good morning good afternoon good evening wherever you are on this planet or somewhere in orbit or on earth welcome to our city life my name is frank marches i'm an astronomer at the city institute and director of citizen science for unistella as well so today we are going to have a discussion about how we can use greenhouse gases to detect technosignatures or civilization living on another planet, an exoplanet.
And for this, I invited two people who have published a quarter of a paper that was published recently in Astrophysical Journal. So let me just say hi to them. Hello. Hi, Eddie. How are you? Great. Thanks. Hi, Daniel. So, Eddie, where are you calling us from? I'm calling you from Riverside, California. I'm in the Department of Earth and Planetary Sciences at UC Riverside.
Okay, you're assistant professor over there, and I saw in your bio that you're interested in observation of Earth as an exoplanet, climate, photochemical, radiative transfer modeling, et cetera, et cetera. So that's perfect. And you're the first author of this paper entitled Artificial Greenhouse Gases as Exoplanet Technosignatures. So welcome, Eddy. So your name is Eddy Swisterman. Yeah, trying, trying. Hello, Daniel. How are you? I'm good. How are you? Good to speak to you.
Good to speak to you, too. It's been a while. You are in Switzerland right now. Yes, I'm in Bern, Switzerland at the moment. I was just swimming in the river outside and came back. Always a fun life, always. So you're an astrophysicist and astrobiologist at ETH Zurich. You're a communicator. You've been working with SETI Institute in the past at the Frontier Development Lab and other projects. And I have a question for you because I look at your bio and I have a question. What is CEPAC-TACRO?
Yes, when I was younger. I actually still play. It's a foot volleyball game that is very popular in Southeast Asia, actually. So in Thailand, Malaysia, it's one of the top one or two sports. And I actually used to be on the German national team, not because I'm so good, just because there's not so many people playing it. played on a couple of world championships over there and in Asia. So it's not yet an Olympic game, right? No, we actually tried. We are trying to get more countries involved.
So if anyone is watching there from a country that doesn't have a Sepak Takra Association yet, start doing it and you might get Olympic. Yes. Okay. So that's a message for all our viewers. Please let us know where you are watching us from. And Eddy, So you wrote a paper which has been around. I mean, I read so many press release articles about it. I'm kind of curious. So what do you tell people when they say that and asking you about you search for ET?
What's the reaction they have about the fact that they know someone who is searching for ET on exoplanets? Yeah, well, I think most people don't think we're alone in the universe and think it's worthwhile to search for life elsewhere. And so, yeah, I mean, I think people are just generally very interested in it. And I just have to stop myself from talking too much about it. Okay. Well, we're going to be talking about it for 30 minutes. And let me say hi to our viewers.
We have people watching us from... Jacksonville, Florida, India. Two people from India. Say your city next time because India is such a huge country. Germany, Poland. Welcome. We are going to talk about the detection of greenhouse gases for technosignatures. Okay, so let's go back a bit to the science. One of the motivations of your paper that I read last night is basically that you are trying to find signatures of terraformations of exoplanets.
So before we go into the details, could you please, Eddy, tell us why do you think that aliens will be terraforming the planet and what exactly you mean by terraformation? Yeah, so we kind of mean modify the planet's climate is ultimately what we mean.
Even though terraforming literally means make like Earth, we figure that because humans have proposed to terraform Mars, make it more amenable to habitation by humans, ET may think an otherwise uninhabitable planet in their system could be amenable if its climate were modified. If it were too cold, you might want to heat it up. Another reason is... Your planet, because of, say, Milankovitch cycles, tilt of the axis, may be getting very cold, entering into a glacial cycle.
And so you may want to heat the planet up to prevent an ice age. And there would be a reason to maintain that situation for a long time versus, say, pollutant gases, which could have a deleterious impact on a civilization. Okay. So... We have plans to terraform planets here. Daniel, you mentioned that there is some discussion about terraforming Mars. Is that something doable? I'm not an expert on terraforming, but I think in principle it's physically possible.
It probably takes literally geological timescales, so it's not something that you can do in a decade or something like that. But as I already said in the press release, I think it's also very cool just a thought experiment to do it.
