Europa Clipper's Voyage to Jupiter's Ocean Moon
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Arching under the night sky, inky with black expansiveness, a NASA probe is sailing to the outer solar system. The mission is called Europa Clipper. Its target, Europa, is a moon of Jupiter just smaller than our own moon. Europa is covered in a sheet of ice that is miles thick, like something from a sci-fi movie. If we were riding along with Europa Clipper, at first glance, this moon would seem to have nothing in common with Earth.

You're far away and you see just this white globe of ice. And as you get closer and closer and closer, you see all of these fractures and furrows that are crisscrossing the surface. And you notice that these fractures and furrows are this reddish brown color. Lene Quick-Henderson is a planetary scientist at NASA who studies ocean worlds. She spent a lot of time looking at Europa's surface.

For one, as you probably guessed from the ice, it is cold. About minus 225 degrees Fahrenheit on what counts as a hot day. And then there are those features that Lene calls fractures and furrows. They look like long scratches, almost like a giant dragged its fingernails across Europa's surface. Those are cracks in the ice. I think about when these fractures are forming on the surface. Does the surface shake? Do we have Europa quakes? You know, we probably do.

If you and I were standing on the surface miraculously and surviving, what would that be like? It would be frigid, first of all. We'd have to have the heaviest winter coats that would ever exist. But we'd see...

Mountains, these ridges would look like that I'm talking about that look like fractures and furrows from far away up close would probably look a lot like mountains do. And we might see a geyser erupting in the distance. We might see the icy particles and the water vapor spraying up over the surface of Europa. Did you catch that last part? Water. We might see water. Miles beneath its icy surface, Europa appears to have an ocean of liquid water.

Now it's time for Europa Clipper to answer our next question: Could Europa also have the right conditions to support life? This is NASA's Curious Universe. Our universe is a wild and wonderful place. I'm your co-host Jacob Pinter. In this episode, NASA is working on one of the biggest questions there is: Does life exist beyond Earth? We're still looking for the answer, but there are places worth searching in our own backyard.

We'll fly along with Europa Clipper and learn how NASA hopes to prove that this moon holds the ingredients that could make life possible. Also, Europa Clipper is a sort of message in a bottle, bridging the gap from one ocean world to another. Onboard the spacecraft is a new poem by Ada Limón, the US Poet Laureate. Ada will explain how she turned a NASA mission into art and why it's important for space nerds to step back and feel connected to the universe and to each other.

One of Linnaeus Quick-Henderson's job titles is Planetary Geologist. And when your business card says Planetary Geologist for NASA, you get a lot of invitations to tell kids how they too can become scientists. People will invite me to come talk to kids, especially little girls, and say, and if you have any pictures of you in your rock collection when you were a little girl, bring them. And I'm like, great, but I don't have any. As a child, I did not have any.

think that I wanted to become a scientist. Back in North Carolina, Linnae's family was full of teachers and professors. And she saw herself following in their footsteps, teaching English somewhere. But there was one high school science class that changed her mind. For the first time, she studied astronomy. And she also learned some people get paid to do that.

My senior year in high school, my physics professor, knowing that I was kind of on this track, had Dr. Reva Williams call me. And Reva Williams was, she's considered to be the first African-American woman to get a degree in astrophysics. And so that was a big deal for me. I don't know how he found her, but she called and she talked to me and she said, you know, if you really want to do this, you're going to have to get a PhD and it's going to take X number of years, which at the time scared me very much.

Because it seemed like it was going to take forever. But something that she told me was, you know, the time is going to pass anyway. So you might as well be working towards a degree to do what you love. When Linnae was a graduate student, Europa entered the picture. Linnae was looking for a summer internship. She sent emails to astronomer after astronomer asking, do you have any openings? I cold emailed. I guess this was my cold email phase of life. Finally, she landed at Johns Hopkins University.

