Why don’t we go live on Saturn’s moon Titan? What would it mean if we found life elsewhere? How did life get its start on Earth? NASA’s chief scientist Jim Green and astrobiologist Lindsay Hays discuss these and other audience questions from social media.

Jim Green:Is there life on Mars or Titan or Venus? Where would we go to look for life? We’re here to answer your burning questions about life in the universe.

Jim Green: Hi, I’m Jim Green, chief scientist at NASA, and this is Gravity Assist. On this season of Gravity Assist we’re looking for life beyond Earth.

Jim Green:I’ve invited Dr. Lindsay Hayes back to sit down with me and answer your questions.

Jim Green:And she’s an expert in astrobiology. In fact, she’s the deputy program scientist for the Astrobiology Program at NASA.

Jim Green:Welcome, Lindsay to Gravity Assist.

Lindsay Hays:Thanks, Jim. I’m really glad to be here.

Jim Green:Now, helping us today is Liz Landau, and she’s been the fabulous producer of gravity assist now for quite some time and doing as, you all know, a super job. So I want to thank Liz, bottom of my heart, and, and turn it over to her because she’s gonna really give us the questions you want to know about is there life beyond Earth. Liz!

Elizabeth Landau:Well, thank you, Jim. It’s been such a pleasure working on Gravity Assist, and we’ve learned so much about life’s origins and the search for life beyond Earth. So let’s go into social media and see what our audience is asking.

Elizabeth Landau:So the first question comes from @nsulakshna, who asks, “age old question: Is life possible outside Earth? Has anyone found any living organisms?”

Jim Green: Okay, I would say from a professional opinion, we find environments all over the place that we feel, could be habitable environments. And that means regions where we think life existed or could have existed in the past. So, we haven’t found life yet. But those regions are of particular importance.

Lindsay Hays:Yeah, I mean I’d add, like, I think that, you know, we know on this planet on the Earth, there’s sort of diverse environments in terms of where we find life, you know, we find life in very hot environments, very cold, very salty, very radioactive, all of these things. So, the range of what we know, based on what we’ve seen on this planet as habitable, sort of, is quite wide, and we see diverse environments throughout other bodies in the solar system.

Lindsay Hays:So, it’s likely that somewhere there is, somewhere as habitable for life as we know it. And even more likely that there’s probably somewhere that is habitable for life as we don’t know it, you know, something that we, something that’s different enough from Earth life that may have a different range of temperature or whatever that, that, that may exist somewhere in our solar system or beyond.

Lindsay Hays:I would say, Jim, I don’t think we’ve really been to a place and said, yeah, this place is definitely habitable for Earth life. But we haven’t technically been to that many places in our solar system yet. “Yet” being the operative word there. And so, you know, I think I think as we continue to explore, we may find more habitable places that we know are likely out there.

Elizabeth Landau:Excellent. Well, let’s go to our next question, from @HomelanderAdc, who asks, “What’s the most plausible theory of how life appeared on Earth?”

Lindsay Hays:You know, I think that the way that we as astrobiologists think about how life appeared on Earth, it was sort of a very gradual process. Organic chemistry, sort of the abiotic chemistry, things that happened just because you have the right chemicals and the right energy in place, you know, slowly turns into, you know, in places that have enough energy to push these reactions forward, but not sort of spin them out of control. These things slowly happened, the chemistry continued over a lot of time, that’s the good thing about the solar system is, we have a lot of time for these things to happen. You know, a lot of complex chemistry was probably what was happening early on. We probably wouldn’t look at it and recognize it as life.

Lindsay Hays:And then there was selection processes that happened on this, it was very messy, I would think that, you know, our most plausible theory is that the origin of life was something that may not look a lot like life, would have been a very messy and a very complex chemical soup, and very inefficient, right? You may have done some of the processes that we think of but not as not as well as life does them now. Metabolism, replication, all of these things, eating, you know, eating, and, you know, breathing and reproducing, all of these things may have happened, but in a very inefficient kind of way.

Elizabeth Landau:And a question that came from Twitter and was getting a lot of attention was from @PaigeEtheridge1. She asked, “Are you open to the idea that not all life forms might be carbon based?”