First of all, because we might be doing it, but also as a good test for things that we could actually see how okay so that's a good transition so we don't we see from far away a planet i mean let's assume we see it we have instruments that do that we're going to go into details what about the instrumentation but let's talk about the the physical process what kind of signatures do we expect for a planet being terraformed So a planet being terraformed, what you have to do is you
have to adjust the rate of balance of the planet's atmosphere. So in other words, if the planet's too cold, you want to put greenhouse gases into the atmosphere that absorbs infrared light and scatter some of it back to the surface, thereby warming it up. On Earth, too much greenhouse gases is bad because we're changing the climate on a very rapid timescale. But you could imagine intentionally doing this for a planet that's otherwise uninhabitable.
You'd be looking for the signatures of those specific gases that you'd be using in order to heat the planet up. So are we expecting to see those aliens putting some water and carbon dioxide into the atmosphere of the planet? Is that the kind of signature we would expect to see? So water and carbon dioxide are very common molecules in the universe, and they're common on Earth. And they're also not actually the best greenhouse gases.
So the best greenhouse gases actually absorb over a wider range of wavelengths or types of infrared radiation. And they're not common. So we're less likely to mistake them for normal geological processes. All right, so can you give us the names of those more complex molecules you are looking for? Who wants to volunteer and describe some of them? I think Eddie is the expert. If Daniel doesn't want to, I can start.
So we looked at five specific gases, carbon tetrafluoride, which is CF4, hexafluoroethane, which is C2H6, octafluoropropane, which is C3F8, sulfur hexafluoride, which is SF6, and nitrogen trifluoride, which is NF3. Okay. So those are molecules which are kind of complex. I mean, based on what you described, there is like multiple atoms in them. You can Google them to see the kind of geometry of those molecules.
And the effect is that if you put them in an atmosphere, they will basically act as a blanket and increase basically the temperature on the surface of the planet. Is that a good summary? Exactly. So they are really, really strong absorbers. So 1,000, 10,000 times stronger greenhouse gases than even methane or CO2 that we have here on Earth. And they are really... Their sources can, as far as we know, at least only be industrial.
So there's... to the best of our knowledge, no natural process or even like biological process that produces these gases in amounts that are needed to really change a global atmosphere. So this is why we think it's also a good technosignature, not just a biosignature, but really something that needs the involvement of technology to produce these atmospheres.
OK, so if you look at those planets, from far away from different techniques and you detect those molecules, you will say, Eddy, that those molecules are the signature of technosignatures because there is no natural way to produce them. So there's very slight abiotic sources from weathering of fluorite minerals for carbon tetrafluoride and sulfur hexafluoride.
And that results in, at best, parts per trillion concentrations in the atmosphere, which is six orders of magnitude lower than the concentrations that we're looking at in the paper. And so if you look at the ratio of just industrial emissions on Earth to these abiotic sources, it's overwhelming. And some of the gases, as far as we know, the limits are very strict. So less than 0.01 ppt per trillion for the C2F6, the C3F8, and NF3. We just don't see those coming from geologic sources.
All right, before we go to the detection, let me say hi to our viewers coming from Kenya, Wisconsin. And there is some languages that I can read here. I'm sorry, Brazil, Netherlands. Welcome. We are talking about the detection of greenhouse gases for technosignatures on the exoplanet. Eddie, and I have another question for you. OK, so we discussed about the idea behind the paper, basically, the detection of those complex molecules. And so now my question is, how are we going to detect those?
So that's basically describing your paper. You did some modeling. So if one of you can go through the description of the modeling to tell our viewers how you do this kind of analysis, that would be great. Sure. So in principle, these molecules are detectable in the same way that we would also detect all sorts of other biological or non-biological molecules in exoplanets. So there's really no different technique needed.
And as we actually showed in our paper, we don't even need to observe longer or better or in any sense different. So it's really these two methods that the viewers might already have heard about. So one is this transit method or transit transmission method where the planet moves in front of the star and some of the light of the star gets absorbed by this layer. by this upper layer of the atmosphere. So that is where the light of the star falls through the atmosphere of the planet.