For people who are old enough to remember, we took the type of clear paper that we used to put on overhead projectors. Yeah. Got a big piece of that. Kids these days don't know. Kids these days don't understand the power of the overhead projector, but took a big piece of kind of like overhead paper, overlaid it on a printout of Europa's surface, and then took overhead projector markers and kind of mapped and traced different features on Europa. And that's how I learned to map.

And it was totally different. It was something that I'd never done because I was a physics major. So I was used to math and equations and all of these things and just looking at a new world and drawing the geological features or tracing rather the geological features when I'd never even taken a geology course. I completely fell in love with it. Now, Linnaeus was not the first person to be fascinated by this moon. Humans can see Jupiter with the naked eye. So we've been tracking it for thousands of years.

More than 400 years ago, when the astronomer Galileo Galilei took his homemade telescope for a spin, he discovered four moons orbiting Jupiter. Now picture, if you will, a fantastic world where not one, but 12 moons crisscross the sky. Today, we still call those the Galilean moons, and one of them was Europa.

In the 1970s, NASA sent humanity's first probes ever to the outer solar system. And we started learning just how complex and interesting those moons are.

First, a couple of missions called Pioneer 10 and Pioneer 11 flew past Jupiter for the first time. Late November 1973, 20 months after launch, Pioneer 10 closes in on Jupiter. Each hour brings the planet 20,000 miles closer. A few years after that, we reached Jupiter again. On their journey to the edges of the solar system, the Voyager mission sent back images of Jupiter's Galilean moons.

For the first time, we could make out surface features on Europa, although we couldn't tell just how rough the icy terrain was. Ganymede, etched by icy parallel grooves. Europa, smooth and icy. And Io, glowing a cold... Things really kicked into gear in the 1990s and early 2000s. That's when we got our best view of Europa to date.

It came from a mission called Galileo, named after that groundbreaking astronomer. And can we just take a moment to appreciate the Galileo mission? Not only did this spacecraft make it to Jupiter, it dropped a probe into Jupiter's atmosphere. As it fell, that probe felt temperatures twice as hot as the surface of the Sun, and atmospheric pressure 23 times greater than Earth. And it still sent back data for us to analyze.

After that, Galileo performed a series of flybys past Europa and other moons. The pictures from Galileo are the most high-resolution images we have of Europa, at least until Europa Clipper gets there. When I brought Linnae into our studio, I showed her a picture of Europa on a computer screen.

I was looking at the description as I pulled this up, and I want to say this is from the Galileo mission. That is from Galileo. Can you tell? Like, just by the picture, you know this is Galileo. This is a different mission. Well, sure, because of the image resolution. Plus, I spent my whole dissertation looking at images of Europa from the Galileo spacecraft. So, yeah, this is Galileo. So what do those images tell us about Europa so far?

Well, it's clear that Europa's surface is a layer of ice. And there are those fracture marks lining the surface, evidence that the ice sheet churns and sometimes breaks apart. In some places, the landscape is so gnarly that scientists call it "chaos terrain." Even though we've never seen what's underneath Europa's ice sheet, we're pretty sure we know what's there.

Galileo did more than take pretty pictures. Spacecraft can send us back data on a planet that helps us determine what's in the planet or moon's innards. It helps us determine the density. Galileo carried several instruments that helped us look inside Europa. First, there's the surface layer of ice. It appears to be 10 to 15 miles thick, or about the height of two Mount Everest's stacked on top of each other.

Based on how dense Europa is and how it conducts electricity, an ocean of salty liquid water is the best explanation for what's underneath the ice. In fact, even though Europa is smaller than our moon, it probably has more water than all of Earth's oceans combined. On Earth, the deepest point in the ocean is almost seven miles beneath the surface.

But Europa's ocean could be anywhere from 40 to 100 miles deep. You could probably look down into a crevice and see part of Europa's interior, but that's where the ocean comes up. And it deposits this material onto the surface, not only water, but salts and mineral acids. On the surface, mixed in with the ice, we've detected different kinds of salts. There's magnesium sulfate, which you know as Epsom salt.

