you are subscribed to the podcast on YouTube or on audio podcast formats and I I don’t do this to make a living. I don’t charge anything for it. I merely want you to subscribe and share the podcast with your friends. So once you do that, just hit the subscribe button or follow the podcast and leave a like or a review or a rating wherever you can. Thanks. It really helps the podcast out a lot and allows me to to get great guests like Lisa and many more to come.

Brian Keating:

And when I think about your career, you’re kind of, exceptionally, responsible at many ways by, for the quantitative prediction of these biosignatures. And I thought, you know, we’d start I mentioned your connection to Christian Doppler and spectroscopy. Can you talk a little bit and don’t be afraid to be technical. I’ve got the brightest, most brilliant audience in the known universe. So don’t be afraid to be technical. Let’s talk about the nitty gritty details of you as an astronomer working with instrumentalists, working with analysts, and coming up with your own models and ideas.

What is the key enabling technology, the sine qua non that you and your team of brilliant scientists have been able to deploy and develop for the search for alien earths?

Lisa Kaltenegger:

So when you do science, you need a lot of people and a lot of ideas, and you need to put them together in a kind of a daisy chain. So one is the collection of light, what I just said with the James Webb Space Telescope. Then that light gets onto a detector, And there’s a lot of noise because the star is active. You know, when you think about the sun, they are like flares on the sun, the explosions, nothing bad, but it’s just normal. It’s a huge ball of gas that rotates differentially. So it’s not just one sphere. It’s just a lot of theory going on in a star. And, of course, in its core, the huge nuclear fusion.

So a star is incredibly complex and very fascinating. But so we got that. Then you have a planet that goes in front of it. Right? So the light of the star gets filtered through that air. But if you take a planet and if you just shrink it, like, take the earth and shrink it to the size of an apple, then the air where we’re trying to find the change that the biosphere did in gases is actually smaller or thinner than the peel of that apple. So the signal we’re trying to find is incredibly, incredibly difficult to spot, and the star keeps changing on a level stronger than that signal while we’re trying to find it. So you collect the light. That’s what the telescope does.

But then it goes on a detector. Then we develop a pipeline, and that’s not what we do in my team. We come a little bit later, and I’ll let you know once we start. But, basically, there’s a pipeline that looks at theorists light that tries to get rid of the noise from the detectors, from the telescope, from anything else. And then somebody looks at it and says, like, okay. What is planet and what is star? So that’s already a cleaned out signal that we get from spacecraft. And then we have to try to figure out which signals are now stellar and stellar contamination or stellar activity, and which signals can we say this is planet. And where we come in, so me and my team and the whole Carl Sagan Institute, I’ll explain why we need that desperately to make sense of what we see, is we come from the other side.

We basically say, okay. So what is this light fingerprint or the spectrum? I call it light fingerprint because that’s how I think about it, that every planet in our solar system has a different light that it reflects or emits from each other. So Venus looks different than the Earth, than Mars, than Jupiter, than Saturn. And so for me, the analogy with light fingerprint makes sense because the spectrum is unique so far for the planets we know. And so what we do is we actually do a modeling deep dive. Think about the weather forecast for tomorrow. So I have a climate model, but I changed the sun. Like, now I have a red sun in the sky because most of these worlds have been found around small red suns that are in the right distance.

And I figure out what that does to a planet like ours or to an earth at different stages of its evolution, you know, when it was younger, when life just started. And what I do is I then translate that in my computer to what my telescope would see. So you see, you have the data and you have the modeling from this side. And, you know, the ideal thing would would be if it’s a match. And so this way I go back to the database of light fingerprints because we make many of those. Because I don’t expect to be right the first time. But I hope we get close so we can figure out, what that signal means we’ll be seeing. And this is so my model is extremely complicated.

Right? So you have a planet, you have sources and sinks, meaning, like, life creates gases, geology, like, sucks up some gases, put some gases out, you have volcanoes, you have clouds, all of this. And this is where I need help. And this is why I big the Carl Sagan Institute here at Cornell, because what is all the diversity of biology? This is where the microbiology department comes in that I talk to and see what kind of life could there be under a red sun. What would they produce? Chemistry, geophysics. You know, what about if the planet is, like, way more active in volcanism? And so this daisy chain or this chain of trying to make sense of this light we collect, it goes deeper and deeper and deeper into what does it mean. And so this spectrum that we get, because light and matter interact and thus some of the light doesn’t make it to my telescope. This is I usually call it a stamp, like a stamp at a passport. The light that’s missing tells me, did the light encounter water vapor? Did it encounter oxygen? But what does it mean? And that means like, what what does this wriggle mean? Is it C o two? Is it oxygen? Is it water? And what are the possibilities? So that when I see something interesting, it’s like, no. No. No. It doesn’t look like us right now. Right? But observe 4 hours longer. And I can tell you if this is a huge volcanic planet that you look out for or if it’s an early earth. And so that’s how everything kind of

Brian Keating:

And I was curious because I’ve had on, many, many theorists, you know, but one was, Tim Palmer who shared the Nobel Prize for the IPCC on global climate change. He actually won the co co shared in the Peace Prize of all things even though he’s a physics. And his book is called The Primacy of Doubt. And that is a phrase from Richard Feynman, who spent some time at Cornell, by the way. And, and Feynman was, was an advocate of always doubting yourself and actually using doubt as a way to stimulate creativity. And I wonder when you make these models as as he does, Tim Palmer, on the climate, there’s inherent uncertainty. And in fact, he’s claimed that just for our own earth, we need to have a CERN level of of, advocacy and and, actually, hardware and software and people working at the $10,000,000,000 level, say. What do you say to people that say, Lisa, we can’t even model the climate, the atmosphere on Earth and the weather on Earth, you know, a week from now.

