NASA's Curious Universe - The Search For Life: Are We Alone?

Episode Date: June 21, 2022

Are we alone in the universe? It's a question studied in science fiction, but also by teams here at NASA. Join us as we search for signs of life outside of Earth with scientists Aki Roberge, Ravi Kopparapu, and Shawn Domagal-Goldman.

When I was in undergrad, people thought planets were really rare beasts, that it took really particular recipes to make a solar system like ours. Since then, we've found that planets are common. They're not hard to make, and in fact, they're amazingly easy to make. That means there's a ton of real estate out there that could potentially be Earth-like. And on top of which, the chemicals of life, are the most common chemicals in the universe. So if you've got the planet is like, I don't know,

your frying pan and you've got the recipe, the ingredients for life too, seems to me like it's pretty likely that nature will have put the ingredients in the pan and hopefully actually made, you know, more life out there. This is NASA's curious universe. Our universe is a wild and wonderful place. I'm your host, Patty Boyd,

and in this podcast, NASA is your tour guide. Are we alone in the universe? We are fascinated by what it would mean to find life on another planet. Our Earth is teeming with life. From lush forests with thousands of interconnected species to vast ecosystems in the ocean, from complex microorganisms to cities full of people,

our planet is alive with activity. But what else could be out there? We haven't found signs of life anywhere else in our solar system, but that certainly doesn't mean we aren't looking. And even further beyond, there are hundreds of billions of galaxies in the observable universe, full of stars, planets, and moons that we have only begun to discover.

Scientists right here at NASA are combing the universe for signs of life at all states. and trying to answer the question, are we alone? My name is Sean Damagel Goldman. I am a research-based scientist at NASA's Goddard Space Flight Center, and I'm an astrobiologist, which means I think about the ways we can look for signs of life on planets beyond Earth. My day-to-day work is actually a lot like other people's day-to-day work.

I spent a lot of time answering emails, I spent a lot of time in meetings. The difference is the subject. For me, the subject of those emails and meetings is all about the search for life. And that makes a lot of those, what sounds like more boring things, a lot more fun. Astrobiology is a fascinating field where scientists like Sean are looking for life among the stars. It might sound like a term straight out of science fiction, but it's a very real department here at NASA, focused on a lot of different areas. Not only are we using tools to search the stars for science of life,

we're trying to better understand life here on Earth so we can try to find it elsewhere in the universe. It's an interdisciplinary field, combining the study of how life emerged and evolved here on Earth with designing tools like telescopes, satellites, rockets, and rovers we can use to look beyond Earth. It's also doing the work of kind of philosophical questions, like what is life in the first place if we're looking for life? We try to stitch all of that together, take everything we've learned about life's history on Earth,

and everything we know about what we can build today so we can do that search on other planets tomorrow. Integrating all of it together, to me is really what astrobiology is. So how exactly is NASA looking for these signs of life? Well, there are lots of ways from doing fascinating fieldwork right here on Earth to sending rovers and planetary sample missions into our solar system. But to search for signs of life that might be really, really far away, light years away, you're going to need a telescope. Hi, I'm Occupor Birch, and I am an astrophysicist at NASA.

I work on helping people, engineers, and our technologists develop ideas for future space telescopes, like future super-hubbles, that would be able to study exoplanets around other stars. In particular, find out if any of them are actually like the Earth, with oceans and atmospheres and maybe even life on them. Aki is helping to plan future telescopes that will scan the universe for signs of life. And while technologists and engineers will be the ones building out the telescope itself, astrophysicists like Aki helps start the planning process with questions. To look for life on planets around other stars, we need to use the tools of astronomy. That means telescopes. And so you start thinking, well, what kind of data do I need to really answer?

this question. This is where the scientists come in. This is why the missions they start with the science. NASA missions are currently targeting three primary regions in the search for life, Mars, icy moons that orbit planets in our solar system, and far-way worlds beyond our solar system, called exoplanets. While that search may seem complicated, astrobiologists start with what we know and go from there. It all comes down to what you. what you think life needs. And all the life on this planet, anyway, needs liquid water at some point in its life cycle. Mars, it looks like, maybe had liquid water on its surface.