And then we can see absorptions, for example, of these particular molecules. And then the other is what we broadly call direct imaging, where we use some sort of technique, either coronagraphs or nulling interferometry, where we really cancel out the light of the star to isolate the direct emission of the exoplanet itself. So that's really collecting the photons that come directly from the surface or at least the upper layers in the atmosphere of these exoplanets.
OK, so in the paper, you did some modeling assuming some type of specific exoplanet, right? I saw that you used TRAPPIST-1 as kind of a benchmark, basically? Yeah, for looking at the possible detectability of these gases with JWST, we assumed TRAPPIST-1f because it's sort of in the outer Hubble zone of the TRAPPIST-1 system. It receives significantly less radiation than the Earth receives from the sun.
And if it were to be warmed by traditional greenhouse gases like CO2 and water, it'd require like between 1 and 10 bars. That's 1 and 10 times Earth's entire atmospheric mass, but all in CO2. On the other hand, we looked at concentrations of these gases that have been previously proposed for terraforming Mars, and those range between 1 and 100 parts per million. of these specific gases like hexafluoroethane and sulfur hexafluoride.
And so we said, OK, if TRAPPIST-1f were otherwise Earth-like because it had been terraformed, and it had between 1 and 100 parts per million of these gases and or combinations of the gases, how many transits would be required in order to distinguish this spectrum from a planet without those gases? And because of the overwhelmingly strong absorption properties of these gases, it's surprisingly little.
It's as few as 5 to 10 for the higher concentrations, 100 part per million, and ranges down into the dozens of transits for some of the intermediate concentrations. And so we've also compared those absorption features to those that we'd see from, say, ozone, and they're just enormously larger than ozone.
So we probably don't have a hope of finding ozone on the TRAPPIST-1 planets, but if these planets have between one and 100 parts per million of our terraforming gases, then we might be able to see them. Okay, so just to clarify, so TRAPPIST-1 is an existing planetary system with seven non-exoplanets. Yes. It's a very small planetary system. It's smaller than Earth with an M-type star in the middle, which is relatively small, and seven exoplanets, which are relatively close to it.
But because the star is small and faint compared to the Sun, most of those exoplanets planets are outside, basically, that we call the habitable zone. So one F is one of the outer one, right? Well, yeah, it's in the traditional habitable zone, but it receives less, but it's in the outer part. So it would require more greenhouse gases than Earth has in order to be habitable.
But you're right, in comparison, to Earth and the Sun, it's much closer to the star because the star is so much less luminous. And so that entire planetary system would fit well inside the orbit of Mercury around the Sun. The difference, of course, is that star is less than 1% the luminosity of the Sun. And so the planets to receive the same amount of light or a similar amount of light are much, much closer. OK, so to show that the idea is not crazy and feasible, you use 1F as a reference.
And you say, OK, let's assume that those potential aliens living over there in this planetary system wants to make 1F habitable. They will put a certain amount of those gases in the atmosphere. Could you detect it with JWST, the James Webb Space Telescope, which is a telescope which is already running and taking data? Exactly. So, yeah, sorry. Go ahead. And so, yeah, go ahead. Yeah, so this is the point that I think is one of the big messages here.
So we already have telescopes that are strong enough to, in certain cases at least, find technosignatures in the atmosphere. So this is the first cool message, right? That James Webb is such a powerful tool that for, you know, a few special systems like TRAPPIST-1, we could already legitimately search for them, right?
And then we did the next step in the paper and looked even what's going on with the next generation of telescopes, in particular, this life telescope, the large interferometer for exoplanets that I'm working on here in Switzerland. We even looked farther and simulated a couple of scenarios.
So we put the same planet not just around TRAPPIST, but around a K star, a G star, you know, really like an Earth twin almost around a G star system and could show that With the next generation of telescopes, we not only can search for these signatures in a couple of selected systems as with James Webb, but really essentially our whole neighborhood up to, let's say, 30, 40 parsec. So that's the cool news. And if you find them, nobody knows.