What hope do you have of modeling it on something on, you know, Trappist 1 or something that’s light years away, dozens of light years away? What do you say to such critics?

Lisa Kaltenegger:

Well, I theory, as you said, criticism is essential. It’s essential in science because the problem is if not, you get led to the what you want to find. And that’s one of the things that we learn as a scientist. So when we, you and your field, me and my, we find something interesting, the first thing we do is we throw all our doubt on it. And we assume we made a mistake, and we restart our computer. We do the analysis again and again and again because it’s hard to sometimes not interpret something the way that you wish it were. And so, absolutely, the good news I have for you is it’s a good and a bad news. Depends on how you see it. It’s basically those details that we worry about here with climate change on the earth that can make our life a living hell, like, if we cannot produce enough food and so on, they will not generate any discernible signatures in the light fingerprint of a planet. Like, as long as we’re not destroying everything. Right? That you could C. We actually have a paper on that. But how can you actually spot the death of bang earth? It’s not out yet, but we’re working on it. But what’s really interesting is that when a planet is very far away, you only see currently, even with the best telescopes we have, large amount of gases in the atmosphere or, like, substantial amount.

So if the amount of gas changes by about 10%, which is, like, huge. It’s a whooping 10% more c o two would be terrible for us, you and me, and for all the food production. Right? But in a planet’s fingerprint, that just will make the spectral feature a little bit broader. Right? So in a way, we are not good enough to find these small changes yet. And what I teach my students, another thing that I think is really important to help you, is to do a parameter exploration. So what I mean is I don’t model 1 planet. I talked about this database of spectral fingerprints of planets. I model many.

And the way that I do that is I always change the parameter, let’s say the distance to the star. I change it and I make it a bit cooler and a bit cooler and a bit cooler, and I run my modeling. And sometimes what can happen is you have a model and it does, you know, what roughly you would expect it to do, and then all of a sudden it does something else. And that tells you that the numerics in your model broke or that there is some problem that you really need to fix. But if you only would have modeled that planet in this one, you would have never figured it out. And so a parameter exploration helps you to figure out if the physics you have in your model is solid enough for what you’re trying to figure out. But even then, it’s only the best we can do. And especially if you wanted me to actually envision a completely different geology, a completely different life, this is where it becomes really, really hard to make any predictions because I don’t have any data to verify it against.

So we focus on our planet and its history until now because there we have data where we can verify how this would look to my telescope and so how I would be able to spot it. And then we keep the eyes open for anything.

Brian Keating:

So how sensitive are you to earth? You know, in previous conversations, I think you mentioned the earth is sort of like a Rosetta Stone. It has some, you know, outsized importance over some other piece of rock, you know, that we might find. Can you expand on how you use the Earth’s history but also are informed by the fact that there’s been many Earths. You you actually describe a multiplicity of Earths in this book. There wasn’t just one past history. So if we do see a planet, it’s, which could have life in the future, there might be no sign of it today. So to what are you sensitive to systematic errors, say, biases in only having n of 1 for any life whatsoever?

Lisa Kaltenegger:

Absolutely. N of 1. This is why we’re searching. I would like an n of 2, 3, 4, 5, you know, finding other planets in the universe that also show signs of life. But the really good thing is that our planet is 4,600,000,000 years old. And the way that I try to, think about this is if you had a time machine, what does not work?

You cannot get back in the past. I shouldn’t show that. But let’s assume you did have the Tardis. I would love the Tardis. Oh my god. I so would love to be on Doctor Who, Keating the TARDIS and be like the helpful science. You know? But if you were going back, I don’t think you would be able to actually identify our planet because, you know, continents move. You wouldn’t have any Himalaya or Alps anymore. You would not even have the same constellations in the sky anymore because those stars just happen to make a similar pattern in terms of brightness. But over 1000000000 of years, they move different directions in their paths in the cosmos. So if you landed on a young earth, and let’s assume you had an oxygen mask because there was no oxygen, so be careful, you wouldn’t be able to tell it apart from an alien planet. And so even though we have a sample of 1, and for life that is a problem because we have carbon based water based life sample of 1, our planet kind of can stand in for different kind of other earth, younger versions of it. That gives us a bit of a range of how long we can spot signs of life. And then what we do is we dive into diversity of life as we know it now and as it has been through the ages.

And we just had a paper out recently that’s called purple is the new green. And there we just picked out a biota, a burp purple bacteria that could live, in oxygenic experiment, so with oxygen or unoxygenic ones. And so then the question also comes up, well, maybe the earth was purple at one point. How will we know? And so just expanding creatively, but with a lot of scientific input from different fields, our search gets us a little bit away from n of 1 to be able to spot other n’s out there, hopefully.

