The most exciting interplanetary mission for the early 21st century is arguably not a robot named Perseverance currently roving around Mars gathering samples for a future return to Earth. Instead it is a NASA spacecraft that could launch later this decade to Europa, an enigmatic moon of Jupiter that boasts an enormous ocean—bigger than all of Earth’s oceans combined—beneath an icy crust. Called Europa Clipper, the mission could lift off as soon as 2024 to study the moon’s subsurface abyss with the goal of gauging its potential habitability and the distinct possibility of discovering a “second genesis” there. Many astrobiologists consider Mars to be a prime target for seeking out signs of ancient, now extinct extraterrestrial life because of its relatively Earth-like conditions billions of years ago. Europa, in contrast, has never really been like Earth at all, but it still may offer the solar system’s best prospects for harboring alien organisms that are alive right now.

That makes the central narrative of David W. Brown’s 2021 book The Mission: A True Story all the more intriguing. Despite the overwhelming scientific and popular appeal of sending a spacecraft to look for life within Jupiter’s watery moon, the quest to make Europa Clipper a reality has been a decades-long uphill battle. The fact that the mission became NASA’s next great planetary science project—and that it even exists at all—is a triumph over what, at times, seemed to be insurmountably long odds. Brown, a Louisiana-based journalist, spent several years following the key scientists, engineers, bureaucrats and politicians behind the mission. The result is a definitive account of Europa Clipper’s inception—and of the often heroic and sometimes tragic human struggles behind each and every robotic emissary sent voyaging to worlds beyond.

Scientific American spoke with Brown about his book, Europa Clipper’s long journey to the launchpad, the reason Mars is the “Death Star” of planetary science, and more.

[An edited transcript of the interview follows.]

First off, I want to commend you: I’ve followed this topic for years, but I still learned an enormous amount by reading your book. By focusing on the people and the politics behind Europa Clipper, you’ve revealed the many other dimensions outside of science that must come together to make interplanetary exploration happen. I think there’s an enduring value to your work here, in a historical sense, that goes beyond just telling a good story.

I’m humbled. Thank you very much.

You’re welcome! What I’m getting at is that one could say The Mission is not really about going to Europa at all because you’ve written and published it well before the spacecraft even reaches the launchpad. What would you say it’s about?

Thematically, this book is about how different people handle crossroads in their lives. Each of the characters, early on in his or her career, has some moment, some decision point, where things could have gone either way.

Consider the case of Louise Prockter, for example, who is now chief scientist of the Space Exploration Sector at the Johns Hopkins University Applied Physics Laboratory and was a crucial early contributor to Europa Clipper. She didn’t travel through the typical grade-school-to-college-degree pipeline that most people in the field did. She was an adult with a career when she decided to make a life change and pursue a university degree. And she would go on to become one of the most important researchers in all of planetary science. Bob Pappalardo, the project scientist of Europa Clipper, throughout his career, could have, at any time, put the Europa project aside—it would have been the smarter move, professionally. But something in his character wouldn’t allow him to do that. He had to get a mission flying. At NASA headquarters, Curt Niebur’s job as a program scientist in the planetary science division would have been so much easier if he had just marked a clean line across Europa in his portfolio and said, “Next,” but he didn’t. And this goes down the line for every character in the book.

It also applies more broadly to NASA and even the field of planetary science as a whole. Institutions and communities have had to make hard decisions in terms of exploration priorities and how to handle the perennial financial maladies that come from pursuing pure science. All of these things, and many more, ultimately came together to yield admission to Europa. Any single element that had gone the other way might have derailed the entire project.

What inspired you to approach this subject in the first place?

The initial spark of a book emerged from a realization that after New Horizons flew by Pluto and after the planned conclusions of the Cassini mission at Saturn and the Juno mission at Jupiter, humankind would not have any active spacecraft exploring planets beyond the asteroid belt. The outer solar system would go dark for the first time since the 1970s.

Humanity was going to lose something important when that happened. And it bothered me a lot—as an American, as a human being who sees our possible future on other worlds and as someone interested in science. You know, other than war, it sometimes seems like space exploration is the only sort of human endeavor where the pronoun used is always “we”: We go to war. We landed on the moon. And whenever that endeavor is diminished, I think it’s a loss for all of us.

