Consider This from NPR - Are We Alone In The Universe?

Episode Date: March 1, 2024

Are we alone in the universe? It's a question that's been posed again and again. Carl Sagan posed it in the 1970s as a NASA mission scientist as the agency prepared to send its twin Viking landers to Mars. And nearly 50 years after the first of two landers touched down on Mars, we're no closer to an answer as to whether there's life — out there.Scientists haven't stopped looking. In fact, they've expanded their gaze to places like Saturn's largest moon, Titan and Jupiter's moon Europa. The search for life beyond planet earth continues to captivate. And NASA has upcoming missions to both moons. Could we be closer to answering that question Carl Sagan asked some 50 years ago? For sponsor-free episodes of Consider This, sign up for Consider This+ via Apple Podcasts or at plus.npr.org. Email us at [e-mail] more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy

Are we alone in the universe? That question took on new meaning in the mid-1970s as NASA prepared to send its twin Viking landers to Mars. Is life everywhere? Mission scientist Carl Sagan speculated on what Mars might have to teach us in a NASA documentary previewing the mission. Well, there's no way for us ever to answer that question except by looking for life elsewhere.

And the nearest candidate planet is surely Mars. The documentary also featured some more imaginative musings about what the landers might discover. Life forms on Mars may have silica shells to protect them against the radiation. I can even imagine forms of life having leaf-like structures, oriented by the sunlight, possibly of unusual colors. Another solution to the problem of water might be an organism that eats rock.

Well, in July 1976, Mars fever grew. When the first of the two landers touched down on the red planet, we ran near daily dispatches on all things considered. Viking biologists have announced observations that might imply the presence of life on Mars. There could be algae growing on the rocks. Some of the rocks could actually be turtles. Some of the little dots at the limit of resolution could be insects. I don't know what a Martian looks like. Do you? For National Public Radio, this is Jim Loudon at Viking Control, Jeff Propulsion Laboratory. Nearly 50 years later,

after legions of orbiters and rovers and landers, we still haven't found any conclusive evidence of life out there. Not that scientists have stopped looking, but they have expanded their gaze to places like Saturn's largest moon, Titan, with its rich stew of organic compounds, the building blocks of life. They've also set their sights on Jupiter's moon, Europa, with its salty ocean locked beneath an icy shell. If we've learned anything from life on Earth, it's that where you find the liquid water, you generally find life. These worlds are incredibly compelling from the standpoint of our search for life beyond Earth. Consider this. The search for life beyond planet Earth continues to captivate. And NASA has upcoming missions to both moons.

Could we be closer to answering that question Carl Sagan asked some 50 years ago? From NPR, I'm Mary Louise Kelly. It's Friday, from NPR. The search for life elsewhere in our solar system has captivated science fiction writers. You can see the thick orange atmosphere rolling off the USS Enterprise in Star Trek. And Titan is the homeworld of Marvel supervillain Thanos. Titan was like most planets. Too many mouths, not enough to go around. The latest journey to the final frontier is pushing towards the outer reaches of the solar system with two upcoming missions to moons of Jupiter and Saturn. Catherine Nish of Canada's Western University is on the team for NASA's Dragonfly mission,

which heads to Saturn's moon Titan in 2028. And Kevin Hand at NASA's Jet Propulsion Lab is working on Dragonfly and the Europa Clipper spacecraft, which blasts off to Jupiter's moon Europa in October. With that mission coming right up, I asked Han to tell me why this icy moon is so intriguing. Europa has this ocean of salty liquid water beneath this ice shell that's about maybe 10 or so kilometers in thickness. We really don't know. And if we've learned anything from life on Earth, it's that where you find the liquid water, you generally find life. And so worlds like Europa and that harbor liquid water oceans out there in our solar system today, these worlds are incredibly compelling from the standpoint of our search for life beyond Earth. Even if they're under, you just described kilometers of ice on top. That's a lot of ice.

That's right. These are dark oceans. And so photosynthesis, as we know it here on the surface of the Earth, is probably not really a viable energy pathway. Instead, if there is life in these oceans, it's probably sustained through chemical reactions that can power life. Similar, perhaps, to what we see in the deep, dark depths of our own ocean. Places like hydrothermal vents where microbes and other organisms just chew away night and day without any knowledge of the sun above.