Brian Keating:

I wanna take us on a trip through probability space, and and that really came through this, lovely illustration in, chapter chapter 2, how to build a habitable world. And your predecessor and the namesake of the institute that you founded and direct, Carl Sagan, once said, to make an apple pie, first, you have to make the universe. So this incredible illustration depicts all of cosmic history, not in 24 hours, but 13,800,000,000 years. And it starts off with, with the the, this is starting off with the big bang, and then it spirals out. There’s a cosmic dark ages, the CMB. Thank you, Lisa. Thank you. 

Lisa Kaltenegger:

You didn’t put Brian Keating as born

Brian Keating:

in 18/71. But anyway.

Lisa Kaltenegger:

You know, I I I didn’t wanna pander to it. Right?

You know, people will know this. They don’t have to hear you.

Brian Keating:

Everything spirals out and you’ve got Brian d, Trapp is 1, Alpha Centurion. It keeps spiraling up. And eventually, you get to theorists planets with, first plants on land, light ice age, Cambrian explosion, dinosaurs, the Himalayas form, Homo, and it keeps going. As you know, about a week ago now as we’re speaking in the end of April, there was a total solar eclipse visible from, not from San Diego sadly, but, nearby where you are. I don’t know. Did you see it?

Lisa Kaltenegger [00:25:27]:

Oh, absolutely. I went to Burlington, Vermont to the University of Vermont, and they had a 20% chance to have a clear day. So they invited me as a speaker in case we couldn’t see anything to actually have a little bit of an interesting entertainment. And we got so lucky. It was, like, clear, and it was gorgeous, and a


Lisa Kaltenegger [00:25:45]:

lot of people got sunburns. What is very unlikely, you know, in the


Lisa Kaltenegger [00:25:49]:

beginning of April, northeast?


Brian Keating [00:25:51]:

Yeah. You’re more likely to, you know, have a heart attack from too much Ben and Jerry’s there. But I I wanted I’m I’m a simple cosmologist. Right? I I build experiments, you know, I I turn wrenches and screws and, but if if I just took every one of these steps and I put, like, a one tenth of a percent chance of them happening, you know, that there’d be a, a a first planet, plant on land to occur. There’d be the late heavy bombardment, which reminds me theory remind people out there that, Lisa has her own asteroid named after her, Kaltenegger. What is it? 7734? Yep. Yep. 743? 134.


Brian Keating [00:26:30]:

Yes. Is actually a giant chunk of this, which is a meteorite, which which is, a version of of Lisa’s asteroid. I don’t have an asteroid, so I’m jealous. But this, can be yours if you have a dotedu email address. If you go to Brian, I will send one to you. And if not, try it try your luck. But, but Lisa, if I I by my simple calculations, if there wasn’t at least 3 different types of bombardments, the, initial bombardment of Theia which created the Moon from the Earth, by something that was like Mars, then we wouldn’t have the Moon. Many scientists believe the Moon is critical for plant life and and, and single cellular organisms to have evolved.


Brian Keating [00:27:10]:

Then later on, if we weren’t bombarded and and had the dinosaurs or sorry. Even before that, if we didn’t have cometary bombardment, right, we wouldn’t have had the oceans on on Arthur. Correct me if I’m making any, you know, freshman mistakes because I’m gonna be your student.


Lisa Kaltenegger [00:27:24]:

I’m more than happy to to talk about


Lisa Kaltenegger [00:27:25]:

it, but just keep going to the Arthur one and


Lisa Kaltenegger [00:27:27]:

then to get the decomposing.


Brian Keating [00:27:29]:

Extinction level event that took out the dinosaurs so that little rats and and varmints like, like those people at Dartmouth, you know, we I went to Brains, so and you’re at Cornell, so we we can make fun of or Harvard. Let’s say Harvard. The people at


Lisa Kaltenegger [00:27:43]:

Oh, oh, I work with people at Dartmouth and Harvard. Yeah. You know, you make fun of whatever you are.


Brian Keating [00:27:48]:

And then late last but not least, you know, if that didn’t happen, we wouldn’t so if any one of those events didn’t happen, we wouldn’t be here having this conversation about life. So my my always my supposition is there has to be some way to explain that, because or or to take into account that because if those are contingent features on which the existence of this call represents, then it seems to me very unlikely that there’s even single cellular life, let alone, you know, multicellular and and complex technological life like the woman named Cornell, formerly Cornell, now Arthur, Jill Tarter, who was at Cornell said, you know, it’s an awful, big waste of space. So so tell me, please, Liso, where where am I wrong if not in my supposition that life is extremely rare and earth is extremely rare.