At the time, Europa exploration was not much more than a series of studies. But it was obvious to me and so many others that it was our best hope for rekindling exploration of the outer planets—to say nothing of its implications. I mean, as a storyteller, you’re always on the lookout for high-stakes narratives. And certainly, if, in fact, life is one day found in the oceans of Europa—and conceivably complex life—I mean, that would have implications for science, philosophy, religion and of course geopolitical priorities. It would be a galvanizing moment in human history. And I hoped desperately that there was a story there.

The first person I spoke with was Louise Prockter, who told me she had 15 minutes to talk. And I said, “That’s great. That’s all I need.” Three hours into the 15-minute conversation, I realized that after a decade of her working on one Europa study after another, this was probably the first time she had really opened up with any journalist about this amazing thing she was a part of and that had become a part of her.

And that seemed true for everyone who was part of the Europa mission. They fought in the trenches for so long to get this thing going. The more people I spoke with, the more I learned about the struggles and the setbacks, the heartaches and the loss, and the sheer adventure of it all. I fell in love with everybody in this book and with Europa. And, really, I fell in love with the whole field of planetary science.

I recall talking to you a little about this book a few years ago, and at the time, the tentative title was One Inch from Earth. Now, of course, it’s The Mission (with a beautiful and elaborate subtitle). But as much as I love its current form, I’m a bit disappointed I never got to learn the meaning of the book’s original title. What was that about?

I was attending an early test of the engines that are going to go into NASA’s Space Launch System (SLS) rocket, which was originally intended to send this spacecraft to Europa. Todd May, who was, at the time, head of the SLS program, gave a brief talk about the process of bringing the rocket—or a mission—to the launchpad. And he said that flying a spacecraft three billion miles is easy. It’s getting it one inch off the launchpad that’s hard. And he’d meant that both on a technical level and also programmatically. It is very difficult to get these missions going, and I think most people don’t realize that.

I remember when New Horizons flew by Pluto, I was telling a friend about how exciting it was, and she said, “Why did they even go to Pluto? It’s not even a planet anymore!” And it impressed upon me the impoverished understanding that many people have about these sorts of missions. A lot of people seem to think a spacecraft is built in a matter of months, and then a rocket launches, and then the spacecraft just gets where it’s going in a few weeks—almost as if NASA had just pulled a spacecraft off the shelf and fired it at Pluto. If all you noticed was the final approach and flyby, it would have seemed like a quick and easy thing, when, in fact, it took more than a decade to get that mission approved and nine years of flight time to reach Pluto. I mean, these are projects that can take entire careers and sometimes entire lifetimes.

There’s obviously a direct connection to Europa, too. The phrase “one inch from Earth,” to me, was evocative not only of the programmatic struggles of interplanetary exploration but also of the notion that complex life might exist just two planets over on this creepy little moon orbiting this weird, giant ball of hydrogen. If life can get started there, that probably means life in the universe isn’t like a single cactus in the desert. It’s more like a blade of grass in a meadow. It’s going to be everywhere. And the idea of this cosmic discovery being so close to Earth really resonated with me, and it resonates within that phrase.

What most surprised you when you started writing this book?

What most surprised me was that I didn’t know anything about the subject! I went into this thing, early on, feeling like I had a solid grip on the field of planetary science, how NASA works, how the scientific process works and the sorts of people who do this kind of work. But it struck me on almost the first day that I was clueless.

I remember the first time, several years ago, that I attended the annual Lunar and Planetary Science Conference near Houston, Tex. I went in ready to get all these amazing stories and learn all these spectacular things. But the science seemed as dense as a neutron star. I didn’t know anything. I almost broke down in tears. It was bad! But it was liberating in a way because as soon as I realized how little I knew, I was able to approach the subject with a total beginner’s mind and with a sense of wonder that I want the reader to experience, too. So I set a rule from the outset, which was that this book would have zero cynicism and irony. And I think I accomplished that goal.

You describe in the book the antagonistic relationship between Mars-focused folks and many others in planetary science, in which the Mars community’s success in lining up missions comes at the expense of other targets for otherworldly exploration. It seems like the power of the Mars contingent is a force that has shaped NASA’s entire planetary science division and really the whole field itself. Is that still the case?

I like to say that Mars is like the Death Star from Star Wars. Because at any given moment, it could destroy plans for any of the planets or moons under consideration for exploration. The Mars community has always been astoundingly good at that on a program level—maintaining a logical, carefully planned series of missions that all progressively lead to answering some high-impact science questions. But they are benefiting from another natural, built-in advantage: NASA is first and foremost a human spaceflight organization, and the agency wants to send astronauts to Mars. Astronauts are never going to land on Europa—not outside of science fiction, anyway. Astronauts are never going to land on Titan, and they’re never going to land on Venus. But they’re going to land on Mars someday. And because of that, there’s an urgency to understand Mars in a way that doesn’t exist for the outer planets.