Sodium sulfate, an ingredient in laundry detergent, and even sodium chloride, aka table salt, the same kind that's in your pantry. But before you sprinkle Europa salt on your lunch, consider that those salts have also been blasted by radiation from Jupiter and turned a yellow or reddish-brown color. So it's interesting to think about how Europa might smell when you think about that. Europa has bizarro versions of some other processes that we recognize on Earth.

Lene's specialty is studying volcanic activity. In Europa's deep freeze, it's called cryovolcanism.

Cryovolcanism is cold volcanism. Instead of having molten rock erupting, we have water and ices and water vapor and salts erupting. We have images where it looks like we've had some sort of liquid flow across the surface of Europa. And so we believe that those are cryolava flows, probably just flows of water and salts. We also have explosive cryovolcanism, where we have

ice and water being kind of thrown onto the surface. These explosions are called plumes, and the water vapor exploding up, it comes from Europa's ocean. At the moment, we don't know of any water plumes on Europa's surface. But in the past decade or so, the Hubble Space Telescope has seen evidence that they exist, maybe just for short periods of time.

I'd say if we've all seen images of old faithful geyser on Earth. And so probably like a ginormous old faithful, but a lot of icy particles, not just water, but icy particles and much taller, much taller. Like the Clipper ships it takes its name from, Europa Clipper will zip through space. It carries cameras and high tech science equipment, which will build on previous missions like Galileo.

Europa Clipper has nine different science instruments, including a high-tech radar and a magnetometer. Plus, another experiment that studies gravity using the spacecraft's communications system. There are two cameras on board that take pictures in visible light, not so different from the cell phone camera in your pocket. There's one for wide-angle pictures and one for close-ups. We have to get the whole picture of what we're looking at, but you also want a camera that can look up close so that we can see the smallest details of the surface.

Is there one area on Europa that you personally want to see the most? If there are plumes, I want to see those the most. Now, this spacecraft will not land on the surface of Europa. It has a complicated orbit that accounts for the gravity of Jupiter and its other moons. But as Europa Clipper flies past Europa a total of 49 times, swooping just 16 miles above the surface, it will collect gas and dust floating up above.

It has instruments that can analyze those particles to figure out what they're made of and how they got there. If Linnaeus gets her wish and Europa Clipper does see a plume, the spacecraft might be able to fly through the plume. That would give us a chance to sample water directly from Europa's ocean. All of this data goes back to the big question.

Since Europa is an ocean world like our own, could it also support life? What we're trying to determine with Europa Clipper is whether or not conditions could be favorable for life to be there. Now, we need to make something really clear. Europa Clipper is not looking for life. Even if Europa does have life, this spacecraft is not equipped to find it. We want to know, does Europa have the right conditions for life?

And so far, things are looking good. The basic building blocks of life as we know it are: First, water. Check. Second, energy. Throughout Europa's orbit, the gigantic gravitational force of Jupiter causes Europa's insides to flex. If you've ever smooshed a stress ball over and over and felt it get warm in your hand, that's basically what Jupiter does to Europa. So, energy. Also check. And third, you need the right chemical building blocks.

We strongly believe we have the liquid water. We know we have the energy. That's two out of the three. And so we need to establish whether or not we have that chemistry and establish how the geological processes on Europa might stir that liquid water and that energy and that chemistry to make it a habitable world. Like most NASA missions, it's going to take time before we get the big answers. Linnaeus and other team members have poured years of their lives into this.

And after Europa Clipper lifts off from the coast of Florida, it takes about six more years to fly all the way to Jupiter.

I've never been to a launch. I'll probably cry. I don't know. I guess I had no concept of when I first got into planetary science and decided I wanted to focus on planetary science. I would be working on one project for 10 years before launch even happened. And by the time we get data, it'll be 16 years total. I just didn't think about that. It seems like it's been a long time coming. So I will be ecstatic.