And one more to you, Kevin, because I'm told engineers have just finished loading the scientific instruments onto the Europa Clipper in preparation to launch. What specifically are y'all going to be looking for? You get there in 2030, is that right? Yeah, about that time frame. It launches, knock on wood, in October. And once the spacecraft is there, the payload is designed to assess the habitability of Europa. It'll have cameras that can take images of the surface, spectrometers to tell us about the chemistry of the surface and any materials coming off of the moon. And then we've also got an ice-penetrating radar that will allow us to see within the ice and potentially even to the ocean below. Okay, Katherine, jump in here because I want to turn to this other really intriguing moon. This is Titan, Saturn's moon. It might also have a subsurface water ocean like Europa, but I'm told it also has seas of liquid hydrocarbons, things like methane, on the surface.

Help me picture that. That's right. Titan is unlike any icy world in the outer solar system because, unlike most icy worlds, it has an atmosphere. An atmosphere that's not dissimilar to Earth's, made primarily of nitrogen, but it also has methane. And at the low temperatures that we find on Titan, that methane can actually act as a liquid. So we see lakes, we see streams, we see all the same erosional patterns we see on Earth. It's just the materials are all different. So the Dragonfly mission, which I gather if all goes well, will arrive and start hopscotching around the surface of Titan in the mid-2030s. What are you

hoping specifically to learn? One thing we think is happening on Titan is that the organics that are formed in its atmosphere, because of the presence of nitrogen and methane, rain down on the surface. And then once they're on the surface, they can mix with these transient liquid water environments we think are there in the bottom of impact craters. And if you mix those two ingredients, carbon-containing compounds and water, that's very similar to what we think the origins of life look like on Earth. So we're really hoping to see maybe the starting point of life happening on the surface of Titan, which we can then sample with Dragonfly.

So this prompts a question to both of you, because you've both been describing on two different moons conditions that possibly could support life, but it sounds like very different conditions, totally different than we have here on Earth. Does that mean there's the possibility that these seas would support life as we don't know it, life that looks nothing like what we would recognize as life here on Earth? So that's certainly true for the methane oceans on Titan. If there is any life there, it is going to be completely different than what we see on Earth. Because unlike life on Earth, which uses water as a solvent, if there was life in the oceans on Titan, that would use methane as

a solvent. So completely different. And I'm not even sure we're clever enough to search for that life. It would be so alien to us. That's the thing. Like, would we even know if we found it? That is a concern of mine, for sure. Kevin, what do you think? Life as we know it, life as we don't know it, would we even know it if we find it? Yeah, well, part of the way that the spacecraft and the instrument payloads are designed is to have the opportunity for discovery-driven science. Finding things that we can't really predict are out there. And Titan is just such a wonderful world in this context. Because, like Catherine said, it's a great place for life unlike life as we know it.

I mean, I suppose this prompts me to ask how hopeful either of you are. My editors here are reminding me that we've been hunting for life elsewhere in the solar system for decades. They were reminding me back in the 1970s, the Viking 1 and 2 missions landing on Mars. Have all of the intervening years tempered your expectations at all about our ability to find life elsewhere in the solar system? Kevin, you first. Well, I guess first I'll say this business is not for the faint of heart. It's a generational endeavor. And while we have been exploring the solar system for roughly 60 years or so, we really have not sent that many spacecraft beyond the asteroid belt. And so this type of exploration is really just beginning.

Katherine? I think if we're going to find life anywhere, it's going to be within our own solar system. And this is the whole reason I became a planetary scientist. However, in the 20 years I've been in this field, I think I've become a little bit more pessimistic about our options here. And that's because in addition to water, which Kevin has brought up, life also needs carbon. And in so many places in the solar system, we find one or the other, but not both. So we really need to focus on those areas where we have all the ingredients you need for life together in the same environment. And I'm hopeful we can find those environments, but I think they're not as numerous as I originally hoped.

Catherine Nish of Western University in Canada and Kevin Hand, director of JPL's Ocean Worlds Lab. This episode was produced by Kai McNamee and Brianna Scott. It was edited by Christopher Intagliata. Our executive producer is Sammy Yenigan. And thanks to our Consider This Plus listeners who support the work of NPR journalists and help keep public radio strong. You can learn more at plus.npr.org. It's Consider This. From NPR, I'm Mary Louise Kelly.