Lisa Kaltenegger [00:28:35]:

So what’s really, really compelling about this, and this is, I think, why it is sticking so well, is this idea that sometimes we equate life with our evolutionary stage in us. So I’m not saying that I think it’s likely that another Lisa, another Brian, somewhere else will have a conversation similar to us. So that way, we are unique. I give you the uniqueness of the human species. I’m pretty sure that’s gonna happen because, you know, an impact that kills whatever other space dinosaurs there might be might or might not be happening. But I think it’s very misunderstood, and this is very, very normal because astronomers have been doing most of this. When you talk to biologists, they see life much more like you know, we usually see this beautiful tree of life, and that was a great way to actually make people understand that life evolves. Right? And so it stuck.


Lisa Kaltenegger [00:29:31]:

But it is actually a pretty bad analogy because the way that you if you talk to theorists is that life is much more like weeds. And depending on the conditions, then one of these life forms will succeed. And the conditions are just perfect for one wheat or for one, seedling for a theory, and that one becomes the dominant one. Maybe eats everything else or outcompetes everything else, like Darwinian evolution. But let’s uncouple this. Right? So now we’re at the stage where we had the the last experiment. So the bombardment then killed the dinosaurs. So if that’s not happened, there will be, other life that forms from after the dinosaurs.


Lisa Kaltenegger [00:30:09]:

And there’s a really interesting discussion going on that the oxygen level in a planet is actually not set. You can’t have more than 35% because then fires will never go out, but anywhere in between. And there’s an argument that maybe the dinosaurs were on the way out already because the oxygen started to drop in the atmosphere. So do we need an impact? I can tell you because we have a sample of 1, so I’m glad that we’re here. But let’s go further back. Once you look at life, on the earth, 75% of life doesn’t need light. So what that means is that you if you don’t have stable surface conditions, life’s gonna be okay. Because if it, for example, forms on the bottom of the ocean or its subsurface, it doesn’t care for stable conditions.


Lisa Kaltenegger [00:30:56]:

What that means, you don’t need a moon. And then if life actually gets to the surface of the planet without stable conditions, and theory, of course, winter is coming would be the phrase you wanna add here, then life should evolve for that. Life would actually have different capabilities than you and me. And the life we see around us because it didn’t have to evolve for kind of different conditions. It’s specialized perfectly for its niche that happens to be our planet. And when you go to other kind of niches like hot sulfur springs, life will have developed for that. If you take it out and put it on the normal surface, it’s not gonna be happy. If you put me into a hot sulfur spring, I’m not gonna be happy.


Lisa Kaltenegger [00:31:37]:

So life’s incredibly good to adapting. So now we have the second. So we have the the dinosaur bombardment. Right? Maybe not you and me, but life’s gonna be fine. And now we go to the moon that that the impact that formed the moon. So you don’t if you don’t need stable conditions on the surface, then you can live without a moon and without the impact of generating the moon. And now we go to the first one that is highly debated, very interesting, about where did the Earth’s water come from. And so the idea is that that was brought to the earth by impact, but with more and more understanding in each of these fields is developing so fast.


Lisa Kaltenegger [00:32:15]:

That’s why I formed the Carl Sagan Institute because I cannot keep up with the literature. Right? Because coming from university, I would have completely gone with the argument. Right? Like, it’s very unique. Life cannot. It’s very compelling in an argument. But so if you go to the really, really interesting side of geology, this is now this discussion whether or not they’re actually more than 10 oceans worth of water locked in the rock of the earth in the first place. Meaning that you don’t need the bombardment per se, that you could actually have it locked in the rocks that form the rocky planets initially. And this is why it’s really exciting because even so sometimes it’s very frustrating, but, you know, you have to throw out what you learned in university, most of it, or at least use it as a stepping stone, and then go talk to someone else.


Lisa Kaltenegger [00:33:01]:

And I find it fascinating that we can do that, that we can decompose it. And when we think about life as weeds, the probability seems to be you know, the numbers seem to be ever in our favor. But one of the things we don’t know is what condition do you need for life to get started. We know it adapts, but we don’t know if it can get started under different conditions. And so that’s the thing that we’re trying to work on in the lab, and that’s where the search becomes so important to try to figure out where we find it. A lot of times, it’s so fun, and it’s perfectly fine. I do the same, that they are in baked ideas on the bang. You know, where you’re like, oh, it has to be like us.


Lisa Kaltenegger [00:33:46]:

It’s like, no. It really doesn’t. It could be like a yellow space dinosaurs who is talking in a podcast and saying, oh, I wonder what these earthlings are. I wish they stopped


Brian Keating [00:33:55]:

talking about us. There’s a concept mentioned in the book called panspermia which I always say sounds dirty but it’s not. I think it was either coined or popularized by Fred Hoyle who also coined the term big bang as a as a term of disparagement for the origin of the universe, which you also talk about in the book. Talk about the following challenge that I’m gonna present to you. The fact that we don’t observe life on Mars, can that not be said to limit the biologist Clarke that you said that life is like a weed? In other words, the fact that Mars rocks have landed on the Earth, as you talk about in the book, and I actually have a tiny sliver. I actually gave a tiny sliver to Joe Rogan, if you can believe it, and I I think he smoked it. I’m not sure what he did, but I’m not sure. Joe, tell me what you did with that moon the Mars rock.