Jim Green: Oh, absolutely. In fact, you know, what happened about 15 years ago, was, was really quite fascinating to watch when the astrobiologists were struggling, I think, for the really first time to create a definition for life, okay. So, so that definition has got to be such that it doesn’t just mean it has to be carbon life, you know, you, so you, it’s got to be all-encompassing. And I remember the time Mary Voytek and I talked about this, and Mary is the head of the astrobiology program at NASA.

Jim Green: So Mary told me, life has three attributes. Okay. It metabolizes, that means that it brings in a liquid, which, with, with material that then is a solvent that takes the nutrients out, and then the liquid is used to eliminate the waste from that material. That’s the metabolism aspect of it, and then it, and then it reproduces, and then it evolves. And that’s it. So that doesn’t say anything about its composition, you know, whether it’s silicon-based or carbon-based. And so, that’s, that’s the top definition I think of when we talk about life.

Lindsay Hays:You know, that’s, that’s all very true. Although I will also note, you know, I’ve had a lot of conversations with people, I mean, life without carbon base, non-carbon-based life non, you know, other elements that we’re used to based life, is certainly possible. Although, you know, I’ve also had some conversations with our, with our astrobiologists, who point out that, you know, a lot of the abiotic chemistry in our solar system looks like the chemistry of the life that we know, right?

Lindsay Hays:And that has to do with the fact that, you know, given the way that elements form in our universe, the smaller elements, the ones that we think of the CHNOPS, ch, n, o, p, s, carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur, those are some of the most abundant elements in this universe. And therefore, you know, on one hand, it’s certainly possible that life could form on other planets where the energetics are different.

Lindsay Hays:But it’s also worth noting that when these elements are the most common elements, there’s also a likelihood that life will pick up and use at least some of them in their, in their general chemistry, and that the sort of state of chemistry in the solar system, at least in our solar system, is such that a lot of the chemistry that we see does tend to be carbon-based, and those sorts of things. So not ruling it out. But certainly the likelihood indicates that carbon-based life form is possible. I mean, we’re here.

Elizabeth Landau:Awesome. Well, let’s talk about some places in the solar system that are interesting in terms of astrobiology. @WarlockAdventur asks: “Why if Titan has an atmosphere similar to Earth’s, are we not entertaining the idea of a base on Titan, as well as the Moon?”

Lindsay Hays:Oh, boy, would that be cold! You know, the comment, the idea that Titan’s atmosphere is similar to Earth’s. Well, it’s certainly similar in pressure. It’s about what, one and a half times Earth’s? And its predominance of nitrogen, right, just like the Earth, it’s high nitrogen. But it’s very, very different in terms of temperature, it’s, you know, minus 290 or so Fahrenheit, which is quite. quite cold. And, and it’s non-nitrogen content, you know, we think of our Earth as an oxidizing atmosphere. If you leave iron on the surface, it will rust and other types of things like that happen because of the high content of oxygen we have.

Lindsay Hays:Whereas on Titan, you know, lots and lots of hydrocarbons of various forms and types. Our human exploration, people could speak to this, probably more than I could, but keeping a base warm on Titan would be really, really difficult. Because you’ve got this thick, very cold atmosphere, and that you’d be you know, be kind of, kind of difficult to do that. Also, being as far out as it is in the solar system and the opaque atmosphere would make solar energy a really hard thing to come by, you know, and would require figuring out a lot about how to use sort of local chemistry for energy.

Jim Green:Yeah. In fact, Titan, although has similarities of Earth, as we pointed out, there are also some dissimilarities. Here on Earth, we have also enough greenhouse gases, like carbon dioxide. Water vapor is a greenhouse gas, so is methane, that actually our atmosphere is warmed well above, you know, maybe about 80 degrees Fahrenheit, if we didn’t have those constituents. Titan is different in the sense that it doesn’t have the greenhouse gases, in effect, because of the haze reflects sunlight. And so it’s colder than what it would normally be if it’s sat in orbit around Saturn.