In the meantime, NASA is planning other ways to keep looking for life, even if it looks more like single-celled bacteria than little green men. Linnaeus also works on an upcoming mission called Dragonfly. Dragonfly will land a type of drone helicopter on a moon of Saturn because it appears to have some of those building blocks for life.

And NASA's taking the first steps toward building the Habitable Worlds Observatory, a space telescope designed to look for signatures of life on planets outside of our solar system. Linnaeus says Europa has taught us that when we look for habitable worlds, we shouldn't necessarily look for clones of Earth. You know, I understand why we want to look for other Earths, but could we look for other Europas? Our own solar system teaches us that we can find habitable environments

pretty far away from our own home star. There have to be other places like it in our galaxy. With Clipper, with Dragonfly, with other things NASA is doing, you know, we're kind of chipping away at this big question, is there life out there somewhere? Sure. Which is like one of the big questions that's left. What does it feel like to be one of the people chipping away at that question?

You know, I guess that's something that I don't always think about either. I mean, having been trained to be a geophysicist, I really tend to focus on what geology we might see at the surface. But one thing that I do think about in doing this geology is that when you think about these icy moons or these ocean worlds,

Really, I think the geology and the environments for life are tied together. You need these geological processes to stir things together, to make conditions ripe for life. I also think about how Earth-like some of them are. I mean, Europa, if you take away the icy shell, is very much like Earth. As Europa Clipper travels hundreds of millions of miles toward Europa, it carries a message from Earth to another ocean world. More than two and a half million people signed up to have their names aboard.

Each name is stenciled in teeny tiny letters onto a microchip the size of a dime. The spacecraft also carries the Drake equation, a famous thought experiment to estimate the chances of finding alien life. And etched into one of Europa Clipper's metal plates is a poem. It's called "In Praise of Mystery: A Poem for Europa" and it's written by Ada Limon, the US Poet Laureate. In fact, the poem is etched onto the spacecraft in Ada's own handwriting.

I had a chance to talk to Ada to learn how this poem came together. And she says it all started in the fall of 2022. She was a few months into the job, still settling in as poet laureate, when NASA set up a meeting. And we asked Ada, would you be willing to write a poem inspired by Europa Clipper?

We sat around and listened to the many different aspects of the mission. And as someone who loves space and thinks a lot about the planets and our place in the universe, I said yes very quickly and then immediately was terrified with the idea of writing a poem. Why were you terrified? Well, you know, my enthusiasm is...

both a blessing and a curse, as they say. And one of the things about this particular request was that I thought, wait, how am I supposed to make a poem that speaks for the earth, that speaks for all of us here? That was very honestly the hardest prompt I've ever received in my poetry life.

So you have this first conversation with NASA. I'm curious what you knew about Europa at that point at the beginning. Like, did you even know what Europa was or where it was or anything else? You know, I had heard of it, but I hadn't done much research. And so when they were presenting the mission, I was really fascinated to know more about Europa and

that it might have all of the ingredients for life, the idea of this icy layer, a moon that's primarily water. So many facts about it are incredibly fascinating and you quickly see why so many people are interested in Europa. Do you have the poem In Praise of Mystery with you? I do. And would you mind reading it for me? Sure. In Praise of Mystery

A poem for Europa. Arching under the night sky, inky with black expansiveness, we point to the planets we know. We pin quick wishes on stars. From Earth we read the sky as if it is an unerring book of the universe, expert and evident. Still there are mysteries below our sky.

the whale song, the songbird singing its call in the bow of a wind-shaken tree. We are creatures of constant awe, curious at beauty, at leaf and blossom, at grief and pleasure, sun and shadow. And it is not darkness that unites us, not the cold distance of space,

but the offering of water. Each drop of rain, each rivulet, each pulse, each vein. Oh, second moon, we too are made of water, of vast and beckoning seas. We too are made of wonders, of great and ordinary loves, of small, invisible worlds, of a need to call out.