But just to know that we have telescopes that are strong enough to do it, this is a really great thing to know and a great thing to look forward to and motivates us to build these things as soon as possible. Yeah, I just want to remind our viewers that astronomers don't have an infinite budget, unfortunately. So when you want to build an instrument, you need to basically show the feasibility, the capability of the instrument beforehand.
So what in this paper you're describing is that life, this telescope that you described, Daniel, will be able to detect the signature of this technosignature on exoplanets directly image. And that's remarkable. And we're not talking about some, it's not going to take years of data to do that. What I read in the paper is that in some cases, you can detect those signatures in five days. Exactly. So these signatures are so strong, especially in the mid infrared.
So we were talking about absorbing mid infrared radiation to keep the planet warm. Then, of course, it changes the mid infrared signature of the planet, especially strong. So this is why it's even easier to detect in a sense. So these signatures would show up. After five days, whereas classical biosignatures would need us 10 days, 20 days, even longer time to observe. So we would get them for free.
So technically we would get a search for technical signatures for free when we look for biosignatures. So as I mentioned before, we don't have to need a special instrument or anything. And then the other cool thing, the other way around is that these systems are also great, let's say, curveballs to throw at our instrument, right? So because they are really different from Mars, Venus, Earth, and they have a really weird mid-infrared spectrum.
So this is also what we need right now to test our instruments, to throw these crazy planets that we maybe just made up for now at our instruments to see if we can still detect those. So it's going both ways, really. OK, so we're going to take some questions from our viewers. There is some already popping up here. But I want maybe, Edith, you tell us a bit about the complexity of this modeling. Give us some information about how this was done.
Don't hesitate to go through the details, because people ask sometimes, how exactly you do this? Yeah, so you need to know how the molecules intrinsically react with light. And that requires measurements and it also requires or computational simulations that are very expensive. And they go through radiative transfer models, which incorporate the scattering and absorption of gases. among different atmospheric layers.
You've got to consider the type of light from the star and how the instrument responds at every given wavelength to that light to tell you how much noise there is and whether a signal can come through. And we're actually somewhat limited by some of those inputs I mentioned, you know, like, so how does the gas react with light?
So it turns out there's not a big, you know, industry in measuring these very potent greenhouse gases because, you know, I mean, actually, it's it's hard to get them for good reason. But and so, you know, for example, if we want to ask the question, could we see these things with something like the Haber World Reservoir, which is supposed to be the successor to Haber?
We actually can't answer that question because we don't know how those molecules interact with light at the wavelengths that HWI would observe. We don't have that data. Someone would have to measure it in the lab. So there's a lot of complexity that goes in, and it does result in some uncertainty.
But I think the general takeaway is these molecules are so absorptive in the mid-infrared that if they're present at any significant concentration, they're going to create a much bigger signature than some of the more traditional molecules that we've talked about, ozone and methane, CO2, et cetera. So do you think your paper will be sufficient to convince the TAC of JWST to give you a multiple orbit to observe 1F with NEOSPECT and detect the presence of those molecules?
I don't think that this science case specifically will be the justification for any kind of observing, specific observing program, which can be very expensive. The sort of takeaway of our paper is that you get it for free, right? So we're not claiming, you know, TRAPPIST-1 is likely to have these terraformed planets. But if they do, and you want to study those planets for other reasons, you know, do they have atmospheres? What's the composition of their atmosphere?
If these things are there, then they'll pop up and they'll probably pop up before other things. All right. So you're basically telling people, hey, if you're looking for water or carbon dioxide around by transmission in the TRAPPIST-1 system, look if you see also some absorption coming from those complex molecules that could indicate the presence of a technosignature civilization. Excellent. So we have a few questions. I'm going to start with the very simple one here from Meghdoot Mana.
Are we talking about exoplanets in our galaxy or what is the distance of those exoplanets that you discuss for Light Trappist-1? Yes, so those are really in our very, very closest galactic neighborhoods. So the TRAPPIST system is, I think, 30 parsec away roughly, so 100 light years. So most of the planets that we will observe in the future that are close enough that we get enough signal of them are all, let's say, within a radius of 100, maybe 200 light years.