Actually, it's pretty certain that it did at some point. It doesn't today, but it did once. So it's a really good place to look and see if life arose there in the past. We use a lot of different tools to look for life on Mars. has sent five robotic vehicles to Mars called rovers, which explore the red planet and will one day bring back samples for us to study in the lab. But then again, okay, liquid water. Where else the solar system has got liquid water? Ah, those icy moons of the outer solar system that have ice-covered shells over these deep oceans that are heated from the bottom. Now looks even more

promising because that happens on Earth. There's life at geothermal vents at the bottoms of our oceans. so that's a good place to look too. These icy ocean moons include Enceladus, which orbits around Saturn, and Europa, one of Jupiter's 80 moons. Even within our solar system, it's harder for us to send a rover to these worlds than it is to visit our neighbor, Mars.

Then, if you want to find environments that are really like the Earth, you have to go outside the solar system. The Earth is unique in the solar system, in that it's got liquid surface water and a global biosphere that is so abundant, it's changing the chemistry of the whole atmosphere. We know there aren't any other environments

in the solar system like that. So if we want to find the ones that are really like the Earth, you have to go to other stars. From the information that we have already, it looks like there are more planets than stars in the galaxy. We've discovered a lot of the exoplanets, but right now we don't know a lot about them. We basically know how big they are, and we know how far away from their star they are.

But that's not a lot more. So we're really pushing now, first with the James Webb Space Telescope, and then with these future telescopes that I work on, to actually try and do a better job of finding out what the planets are actually like. You might remember this from one of our season three episodes. Exoplanets are planets outside our solar system that orbit stars other than our sun. As of 2022, we've discovered just over 5,000 unique exoplanets with the help of different telescopes, including Hubble, Kepler, and Tess, the transiting exoplanet survey satellite.

We also have tons of new information coming to us soon, thanks to our newest tool, the James Webb Space Telescope. Since these exoplanets are so far away, astrobiologists like Sean search for clues about their composition, atmosphere, and habitability with data rather than with detailed pictures. Now we're not going to get a map of those worlds, not even like an old 8-bit pixelated blocky map like from the video games I played when I grew up. We're going to get literally one dot of light,

which isn't really a lot to go on if you want to look for a forest or something like that. The information we get back from these powerful telescopes is so limited. It's often just one pixel of light. light in an image of the night sky. By looking at that pixel of light as a spectrum of different colors or wavelengths, we can learn more about what the planet is made of and how it operates.

When you start pulling that data apart, we can discover fascinating things. Once we do that, we'll be able to look for sort of the fingerprints that certain gases have. And if we find the gases that life makes, like oxygen, or methane, then we think we found something. At that point, we're back into the scientific method because someone somewhere is going to say, well, I know some other way to make oxygen or I know some other way to make methane or whatever our fingerprint is that we found of life. Someone somewhere will say, I know a way to do that without biology.

But either way, we'll have at that point hypotheses to test and build another generation of telescopes or maybe one day we do send something to fly by those worlds. I'm Ravi Koparapu. I'm a planetary scientist at NASA Garden. I look for alien life on other planets. Whenever someone asks my daughter, she says that my dad finds aliens, and that's as simple as that.

Ravi is also a NASA scientist, intent on finding whatever life could exist in the universe. And he does that a couple of different ways, looking for direct and indirect hints of life. So many of the searches right now that NASA and other scientists, other institutions are trying to find are some signs of biosignatures.

What does that mean? It's the signatures of biology happening on a planet. And so those kind of signatures are the ones that many of NASA missions and NASA telescopes are going to look for. The best way to find life is to get to know life. Our Earth has housed all kinds of biology for a pretty long time. The world of dinosaurs was so different than the world we live in today. And even now there's wacky ways of life all over the place.

A big part of astrobiology is field research right here on Earth. Astrobiologists look to understand how life works all over the world. From lava tubes of Hawaii and acid mines in Spain to deep sea vents in the Caribbean and the frozen lakes of the Antarctic. Thinking back on what our home planet has looked like over the eons, as well as the variety of ways Earth looks now, helps us figure out what we should be searching for on other planets. Earth had several biosignatures over its lifetime. Earth is about 4.5 billion years old. And life on Earth thrive for about 3, 3.5 billion years. Over time, our biosignatures changed.