Brian Keating [00:34:43]:

But tell me, the fact that we don’t observe life, there’s no historical record. Now, yes, we haven’t checked all of Mars and and so forth. So there’s some caveats. But am I wrong? Couldn’t the nonobservance of life right now limit how actually efficient panspermia is to spread life once it arises? Not solving the origin of life, but can we not say that, you know, life in the universe might not be as abundant as those biologists think because we don’t see any on Mars and you would expect that a binary planet system that has exchanged material for 4000000000 years should have some contact biologically. So where am I wrong there?


Lisa Kaltenegger [00:35:22]:

It’s a great, great question, and it has been, active debate in research for the last couple of years. And what they came down to is that you actually life’s really good to adapt, but you have to give it its environment where it strives to give it a chance to adapt. So you don’t just have to bring life to another planet. You actually have to bring enough of its environment to another planet for it to be able to evolve and adapt to the new conditions. So currently, if you have, like, let’s say, an asteroid, right, that brings the material to Mars and then hits Mars, you immediately have no water, and you have no atmosphere. Right? And so that is a huge change from the conditions you have on the earth. And so even from the conditions you had on the early earth. So I’m not so worried about that not having a panspermia tells us something about the prevalence of life.


Lisa Kaltenegger [00:36:20]:

I’m more, wondering about the different moons in our solar system where we have hopes that the liquid water under the icy, icy surface of Europa Enceladus or the cool moon of Titan could harbor a second genesis. If we found life somewhere else, let’s say, in the depths of Mars, right, this is why all the new missions now have something to dig and trying to to look at the theory, or under the ice layers in Europa on Enceladus or on Titan with the new dragonfly mission that we’re sending. If we’d had life twice in our solar system, and it looked different it’s a key point. And it looked different. So it wasn’t panspermia. It’s actually life that arose again. Then it must be everywhere in the universe if we get 2. If we don’t get 2, that doesn’t mean it’s not everywhere in the universe.


Lisa Kaltenegger [00:37:10]:

But I do think panspermia has this edit problem now that you not just have to bring the life, but also enough of its environment to get it to the point where it can evolve for new environments. And the way that I usually say this in class, if I take my basil plant that’s that’s not as healthy even on


Brian Keating [00:37:29]:

my Ethoca.


Lisa Kaltenegger [00:37:30]:

Window. You know? Yeah. I know. It’s just tropical. We’re talking winter. Uh-huh. Yes. I know.


Lisa Kaltenegger [00:37:34]:

But it’s just like, if I would take it and I would plop it


Lisa Kaltenegger [00:37:37]:

on Mars, it would not have a chance, you know, evolution or not.


Lisa Kaltenegger [00:37:41]:

And so even single cell and


Lisa Kaltenegger [00:37:42]:

our organisms are incredibly complex. We think of it being basic, but they’re really not. They’re doing a lot of amazing things and, like, dropping them in a completely different environment without the nutrients they need and without a without the chemical gradient that they accustomed to is gonna be a shock. And so most of


Brian Keating [00:38:01]:

them will make them wonderful turns of phrase in the book, but, yeah, one of them is about proof of life and what would constitute proof of life. Again, we’re not talking about, you know, brilliant, you know, Ivy League professors like you and and discovering them, but just finding life. And you focus primarily on oxygen and methane. And I think a good, a good question for you to tackle might be the fact that there was life that produced that oxygen. So if you looked at an early Earth, at least again, I’m sorry to be so, so geocentric as as, you know, Copernicus warned us against doing. But nevertheless, Lisa, we only have Antebuan right now. So but tell me, if you had looked at that planet, you would you have concluded that, no, there’s no life there even though it would eventually turn into the Earth as we know it, Keating with you and me. And it was actually anaerobic bacteria that were doing their job to make the oxygen that we know and appreciate and love.


Lisa Kaltenegger [00:38:57]:

Absolutely. So we are incredibly conservative in our search, And we’re incredibly conservative because extraordinary claims require extraordinary evidence. Right? Sitting in Carlos O’Sagan’s office right now, I have to do this. Yeah. I can’t wait for you


Brian Keating [00:39:15]:

to have your own puppet.


Lisa Kaltenegger [00:39:16]:

The interesting thing is that if you say that you found life, you want to be sure that you have no other explanation than for life. And when we go back to the 24 hour clock of the earth, right, we said at 5 AM, life starts, but only at lunchtime, 2000000000 years ago, actually builds up oxygen with methane. And even then, there wasn’t so much oxygen starting out, so it’s harder and harder to spot the further you go back in time. But before, it produced mostly C o two and methane. And I can get that out of volcanoes, So I won’t be able to tell and just go back, you know, to the idea of methane on Mars. It is life. Is it not life? If I have an explanation that doesn’t require life, then I can’t consider it as an extraordinary evidence. And so we are incredibly conservative in our search.


Lisa Kaltenegger [00:40:10]:

I completely agree with you. There’s gonna be a lot of life we will miss. But there, we have the statistics in our favor because we figured out that one out of 5 stars, that’s what the Kepler mission did for us, by looking at a 150,000 stars and trying to get the frequency of how many planet per Arthur. 1 out of 5 stars has a planet that’s small enough to be a rock, so below 2 earth’s radio, and at the right science, so not too hot, too close to the star, or not too cold in the habitable zone. And then of course we know that there are 200,000,000,000 stars roughly in our galaxy alone, and then billions of galaxies. So we kind of have Keating in Carl Sagan’s office. So having to say theory are 1,000,000,000 of 1,000,000,000 of possibilities even in our Milky Way alone. And so even though we’re gonna miss a lot of life, remember at least half of this 24 hour Clarke, we have new signs that are unique.