So in comparison to our whole galaxy, this is really... not even a percent of the whole distance. So it's really just our tiny, tiny neighborhood around us here that we can search for these.
yeah yes 41 light years for this one i remember this because i've been like when we discover when they discover this system everybody knew there would be kind of a reference for most paper because it's so close and so bright that uh it would be a main target for jwst at the time okay some people about talk about this terra formation and if we can learn something about By studying Terraform, planet being Terraform, we can learn something about our own planet.
So our art with art, our hearts with art. My glasses are bad today. From Netherlands. She's asking if learning about terraforming planets, I'm interpreting this question, I'm sorry, but learning about terraforming planets could help us understand how our planet works or how we can basically change the climate on our own planet. Well, these gases do exist in Earth's atmosphere in small amounts, parts per trillion, tens of parts per trillion.
And they're very bad because they're exacerbating the warming that's coming from CO2. So for us, we don't want these gases in the atmosphere. And some of the advantages that we talked about for them, that they live a long time, that they're so much powerful than CO2, it's not great for us. You know, it's a reminder that it's not just the carbon dioxide we're putting into the atmosphere that's affecting the climate, it's other industrial products.
But I do think that, you know, the idea of terraforming Mars, the idea of rendering other areas in the solar system habitable artificially, I mean, it gives a lot of people, it interests a lot of people, you know, in terms of space exploration, what's the future of humanity? And I think, you know, that's the level of optimism we should embrace, what's in the future for the human race.
Okay. Leslie Anderson has a question that is being asked every time we talk about the search for extraterrestrial civilizations. So I want to hear your point of view on this. Will other life necessarily need to have the same elements that our planets require, or has it been considered that it could be vastly different? So think of an answer to this question in the framework of your research. I have an answer, but I want to hear your view on that.
I mean, honestly, this is kind of like the question we want to answer, right? So we are scientists and we want to ideally want to find life in our neighborhood, but we should also be ready for the fact that we don't find anything. And then if you find anything, you should not just look for the life as we know it. So so I'm trying to approach this.
this problem very scientifically super unbiased and really, you know, built my instrument good enough to find what we know, but also broad enough to see things that we haven't, you know, anticipated. So I'm trying to be neutral as someone who is in Switzerland. Okay. Benji, you want to add something about that? Yeah, I mean, I would say that, you know, this type of search for terraformed planets doesn't necessarily require them to be made of the same things.
It just requires them to want to be at roughly the temperature where liquid water exists. And so other things could be different, but they'd want, you know, the planet to be roughly in the same temperature range as Earth and want to modify the climate to make that happen. Yes, because the presence of water always on our planet, we have seen that as soon we had liquid water, energy and complex molecule life appear, even when our planet was not hospitable.
I mean, we're talking about 4.2 billion years ago. We had some kind of bacteria that thrive in ponds, apparently, and we have still detected this kind of life. So here, the research is not about searching directly for... those aliens by searching for how those aliens modify the planet so there is temperate climate liquid water on the surface which could be an indication of life okay um let's see there is another question um I mean, if I can briefly follow up on this.
So I think it's the same for biosignatures, but maybe not purposefully, right? So if we look for life on exoplanets, we always search for life that is able to change the climate or change the atmosphere on a global scale. at least for exoplanets, we will never remotely detect, you know, a Mars-like planet where there are few microbes under a stone or something like that.
So what we always need to remotely detect it is something, be it alien civilizations or just the ocean full of algae that changes the whole atmosphere, right? So in that sense, it's the same problem for both. Okay. Well, that brings me to my last question. So Eddy, can you tell me the story of this paper? Like how this idea came out? What's the motivation behind this research? Well, it has a long history.
In part, I read about terraforming Mars as a graduate student, and I thought, hey, could we find this on another planet? And of course, in the tradition of PhD students, this idea sat around for a long time. Of course, other people have been thinking along similar lines. How do we find planetary technosignatures? We had a meeting called Technoclimbs in 2020, which is a NASA-sponsored meeting, virtual, in order to discuss different types of planetary technosignatures.