Through the Dark. It may have been a challenging assignment, but it's a lovely poem. Thank you so much. I'm really quite happy with how it turned out. I struggled with many, many different drafts, maybe 19 or 20. And when it finally was finished, I thought, oh, right. It needed to be a poem that, yes, went outward, but also came back to this earth.

After spending 19 or 20 drafts on it, now when you read it, are there any lines or turns of phrase where you get to it and you think, oh, yeah, that's a good one. I'm glad I did that. I don't really have that moment, which I love that you asked. But I do have a moment where poems shift, you know, depending on what's going on in your life or what's going on in the world.

And so there are times when I read the poem and certain lines get highlighted or come into the forefront.

because of what's going on. So just now, as I read that poem, I thought about the "it's not darkness that unites us." How so many things can feel so separate and we can feel so bifurcated as human beings on this planet. And of course the line is speaking to both Earth and Europa, but it is also speaking to us, those of us who live here on this Earth.

I watched the event where you presented this poem in public for the first time. And at that time, you said that there was one line that you jotted down during your very first call with NASA. Yeah. And that line survived all the way into the final draft. Yeah. Which line was that? We too are made of water. Huh. Yeah.

I have it. It's interesting. I have it in my notebook. I keep a very, I don't want to say meticulous because I don't think I'm very meticulous about anything, but I keep a daily journal that I carry with me wherever I go. And it has everything from my grocery list and my to-do list to drafts of poems, to notes, to meetings. And in that initial call where I'm writing something,

notes about Europa, I write the line, we too are made of water.

So the line that I wrote down I was going to ask you about is, Oh, second moon, we too are made of water, of vast and beckoning seas. And I was really curious, you know, we obviously at NASA have so much information about Europa. And I was just wondering if there's a way you can give me a window into how you take those facts, that information, and turn it into this piece of art. And like...

What connection are you trying to make between Earth and Europa? I love that you asked that because one of the jobs that I had to do, and that was actually quite difficult for me, as a curious person, I love to find out facts, right? But as an artist, once you have those facts, you have to let them go. One of the reasons that the early drafts of the poem failed was

or just weren't working was because I was trying to make them about facts. Like you said, we have all these facts about Europa. We know all of these things. And what I had to do was let that go. I couldn't talk about the icy layer, right? That's miles deep. I couldn't talk about, you know, this level of what we think this water substance is.

I couldn't talk about those things because that's actually not what the poem wanted to do. Writing the poem is very interesting because you take all this information in and then you release it and see how it speaks to you on a more emotional, textural level. And so with that line in particular, it's,

I thought, okay, I'm just going to go with oceans and seas, vast and beckoning seas. So at one point you were literally trying to work in the thickness of the ice or the composition of the water or things like that? Yes. I remember them feeling very much like they were interested in educating themselves.

And it turns out poems have no interest in doing that. They really don't. Like poems, you know, I think poets love facts, but poems don't. When I was first writing those poems, I think I was thinking, oh, how do I tell people about Europa? And in reality, that wasn't my job, nor was it the job of the poem.

Throughout this process, you were able to visit NASA's Jet Propulsion Laboratory and see Europa Clipper while it was being built. Tell me about that. Like, what did you see? What did you learn? And what did it feel like to be so close to this actual spacecraft? Oh, it was incredible. I think a lot about how many people it takes to make anything. Even as a person who writes poems, I can say, oh, I write it by myself. But in reality, everyone who's ever written a poem writes

and come before me is there in the room when I'm writing a poem. Anyone who's ever given me advice, any teacher I've ever had, any friendship, any kindness shown to me, all those things are part of why I write and how I write and who I am. And I think that that really comes into fruition when you see something like the Europa Clipper actually being built in the clean room. And that was really incredible to think about just the great

human endeavor that is building something, making something that will go on this incredible journey. I've seen pictures of the vault plate that is installed on the spacecraft now. It has the poem in your own handwriting etched into it. What does it mean to you that a poem you wrote in your own handwriting is going to be onboard this spacecraft headed to a completely different world?