Lisa Kaltenegger [00:41:09]:

So if you have enough options, hopefully, you will still spot some.


Brian Keating [00:41:16]:

Would you actually like to own a piece of the early cosmos? This is a meteorite, a 4000000000 year old fragment of the early solar system, and it could be yours if you’re the lucky winner in this month’s drawing of my subscribers to my Monday magic mailing list where I send out something amusing over, an appearance that I’ve been on or been featured in recently, something genius, something imaginative and inspirational, an image that astounds and delights, and a conversation just like this one that I share with all the listeners. So join over 10,500 subscribers to my Monday Magic mailing list and you might win one of these meteorites. Go to Brian And if you’re a student and you have a dotedu email address in the US, you’ll automatically win a meteorite. You, talk about the catalog of our solar systems and and not only the major planets, but their moons. And I I thought it was, kind of delightful. Recently, I read a quote that Johannes Kepler speculated that, that Jupiter had so many moons, 4 at the time, because it was lonely. I I think I might have heard that from your fellow your coauthor, Marcela Gleiser, whose episode I recorded a while before this, but yours is gonna come out first because, anyway, you’re a 2 2 time gasket priority on the end of the impossible part.


Lisa Kaltenegger [00:42:31]:

Please do.


Brian Keating [00:42:32]:

But talk about the role of moons and and where life might be hiding close to home and and these beautiful stunning images from Webb of Titan and and and the the moons in our solar system, might they have life?


Lisa Kaltenegger [00:42:45]:

Absolutely. And so the really fascinating thing is, like, I said 1 out of 5 and billions of possibilities. Right? But I’m not even counting any rocky moons around gas giants that could, in addition and here we go into Avatar and Pandora. Right? Science fiction is actually showing us, helping us, imagine this, provide other boats or abodes of life. So I’m not even talking about that because actually characterizing your mood is even so much harder than a planet around another star. But when you can get to it, and now this gets us to our solar system, it becomes much more interesting because even though there is no biosphere that changes the whole moon in our solar system. And when you do theorists search around other stars that are so far away, the biosphere needs to change either the surface or the gas, the air on that planet, for me to spot it in the light that I collect. We talked about this before.


Lisa Kaltenegger [00:43:43]:

But in our solar system, for even for these really, really interesting places, it doesn’t. Right? So if you have an ice layer around Europa and Enceladus, in a subsurface ocean where we hope there could be life, and so we’re sending missions to investigate that. But because we’re sending it, and currently we can’t, but we will in the future, we could land and actually drill a hole in the ice or fly through the plumes of these geysers on the surface of these icy moons to analyze specifically if they’re Clarke broken pieces of DNA or a cell structure or something that we can only explain with life. And, of course, what’s really cool is we’re sending a quadcopter to Titan, where it’s basically gonna land, get a sample, analyze it, go somewhere else, land, get a sample, analyze it. And if I would love the search for life in space, I would love to be like the


Lisa Kaltenegger [00:44:36]:

person who flies the quad kept on Titan. You’re like, you know, just flying like, oh, I kept on Titan. I see that we have such a cool job.


Brian Keating [00:44:43]:

It was good to put on my pilot’s license.


Lisa Kaltenegger [00:44:46]:

Here you go.


Lisa Kaltenegger [00:44:46]:

You are actually closed. You should try to figure out and see if you can do that.


Brian Keating [00:44:50]:

So let’s talk about the, the the paper that you wrote with, Marcelo and, I think it’s his student, Sarah Vanna. Yeah. So what what is information theory and in what sense can it help to identify signs of life on planets as they brains, like, make, it, like, giant annular eclipses around their host stars? What what way can information theory, after you define it, can it aid the search for extraterrestrial life?


Lisa Kaltenegger [00:45:20]:

So the way I see it is the artificial intelligence machine learning, you know, allows us to actually scout through data or to analyze data much more effectively. And so we have been starting to explore different algorithms in machine learning that could, if you give it a spectrum, so the reflected light from a planet, take it apart into, oh, there’s some green plants, or there’s some sand, there’s some oceans, there’s some clouds. Right? And even so, I can do it with my eyes, or I have the hardest time trying to figure it out with a normal, you know, algorithm. Machine learning, you can train fast, and it doesn’t matter if you give it, like, a 100 different surfaces. It will just check what makes the most sense. Right? Which combination would actually if you train it. And now we have the computer power, so we generated, like, 300 1,000 different kind of planet models and let it train on it to see how see how good the algorithms would be to retrieve different surfaces. And now add to this what we do in language.