We mentioned some of these gases, but no one had done the simulations. And so we built a team that included me and Daniel and many others to really do these simulations and demonstrate quantitatively, can we detect these, and we could, with current and future instrumentation. Okay. That's the way Science Journeys work. You meet people in a conference, virtually or in person. There's some ideas and you put a team together and you hand us a paper that's being mentioned everywhere in the world.
Daniel, can you tell us a bit about the Statue of Life and maybe where we're going with this project? Because I know people have been hearing about this for several months now. Yeah, so LIFE is at the moment an initiative, I would call it, that we started in Europe three, four, five years ago. And it's built on ideas of space telescope concepts that were already there about 10, 15 years ago, some even 20 years ago.
So for the older folks in the audience, maybe remember the TPFI, the Terrestrial Planet Finder Interferometer. In Europe, there was a mission proposed called Darwin. So the rough idea is for at least four telescopes put together and the light collected in the fifth telescope. And this is if you ask many people in the in the in the community the best way to get the spectra in the mid-infrared for the spectra. So, I mean, that's the reason why people thought about this 20 years ago.
And right now we are really pushing the idea from Europe all over the world. At the moment there are signs by ESA that they might consider it for one of the future missions in the 2040s. But we are a bit impatient, obviously, so we rather want to want to do it faster. And so we are right now actually working on showing ESA that we can do it faster than their timescales. So this is where we are at now. So, OK, that's what I mentioned before. I really want to do these observations.
We have the technology here. So let's build the telescope. So this is really the spirit that we have right now in the life team. And if anyone is out there that wants to support us, you know, contact us, of course. I was just about to say that. So are we talking about a budget of what? 100 million, 10 million, 1 billion? What is the cost or something like that? So that's actually what we are right now working on.
So we are preparing for a study to work with the industry to get a serious price tag on this. So it's going to be in the same order of other space telescopes. So it's not going to be 100 billion, but it's probably also going to be more expensive than 1 billion. So we are talking three orders of magnitude here. But we don't need the money tomorrow. Right now, a couple of million maybe would help us to push that plan for the next two years, as it is with strategic investments.
So if you want to strategically invest in this idea, you don't need to give us a billion. We would be happy with 10 million maybe. So this is right now how it goes. And then eventually it's like a snowball. Once you pull this and pull the community, then these things are just going to work. 2030, 2040, maybe. Okay. Well, I want to thank Julia for the star on Facebook before I forget. And Eddie, my last question for you. What's the next project you're working on?
Well, for this specific project, looking at technosignatures, in part, we want to understand how we could find technosignatures with the Howard World Observatory, which is funded. It's under development by NASA with probably a launch date in the 2040s. But again, we lack some of the fundamental inputs and data for understanding how much of a certain gas would you need in an atmosphere in order to be detectable.
And that applies not just to certain technosignature gases like the ones we looked in this paper, but also potential biosignature gases and other things that we may look for to assess geological processes in exoplanets. So it's kind of filling in those gaps before the telescope launches. So I'm really interested in those types of things. Okay. Well, I have the feeling I'm going to hear about you two very soon in the future for some reasons.
So thank you very much to both of you for coming to talk to our audience about this remarkable work you've been doing and published recently. Thank you to all our viewers for being watching us from everywhere on this planet. Don't forget, this is the CETI Life. We are a program of the CETI Institute, a nonprofit organization. You can follow us, go to our website, CETI.org. You can join our newsletter called Journey. follow our YouTube page, and Twitter, and Nix, and et cetera.
We're on every platform, I think. Just if you like this video and you want to help us, you can just click Like right now, or enroll, join us, register to receive these videos when we publish them. And if you want to help Daniel to build his life telescope, you can go to citydog.org slash give now and give this $10 million that he mentioned he will need to start this telescope.
You can give us less than that, and we will continue to talk about those remarkable projects in the field of astrobiology. So thank you very much, everybody. Thanks again, Daniel, Eddie, and see you soon. Bye-bye.