Jim Green:But one thing about Titan that we absolutely have to mention relative to the life story, is that when we talk about the metabolism part as the first definition of life, that metabolism included, remember, having a liquid. And on Titan, there is a liquid, it’s liquid methane. There are lakes of liquid methane, in fact, in the southern hemisphere, right now, it’s raining methane.

Jim Green:And the drops are really big, you know, they’re several times the size of our own drops. So if you’re walking around on Titan, you know, this stuff is, is coming down slow, and it’s big drops, so, so very exciting, very exciting atmosphere. And so, the “weird life” scientists really want to go to Titan because if life exists on Titan, it’s gonna be completely different than what we’re familiar with here on Earth.

Elizabeth Landau:Definitely. And while we’re not going to build a base anytime soon, we are sending the Dragonfly mission later in this decade to investigate Titan. So, very exciting stuff.

Elizabeth Landau:Let’s move on to Mars. @masada_osamu asks: Anything so far on Mars, any creatures or bacteria or anything with life?

Jim Green:Well, nothing that we’ve found so far. But the, the more we, we explore Mars, and you have to remember, we’re only exploring the surface. What we see in that surface is a lot of the history of Mars is coming through in the rock record, even that laying on the surface. So we see, we see ancient river valleys, we see ancient deltas, we see areas on Mars that had water in the past and a lot of it for long periods of time. So then the concept would be: life could have existed in those environments millions of years ago, because Mars has had rapid climate change, and has been pretty arid on the surface for several billion years since then. What we don’t know as much about the environment below the surface.

Jim Green:We only get hints of that. For instance, Mars, on occasion will burp methane and we find that this methane is leaking through the surface. Okay. And that’s pretty exciting, ’cause methane is one of those gases that that we call a biomarker. You know, it could be generated by life, doesn’t mean it is, because there’s also abiotic, meaning non-biological methods, for which methane could be generated. And now we’re seeing Mars also burp oxygen, molecular oxygen, O-2. And so that’s another one of those gases that that that, you know, we are familiar with as an important element of life here on Earth. So, we just, one of these days got to understand much more about what’s going on below the surface on Mars.

Lindsay Hays:Yeah, you know, my background in organic chemistry, I’m always interested in looking for biomarkers and biosignatures and whether or not those are things like gases, methane, oxygen, those types of things or, you know, lipids.

Lindsay Hays:If you’re really, really lucky, the part of you that will last a billion years is your cholesterol. You know, what are the extraterrestrial life equivalents of those? You know, if there was Mars life, are there are there some type of lipid, some type of hydrocarbon that was preserved on the surface? You know, those are the kinds of things that we’re looking at and looking for. We haven’t found anything yet, as, as Jim said. But you know, there’s some there’s some really tantalizing hints about Mars’s past habitability, which I think is what keeps us going back and keeps us exploring and wanting to learn more about our red neighbor.

Elizabeth Landau:Absolutely. Well, let’s move on to Jupiter’s moon Europa, @Zero_grav1ty, except the “i” is a “1,” asks, “What about the moon Europa? How hopeful are you guys finding life on Europa?”

Jim Green: Okay, for my, from my perspective, Europa is a real gem in the sense that it’s got a wonderful liquid environment, we know that it has perhaps twice as, twice the amount of water underneath this icy crust in an ocean that surrounds a core, a rocky core on top of that, and, and when we look at the ice structures in this crust, we see hardly any craters, which means that the ocean must be communicating to the surface somehow. In fact, there’s some indications that that these cracks that we see are because of one plate of ice is moving under another, like subduction that we see here on Earth with one layer moving underneath another. This means Europa is a living world, a body where the geology is changing on, on a regular basis. And in therefore, it has a lot of Earth analogies, you know, Earth is that living planet too, where the geology is moving and changing and active. And so that environment for Europa, we talked about it, is is indeed, you know, if it has all the right chemicals, and it has that water, does it have the time to create life? And Europa has been this beautiful moon of Jupiter with all these features for the last four-and-a-half billion years! Okay, so it is had gobs of time, if it has all the right stuff, to have developed life.