Lisa Kaltenegger [00:46:26]:

Because, you know, we have machine learning algorithms that have, like, a specific task and there are specific algorithms that everybody uses in the different fields. But we have also language, which is pretty complex. And so this kind of using the tools that already exist for different fields and now feeding it into the analysis of this data was where Sarah led this, amazing paper with Marcello, where she basically took the models that I made for the earth through time and said, so could I use these algorithms? Most of these methods that have been developed for for something completely different to actually spot biosignatures. And maybe they Clarke even more helpful because they were developed for something very different, but the way that they approach information is not unique, but it’s theory, very effective trying to get all the information pieces together to get a result. So if you apply that to Spectra, you get actually quite amazing results. And some of the things that we learned, what was very interesting because nobody knew before, is, of course, the star makes a big difference, right, in how the spectra look like. Makes science? Red light coming in or yellow light coming in, getting reflected is different. And so Sarah explored that, and we basically figured out what kind of template you’d need to use to guide the search.


Lisa Kaltenegger [00:47:52]:

And that was the first step. And now we are happily discussing other, language models and other models that we could use and kind of it’s not misappropriate that we can appropriate for this search even so they were never ever done for it, but they have tools that we haven’t So


Brian Keating [00:48:09]:

here at Public University in California, these Clarke spectrometers, so we might find one of these beautiful purple planets like you talked about before. So I have a few more questions if you’ll if you’ll beg my, pardon my indulgence and and my request of you. They said it’s just too much fun to keep talking about it. I wonder if we could, you know, sort of start to wind up by talking about the philosophical, the societal implications of discovering extraterrestrial life. First of all, there are claims right now by government agencies, by scientists that not only have we detected life, but they’re visiting Earth and they have technology. What do you make of these theory, these claims by people like, David Grush, that we’ve discovered nonhuman biologics? How do you react to those, claims that have been, made recently?


Lisa Kaltenegger [00:48:56]:

I so wish they were true because they would make the search so


Lisa Kaltenegger [00:48:59]:

much easier if if somebody was coming or we had none, you know, none,


Lisa Kaltenegger [00:49:05]:

Earth like biota. Great. Because it’s really hard to envision it and also to get the data to figure out that this is the right way to go with non earth biology. But the problem is that that data is always kind of out of context, and a lot of it is, like, bad data that you cannot verify. And a lot of it is just not it doesn’t hold up under scrutiny. This is what we were talking about before. Right? You have to throw all the criticism at it. And, unfortunately, none of it holds up.


Lisa Kaltenegger [00:49:35]:

And there’s there’s now agreements, like in NASA looking at this and trying to figure out what it is. But there’s a lot of stuff we also some of it is easily dismissed. But some of the other theory, like, for example, weird weather phenomenon that makes something look like there’s a reflection that’s not there. Right? All of this is really, really time consuming to get to and to explain otherwise. And most scientists have other things to do, you know, that that they really wanna do something else and not debunk this. And so this is why there was a lot of vacuum, I would say. And that allowed some voices to grow very loud that wished that it was true. Right? I wish it was true too, but, unfortunately, I’m trained in scientific methodology.


Lisa Kaltenegger [00:50:18]:

So, unfortunately, no. Not yet. I can’t say I cannot just claim it. You know, I wish I could, but no. So we haven’t found life outside of our solar system yet. And what’s kind of interesting here, and I think that might be where you’re going with this, what’s kind of really interesting thing here is if we have billions of possibilities, right, of planets that could be like ours, then it falls back to this question, is this eerie silence scary? Right? Why has nobody talked to us? Why has nobody come? Is everybody dead, or did they never start? Right? And this is where your question come in, and this is why it sounds so logical that it must be hard to get life evolved to a certain stage. Right? Because if this impact didn’t happen or that impact didn’t happen, it would be very different here on earth. But when you look at this question, and that’s what I what I did in the book, and it it’s a very private interpretation of it.


Lisa Kaltenegger [00:51:13]:

But I’m like, if there were lots of interesting worlds out theory. Right? And I tend to ask my students. I’m like, what after classes, I always ask is, like, okay. So we have 2 planets, hypothetical, that show signs of life. 1 is 5000 years older. 1 is 5000 years younger than us. Which one do you want me to go to? And reliably, it’s the more advanced one, except if they’ve seen the 3 body problem. That actually made a really statistical change in my or read the 3 body problem.


Lisa Kaltenegger [00:51:44]:

It’s really interesting because some people now got scared. But for those people, don’t worry. The distances have asked, and it would be very stupid for an advanced civilization to land on an inhabited planet no matter what Star Wars or Star Trek do. Because just think about vaccines. Think about war of the worlds. Right? What’s gonna get you is the viruses that you know nothing about if you’re also carbon based. So you’d rather go to a planet that has no life, so I don’t worry so much about that scenario. But reliably, they take the more advanced one.


Lisa Kaltenegger [00:52:16]:

And then if you turn it around, why would you call us? You know, we are just starting to get to the exploration at at this edge of looking out and trying to find life in the universe. We have boots on the moons, but we didn’t have boots on we don’t have boots on Mars yet. Right? We have rovers, but and bang helicopter. But we don’t have boots on Mars yet. So why would you wanna call us? And so this whole concept of whether we’re alone, to me, it’s a gorgeous connection for us with the cosmos because the earth is not a globe that’s, like, beautifully protected under some kind of, I don’t know, glass thing. But we are part of the cosmos through and through. That means we should understand our environment. And one of the parts is we should understand how our planet works.