Right now, we think, oh, yeah, you know, if we have oxygen and some sort of a nitrogen atmosphere, it should be fine. That's their life, right? But that's the current Earth right now. About 2 billion years ago, there was no oxygen. A lot of methane-loving organisms. Most of Earth's history doesn't include life as we know it today. For a long time, life on Earth meant microorganisms, you know, like bacteria, fungi. Intelligent life is a blip on Earth's timeline, but organisms have lasted much longer, which is why the majority of NASA's extraterrestrial search is for indicators of bacterial life. It's important, I guess, to remember that humans, we are not in the majority on this planet.

It's plants, it's bacteria. They outnumber us by a lot. So that's the kind of life that we think we can detect from interstellar distances, which is really far away. If you find a planet that has a lot of methane and CO2 and water and oxygen and nitrogen and things like that, There is a good sign that that planet may be active in biology. That doesn't necessarily mean that it is for sure a habitable planet. But it's a good sign. Beyond that, we also want to find techno-signatures. Just like a biosignature, it's a sign of biology.

Technosignature is also a sign of technology on a planet. Some of them that we have worked on are pollutions. If a planet has a very industrialized civilization, just like us, they might be emitting pollutants as a byproduct of their industrialized activity. This is where our hypotheses get really creative. Technosignatures, another very real sci-fi concept in our scientists' arsenal, are indicators of advanced civilization on a planet. Just like we humans have made our mark on the Earth, so could have been a world. another species change their planet? And if we can see similar changes on another planet, we can start to wonder if something alive was responsible for them. Based on how Earth functions,

we already know of things in our atmosphere that weren't made naturally. Chloroflorocarbons, for example, we use that in our refrigerants. Nitrogen dioxide, for example, it comes from the vehicle emissions that we are using fossil fuels, right? We use fossil fuels for almost everything. So if using a fossil fuel, you might be generating nitrogen dioxide. We can use that as a signature. We can use city lights, nightside city lights. If you see a planet in the night side, you see lots of bright things. That's a city light. Radio communication. We can look for probes within our solar system that other civilizations have sent to us. Imagine this. NASA is sending Voyager probes, pioneer probes, to outer parts of our solar system. They've already crossed our solar system.

and gone outside. If we can do it, they might also be doing it. The SETI Institute, which stands for Search for Extraterrestrial Intelligence, is looking for this kind of advanced life, keeping an eye and an ear out for any sort of communication that might be coming our way from an extraterrestrial neighbor. But what if life elsewhere doesn't look anything like life here? How could we begin to guess about the processes of life we don't even know exist?

That's why scientists spend a lot of time thinking about it, and they start from what we do know. This is one of the most challenging parts of astrobiology, because we're talking about aliens, right? Like, alien life should be alien to us, and it should be weird, and it should be different. However, if you go too far, you can look for things that just really aren't plausible. That is a really hard tension to work out. The way that we practically carry that out, right, is we look for life in the most likely places, in the ways we know how to detect it first. And the thing I remind people when I talk about this is this is just the first generation

of these things we're going to do. We're going to look for Earth-like life on Mars and these icy worlds and on exoplanets. And if we don't find it, it might be because those places are all dead. It also might be because the life on those places is truly weird and we have to think more creatively and more alien-like to find them with a second generation of missions. If you told me you lost your keys, I would have a bunch of ideas where you might look. And it would be based on my own experiences. I would say, look in the coat you wore yesterday, look in the pants you wore yesterday if

your pants have pockets. Look in your couch cushions. Look in your car, maybe under the car seat, or in the cup holder. Maybe look in your door because I've been forgetful enough to leave my key in my front door on my way in. That's not all the theoretical places your keys could be, but I find a lot of keys. You can extrapolate from Earth-based life to start your search. And just don't call at the end. Don't say that the universe is devoid of life if you don't find it. just start with what's familiar. And then if that doesn't work, maybe focus and hone your search to the specific environment you have not yet found life in.