Lindsay Hays:Yeah, time is certainly one of those things in astrobiology and you know, origin of life and chemistry that is hugely important. We often think about going and exploring as snapshots, we go and look at what it’s like right now, or we get a snapshot, a geological snapshot of a point in history. That’s one great thing about Mars, right? We can see so far into the past on Mars in ways that we can’t even on this planet. And you’re right, Europa is great for that time. The fact that it looks like it’s this active planet with this, you know, this, this cycling of the surface and all of that, is hugely important. I’m really excited to see with the, what the upcoming Europa mission tells us more about this, really, as you said the gem in the solar system, Jim.

Elizabeth Landau:Definitely. I’m also really excited about Europa Clipper. And another person, @ScottBSNRN, asks, “Will you ever look for life on Neptune’s moon Triton?”

Jim Green:Right. Well, Triton is a fabulous object. Because it we now believe it is a captured moon. And, and if you captured this, where did this body come from? Well, we believe it came from the outer reaches of the solar system. And those objects that were formed, we call Kuiper Belt Objects. So we believe Triton is a Kuiper Belt object. It’s more like Pluto than anything else. It doesn’t look like an asteroid, doesn’t look like a comet, it is really a mixture where a lot of these ices we see in the outer part of our solar system have, have been formulated into this beautiful round body Triton. Triton also is active.

Jim Green:You know, when the Voyagers flew by Neptune, they see these geysers and it, these are things black soot, I believe they think it is, that’s upwelling in pockets on the moon. And in so any body like that, it could be active. So there’s some sort of energy activity going on. And if it’s anything like Pluto, we believe Pluto also has an under-ice-crust ocean. And that means it there’s water there. We don’t know if that ocean connects to more ice. But we just have to go there and investigate it further.

Lindsay Hays:Chemicals, water, energy, time, it’s got a lot of really promising components. You know, I would say, “ever” is a long time, you know, so hopefully, yes, we will sometime go look at Triton to see what’s there. You know, it’s very far away. And as Jim said, there’s other targets in our solar system that are closer, easier to explore, because of just, you know, the vast scales of space in our solar system. But yeah, there, there are lots of things in our solar system that we’ve only begin to peek at. And I think there’s a lot to learn, you know, just within our neighborhood.

Elizabeth Landau:We also got some very interesting questions about the possibility of Earth life to go to other worlds. @VasudevR4385 asks, is it possible for us to survive beyond the Earth?

Lindsay Hays:yes, but you know, right now, humans need to bring our environment with us, you know, when it comes to, I was talking about extremophiles. And of course, that’s extremophiles, from our own perspective, right, things that live at hotter temperatures, or colder temperatures, those kinds of things. But we as humans are very sensitive, we have a very narrow range of conditions that we like to live at. And you know, in places that we’re able to bring our environment with us, bring our oxygen bring, you know, create the temperature that we like, bring our food, figure out either or, or figure out how to get, you know, the types of things that we need to consume — water, those kinds of things from the environment. We could, but certainly we don’t know of any place right now where the environments are suitable for human life, right on the surface of anywhere else.

Jim Green: Well, you know, from a human exploration perspective, Mars is really the most attractive target for us to be able to go live and work for long periods of time, and change the environment. Humans, humans are, you know, terraforming the Earth. And when we show up at Mars as humans, we’re going to be terraforming Mars. I mean, yeah, that’s what we call changing the environment, to, to be able to sustain our life as humans.

Jim Green: And so, we want to go to Mars, we want to be able to use the environment, so that means we’re going to be looking for water resources that are there. There’s plenty of water on Mars, it’s trapped in ice. But you know, we know how to extract it, and melt it, and use it. We would drink it. Of course, water is great for creating an atmosphere because you can break off the hydrogen and, and keep the oxygen and we need the oxygen, of course, that’s another critical thing.

Jim Green: And then water, if you break out the hydrogen and the oxygen, you know, water is H2O, we need one hydrogen, two oxygen, if you break it apart, you use that as rocket fuel, you know, hydrogen and oxygen can be used as fuel. Those are really essential features. And so, we would begin the process of using that environment to allow us to be able to live and work on the surface and survive.