Lisa Kaltenegger [00:53:07]:

And the best way we can do this is by finding many planets like it to figure out how an Earth really works.


Brian Keating [00:53:14]:

Oh, Lisa, this has been tremendously enjoyable for me as I knew it would be. Doctor professor Lisa Kaltenegger is an award winning astrophysicist and astrobiologist and the founding director of the Carl Sagan Institute at Cornell. She’s a pioneer and world expert in modeling habitable worlds, They’re light fingerprints and has spent the last decade trying to spot new ways of finding life in the cosmos, NASA and ESA, and many other of her collaborators and teammates. I can’t resist asking you because one one thing theory always resonates when I think about you is that you’re an educator, not just of the public, but also of your students. How has education changed? How has being a professor changed since you started, you know, a little while ago. How’s it changed? What do you see as the future of our profession? You know, it’s a 1000 years old. I call it the 2nd oldest profession after you know what. But, how has it changed, you know, and what what, yeah.


Brian Keating [00:54:11]:

Sure. But how’s it changed and and what do you make of the prospects for us? Are we still going to have, you know, cushy jobs Brian, you know, will theory still be relevant in 21100, you know, for our future and your granddaughters and our our professors, Lisa? What do you think of the future of academia as a professor? To me, my personal philosophy


Lisa Kaltenegger [00:54:31]:

about teaching is to teach students the way I see the world. And what that means is, everything I’ve read, every experiment I run, everything I’ve done, everything I’ve read, every experiment I run, everything I’ve done informs how I see the world. And so this is how I think as an educator, and this is what I was trying to pack into the book. This is how I can teach effectively because you don’t have to read all the papers I write. You don’t have to do all the experiments I did, but I’ll show you how all of that combined to how I see the world now. And if you approach teaching like that, then there is no other thing that gives you that, but a person who actually has this experience and wants to share it. I am actually really excited about the artificial intelligence tools that we’re developing right now because, as I said before, there is too much information. What’s a good thing? There sometimes people say, like, oh, the good old times of Renaissance scientists where one person knew everything.


Lisa Kaltenegger [00:55:32]:

It’s like, yeah, because there wasn’t so much to know. Right? I’m not dissing any of the amazing scientists from that time. It’s just it is just not possible right now to do it anymore, and it’s even hard to do it for your field, let alone many different fields. Again, this is why I big the Carl Sagan Institute. But I want to use this artificial intelligence to help my students curate that information, but intelligently. Because there’s so much information and some of it is really bang. And you need to be able to tell the difference. That’s gonna be the next I think we’re gonna have to put much, much more emphasis as teachers onto how to vet information, how to figure out if this is reliable or not, and how to ask smart question of where it comes from, you know, try to find a secondary source, things like that.


Lisa Kaltenegger [00:56:20]:

And in that sense, I think teachers and mentors, whatever you wanna call us, you know, we’re professors and teachers. But in a way, we are mentors to to let you figure out how to understand the world around you. And I hope when I teach, I don’t just teach my students about the cosmos and their place in it. I teach my students of how to best access the information around them and use them, like, you know, the best way they bang, but also responsibly. And so in that sense, I see things like AI that a lot of times will say, like, oh, it’s gonna replace teaching. It is all that information, but it needs to get curated. And I love it because, you know, I tell my students, use this. Right? And I experiment something.


Lisa Kaltenegger [00:57:06]:

But, you know, maybe my student doesn’t wanna raise their hand and say, I really didn’t understand the 3rd time you explained it. It can go to AI or, let’s say, chat CPT or something else. It’s like, explain it like an 8 year for an 8 year old. Explain this concept for a 13 year old. Explain this concept for an 18 years old. And so they can actually go up themselves. And I take this prerogative for myself too. If there’s something I


Lisa Kaltenegger [00:57:28]:

don’t understand in another field, it’s like Claim


Brian Keating [00:57:30]:

it like I’m the director of the Carl Sagan Institute.


Lisa Kaltenegger [00:57:32]:

Yes. Intelligence school. Oh my god. And theorists so okay. Let me see.


Brian Keating [00:57:38]:

Well, it’s such a delight. Your writing style is just like your conversational style. It’s delightful. It’s informative. It’s educational, and it’s inspiring. And I know my audience is gonna love this book as they as much as I did, I listened to it. I read it in digital and paper form. I wanna thank you so much, Lisa, for your gift of this wonderful new book.


Lisa Kaltenegger [00:57:57]:

Thank you so much, and thanks for the kind words. When you write a book, the one thing that’s so amazing is when people actually take something from it, and then you hear that he did it and they enjoyed it. So thank you so much for saying that.


Brian Keating [00:58:10]:

Absolutely. Thank you so much, Lisa. If you made it all the way to the end, I know you’re a cosmic enthusiast and you’re well equipped to explore the cosmos. Don’t miss this episode as theorists explores the universe for more alien goodness. Tune in next week for more of Into the Impossible.

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