And then the third step is to try to get really creative. But for me, it's like you start with the familiar and then branch out. When NASA is looking for life on our planets, trying to explore the galaxy or looking for planets, science is the spearhead for everything. Science decides if you have the right data, science decides if you have the right data,

the right conclusion. If science says that you do not have that, it is not there. And that's what we keep our heads down and look for when we are looking for life on other planets. Science should be the first and the last thing we have to do before we announce anything to anyone else. Finding evidence of life on Mars, an icy moon, or a far-off exoplanet would be groundbreaking. It's a discovery that would fundamentally change our understanding of the universe. But it also would take a lot of verification, testing, study, and debate

before we knew for certain what we'd found. Imagine you're the scientist who sees the first sign of life. How would it feel to make such a monumental discovery? If you're Sean, the first thing you do is call your mom. If it's just me sitting with the data, I'm definitely calling my family members.

my mom, my brother, my wife and my daughter, tell them all about it. The next step would be to talk to the colleagues on the team I'm on, because this is almost certainly not me looking at the data. It's probably like a bunch of us in a control room somewhere all staring at our screens with our jaws open at what we're seeing. The next step is we're probably going to put it through a series of tests to make sure what we think is biology is actually biology and not some astronomical or geological or chemical process. And then after all that, we'd probably write up a paper. And at that point, people that weren't on the team are going to take a really critical eye to it, probably many people. And they're going to try

to find flaws in our arguments. And if it gets through them and is accepted and people let us publish a paper that says, we're not alone, that'll then go out to the public. And it'll probably happen simultaneous with a press conference. And that moment to me is really special, because it might be the moment that the world finds out that we're not alone. However, we as scientists, won't know it's that moment for years. And the reason we won't know is even if I was sitting on that stage in that press conference saying we found evidence that we're not alone, I would know as a scientist that statement is only going to be accepted after about 10 to 20 years of argument and debate with the rest of the scientific community. And it's quite possible we were

wrong, but we won't know whether we're right or wrong until the scientific method can play out for really another generation of scientists. Before we know whether or not that original sign of life that we claim to have discovered was really evidence that we're not alone or just some false positive that we thought was biology, but was really some other process we didn't understand. It's probably not going to be, we took this one piece of data and, ta-da, there it is. It's probably going to be like, oh, that's weird. And then we'll take another piece of data, and it'll be like, ooh, okay, that's weird too.

But it makes sense with this other piece of weird. That's kind of like how all scientific discovery goes. It's really rare that it's just like, Eureka, I took this one thing and I know exactly what it means. Vast majority of time, that's not how it works. The real amazing phrase that scientists says to themselves when they're on the cusp of discovery, it's not Eureka. It's actually, that's weird.

We are at the very beginning of understanding who we are and what our place is in the universe. Sean, Ravi, Aki, and others are laying the groundwork for future missions that will search for signs of life far beyond our solar system. It is such an exciting time for astrobiology, a time of brainstorming, planning, self-reflection, and study that could one day yield incredible results. The stuff that I want to be a part of, all these missions, are going to look for life, they are going to be happening for the next five to ten to twenty years. Even a five-year-old today could be done with college and writing their PhD dissertation on the data from one of these missions looking for life. There's plenty of time for people to get involved. For me, the dream is when I retire that I'll be able to take my grandkids

out and point at the night sky and be like, that star over there, there's a planet around that star that is inhabited globally like our planet, like our home. We don't know what kind of life is there yet, but that's your generation's mission to figure that part of. This is NASA's Curious Universe. This episode was written and produced by Christina Dana. Our executive producer is Katie Atkinson. The Curious Universe team includes Maddie Arnold and Michaela Sosby with support from Caroline

Capone and Juliet Goodconnect. Our theme song was composed by Matt Russo and Andrew Santiguida of System Sounds. Special thanks to Claire Andrioli, Amber Strawn, Barb Madsen, Tahira Allen, Mike Twyong, and the astrophysics team. If you liked this episode, please let us know by leaving us a review, tweeting about the show at NASA, and sharing NASA's Curious Universe with a friend. And remember, you can follow NASA's Curious Universe in your favorite podcast. app to get a notification each time we post a new episode.

So let's say you're invited to a party by someone you don't know much. The first thing you do is to go to someone you already know so that you can strike up a conversation and then start introducing yours, well, maybe, and so on. That's exactly what we are doing with Search for Life. We don't know what life looks like. We don't know anyone there. And the first thing we want to look for is Earth-like life. Amazing.

Terrifying and amazing. This is no terrifying. at all. I mean, if we are finding our neighbors, right? So, neighbors are fine, I think.