Elizabeth Landau:And a related question, from @NideeshSooriya: “Can a seed germinate on any of the other planets?”

Lindsay Hays:You know, I think it’s kind of similar to the question about humans. Right now, we don’t know of any other place in the solar system where the native environment as it is, you know, you could just throw a seed onto the surface and they could really grow a seed long enough to grow into a plant. Mars may be a place where hardy microbes or tardigrades might be able to survive in the surface. And that’s part of the reason we have this whole group that works on planetary protection, to make sure that if we go to these places, you know, we are we and bring Earth life with us, you know, we we do it in a way that is careful and considered and you know, doesn’t do it accidentally and those sorts of things. So, you know, at this point, you know, Terran, life, life from the Earth, is very well suited to life on this Earth. And all of those different environments throughout the solar system are pretty different for, for the advanced life, like seeds and trees and people and things.

Jim Green: Yeah, I love that question. You know, it’s basically can plants grow with, you know, like on Mars? So, if you take a look at Mars, we know enough about Mars to really look at the essential plant nutrients. So, there are macronutrients in the soils like an oxygen, carbon, hydrogen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. There’s also micronutrients. There’s iron, magnesium, zinc, copper, molybdenum, boron and chlorine. So in reality, it’s got all the right stuff. The problem is, the temperature extremes are huge. So, in one day, the temperature will vary by 170 degrees Fahrenheit.

Jim Green:Okay, well, there’s no place on Earth that does that, you know, maybe over a year, we can see temperature extremes that are close to that on Earth, but, but not like that on a daily basis. So that makes it hard. And the other part of it is that the atmosphere is really thin. Now, that doesn’t mean we’re not looking at this idea. In fact, the University of Kyoto is a developing a chamber, that’s Mars-like in terms of its atmosphere. And, and, and actually trying to grow trees in that environment. You know, they’ve decided to look at sycamores. So, they’re overall taking that environment and lowering, lowering the temperature and see what it takes for the trees then to be able to, to live and, and grow in that environment. And so, this is a this is a research topic right now that is really important for us. Because if humans go to Mars, and therefore the temperature of Mars changes, we might be able to easily get into the temper, temperature regime where trees could grow, or other kinds of, of plant life.

Jim Green:Another idea is to take this fabulous substance called aerogel. It’s a series of silicon molecules that are connected in a very loose string. And it’s a great insulator, and if you put it down on the ground, you actually can keep the ground at a certain temperature without it going through these huge cycles too, and that might be an environment that you could grow grass or something else. So, these are all new ideas. These are things that are being tried. And I think over the next several years, we’ll get some exciting results from that.

Elizabeth Landau:That’s really cool. I hadn’t heard about the aerogel idea before. I’ve seen a little chunk of it at JPL. And it says it’s like more than 99% air.

Jim Green:Yeah, it’s, it’s what we call nanotechnology. And, and, and it is, it is, indeed, mostly air. But it is a substance that that is a wonderful insulator. We put it around our batteries to keep the batteries warm.

Elizabeth Landau:That’s awesome. Well, @Walker314159265, clearly a reference to pi, asks: “Of you find extraterrestrial life, will you report it publicly?”

Jim Green:NASA is not one to keep secrets. You know, we work really hard to have the public trust, that as we find out things, we want people to know what we have found out, it’s just really important for us to be able to communicate those results. The problem is, we need to communicate it in a way in particularly when they’re tough topics to talk about that, that everyone can understand them. Sometimes these things that we find out may seem what we call esoteric, you know that, that’s too hard to understand unless you’re really in the field. And, but they make progress, they keep moving towards answering that question. And, and make positive indications of environments and, and where life might, where life might exist. Sometimes, though, we, we get it wrong.