It's very overwhelming. I actually didn't know that it was going to be engraved in my own handwriting. And can I just say that my grandmother died about a year ago. And when I see my handwriting, I think about how during the summer she taught me

how to correctly make my cursive A's and my cursive B's and her patience with me. And so that is part of it, is that I think it's not just me, but my grandma. And that's really sweet to me. And the other part of it is that it does feel really human. I'm really glad that it's not a font. I'm really glad that it's not AI.

I love that it's a human hand that wrote it. I think that's the way I think of it. I think if I think too much of it as my own handwriting, I can get a little panicked. But if I think of it as just human, that to me, that delights me.

This mission and, you know, incorporating a poem and Frank Drake's equation and things like that, it makes me think of Voyager with the golden records. Hello from the children of planet Earth. A message from humanity to the rest of the universe. Was that something that was on your mind during this process? And if so, how did you use that as a reference point?

Yes, you know, I was thinking a lot about that and I was thinking about how the sound of the human heart is on the golden record. And it's the heartbeat and it's a heartbeat in love. And I thought maybe there was a way to make the poem really also include that heartbeat and that breath.

Here at NASA, science is what we do, discovery is what we do, like, we're going to keep doing that. As we are exploring, why is it important that we make room for poetry along the way? One of the things that poetry allows for us to do is to explore our own emotional inner worlds. And I think very often we can get caught up

on our own intellect and think about, oh, I need to know this. I'm curious about this. What proves this? What disproves this? And all of that is so useful and wonderful and necessary. And yet we also need to process how we feel about it. And I think there are times where if you work with a scientist, let's say, who study trees, you know, they can think very deeply about

how a tree works and behaves. And yet at some point it's very useful to walk into the forest and just feel what it is to be connected in a forest. I think that it's important that we don't lose sight of that. It's important that we understand the why and we understand our need for our own human connection, not just to each other, but to the planet, to the universe.

We have a question that we ask to everyone who comes on this show, since the name of our podcast is Curious Universe. What are you still curious about? Oh, what am I not curious about? You know, I love this question. I have so many people who say, how do you find ideas for poems? And I think I am endlessly fascinated by being alive. I love to think about animals and

and their behavior and what they're thinking. I don't know if you can hear my little beautiful pug snoring next to me. And I think, you know, what is she dreaming about? I'm endlessly curious about the natural world, but I love thinking about the emotional life of animals.

Ada Limon is the US Poet Laureate and she wrote the poem "In Praise of Mystery: A Poem for Europa." Ada, thank you for the poem and thank you for making time for this. It's really been a pleasure. Thank you so much for having me. The first opportunity to launch Europa Clipper will be on October 10th. You can watch the launch on NASA+ with broadcasts in both English and Spanish. That's plus.nasa.gov, our streaming service which is completely free. After that, you'll have to be patient.

Europa Clipper will arrive at Jupiter in 2030, and it makes its first flyby of Europa in 2031. You can see more about the mission, including Ada's poem and ways that you can get involved, at europa.nasa.gov.

This is NASA's Curious Universe. This episode was written and produced by me, Jacob Pinter. Our executive producer is Katie Konins. The Curious Universe team also includes Christian Elliott, Mattie Olson, Michaela Sosby, and of course, Patti Boyd. Christopher Kim is our show artist. Our theme song was composed by Matt Russo and Andrew Santaguida of System Sounds. Special thanks to Lawrence Fokene at NASA's Jet Propulsion Laboratory.

We had research help in this episode from Michael Chesnis, a science librarian with NASA Communication Services, and April Gage, senior archivist at NASA Ames Research Center. If you want to learn even más about Europa Clipper, we also have an episode of our Spanish-language podcast, Universo Curioso de la NASA. And you can find all of our shows at nasa.gov slash podcasts.

As always, if you enjoyed this episode of NASA's Curious Universe, please let us know. Leave us a review, share the show 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. I'm so excited. I was wearing my NASA shirt today. This is an official NASA podcast.