Lindsay Hays:Yeah, you know, I would say that the signs that we would be likely to find about, about extraterrestrial life, would really require the context. This is what we found, this is why we think, you know, it has no other explanation. This is why we think it’s quite obviously this. But it you know, it’s likely to be, you know, a squiggle on a graph somewhere, or, you know, something that seems out of place in some other observation. And so you have to really understand the whole observation and, you know, we need to find a way to communicate it, which is why we have fantastic science communicators at NASA, you know, it’s just as important at NASA that we have scientists and engineers as we do, people who help us explain what we’re doing to everybody else. And so, you know, I know I personally would be extremely excited about finding extraterrestrial life, it would be one of, you know, the height, certainly the highlight of my career to be part of, you know, to be part of NASA at that point.

Jim Green:Yeah, me too.

Elizabeth Landau:Absolutely. And I hope we get to see that. And a related question from @JTwinkie1: “If NASA did end up discovering intelligent life outside of Earth or even out of our solar system, how do you think that would affect us here on Earth?”

Jim Green: That concept of finding life and announcing it, intelligent life beyond Earth, it is one we would call a worldview change. When Copernicus came up with the concept, based on things that had been done in the past, but really putting things together and moving forward with the idea that planets go around the sun, and not the sun and all the planets going around the Earth, he literally changed the view, that worldview, that we weren’t the center of everything. So, it just was an incredible change that, that rippled through, you know, everything from religion to philosophy to science, and, and was an important new observation scientifically, that affected the world.

Jim Green:Finding life beyond Earth, in particular, extraterrestrial life that is intelligent, would be an enormous worldview change, you know. It will have the same effect.

Jim Green:Finding life beyond Earth that’s more microbial, which is what we expect in the solar system area, still will be an enormous worldview change, once again, taking the focus off the Earth of us being the only living creatures or beings, recognizing that there are other places that have life, changes that worldview. And the result of both of those will, will be astounding. You know, we will want to know, the next set of questions about what that life is like, what does it know? How can we communicate with it?

Jim Green:Whereas looking at this microbial life that’s living and growing in an environment that is evolved completely different from ours, they have evolved mechanisms to be able to live in those harsh environments, things that we would like to know how they do that, and therefore how we might be able to do that, if we’re able to crack that, if we’re able to crack the concept of being able to live and grow using, using new changes in our in our DNA structure that maybe other life forms have really done, then we can go anywhere in the galaxy we want to, I mean, it just opens up everything!

Lindsay Hays:As you said, microbial life is the thing we’re most likely to find within our solar system, intelligent life we may find outside of our solar system, which means the ability to communicate with that intelligent life may be low. You know, vast distances in the universe, make it hard to, to communicate, but, but you know, even seeing that it’s there, even knowing that it’s there, even sort of watching it from afar, I think can have a huge effect on, on a lot of wide ranging things.

Lindsay Hays:And, and the other thing I wanted to note is, you know, you were talking about microbial life, the potential for microbial life within our solar system. You know, I think whether or not that microbial life has a unique origin, right, a different origin from us, whether it’s a unique origin or whether or not it’s just like us, you know, we have the same origin of life as that life but broke off, you know, our distant cousins far back along with, you know, far back on our mother’s side kind of thing. There’s interesting things to learn either way, sort of, regardless of where of where we see that.

Elizabeth Landau: Absolutely. Well, I think that’s all the time we have for our audience questions. Thank you to everybody who submitted them on Twitter and Facebook.

Jim Green:Thanks so much, Liz, for all your effort on Gravity Assist. And behind the scenes helping her make it happen is Manny Cooper and Sonnet Apple, the fabulous audio and visual engineers that really, really make Gravity Assist so popular.

Jim Green:Well, this is the last episode of season four of Gravity Assist: The Search for Life Beyond Earth. And I want to entreat everybody to get excited about our upcoming season five, where we’re going to look at the new and exciting discoveries NASA is making, and also look at the engineering miracles of how we pull missions off. We’ll be interacting with scientists and engineers and if I’m lucky, maybe even pull in an astronaut or two. So, thanks again, so much, Lindsay, for all your help in answering these fabulous questions on Gravity Assist.

Lindsay Hays:Thanks again, Jim, for having me.

Jim Green:I’m Jim Green, and this is your Gravity Assist.

Credits:

Lead producer: Elizabeth Landau

Audio engineer: Manny Cooper