All things being equal, though, if given the choice, I think NASA as an organization would still prefer to go to Mars—that was certainly true during the darkest days of the efforts to send something to Europa.

What were the darkest days, exactly?

Probably when Mars Sample Return got the highest recommendation for a flagship mission in the last Planetary Science Decadal Survey [a planning effort that provides recommendations to NASA and other government agencies for major science priorities every 10 years]. It’s difficult to overstate how much of a blow that was to the heroes of the book. If not for the intervention of Congress—and particularly John Culberson, who was a Republican representative from Texas—Europa Clipper probably wouldn’t have happened at all. Culberson wanted NASA to go to Europa because he thought finding life there could be a unifying force for the agency— increasing the chances it would regain the sort of funding and spirit it had during the Apollo era. And Culberson made it happen.

David W Brown
David W. Brown. Credit: Romney Caruso

So, with NASA’s Mars fever in mind, are things getting more equitable in planetary exploration in terms of destinations and priorities?

Maybe. The Mars community apparently wants small missions going forward—to study the Martian subsurface and any deposits of water ice, and so on. That creates an opening for other bodies in the solar system to have their moment.

My suspicion is that a sample-cache-return craft is going to fly to Mars regardless of the latest Decadal endorsements. That might be heretical to say aloud, but I think that we’re just too close to achieving this thing that scientists have been seeking since the 1980s. We’re not going to let those sample tubes sit on Mars for another 20 years. Because NASA and Congress seem amenable to getting an outer-planets flagship flying, I think we’ll start seeing dual flagships fly every decade. But I might be entirely wrong about this, and the next 20 years could be the new Dark Ages for interplanetary exploration.

When I first started writing this book, the realm of the outer planets was one of nothing but woe and sorrow. But now I get a sense of optimism that wasn’t there before. A lot of it is because Europa Clipper was eventually approved and because things such as Dragonfly, a plutonium-powered quadcopter planned to launch to Titan in the late 2020s, not only are going to explore another body but are going to do so with panache. When you have these sorts of audacious strides to places that are just incredibly compelling, I think it has kind of a halo effect for the broader community.

I hope you’re right. Let’s talk a bit about where the book ends—or rather the current status of the mission itself because, as you know very well, Europa Clipper has yet to get even one inch from Earth. The SLS rocket that was originally planned to launch it is not flying yet. And Culberson, the Europa program’s champion on Capitol Hill, lost his reelection bid and is no longer in Congress.

I knew, while writing this book, that I would be chasing a moving target. I mean, for example, I would still be writing the book if I had to keep updating the status of the SLS, which, for most of the project’s history, was its notional ride to space. So I chose to end the story in 2015, when Europa Clipper officially became the flagship planetary science mission of the American space program. You don’t need the clichéd final scene with a rocket launch because that’s nothing next to the epic struggle to make the mission real.

The Mission is in many ways a heist story. A group of smart people, each with different talents and connections, came together to achieve a common goal. It’s like Ocean’s Eleven, but instead of robbing a casino in the end, they get a spaceship called Europa Clipper.

In terms of where Europa Clipper is [as of early 2021], they have completed their critical design review and are beginning to build their spacecraft in force. You’ll soon be able to go to the NASA Jet Propulsion Laboratory (JPL) at the California Institute of Technology and see this thing going from PowerPoint to reality—under construction in High Bay 1, a clean room where spacecraft are built.

Already smaller elements are in development. For example, you can see the wiring harness—the actual wiring that’s going to fly to Jupiter—in a clean room at the Applied Physics Laboratory at Johns Hopkins. The mission’s scientific instruments are well into development. There are actual parts and pieces that you can see now for a spaceship that is actually going to fly to what may be the most likely place in the solar system, aside from Earth, to harbor life. And it’s thrilling to see how meticulous the process is—how many little things go into creating this giant thing.

When Europa Clipper is finished, the spacecraft is going to have the wingspan of a basketball court. But right now it’s at a human scale, you know, of people twisting wires and bending metal. And that, to me, is deeply moving. They’re doing some hard engineering right now, too. And as they do this hard engineering, the science is moving on. We’re learning more about how plumes of water might be venting out of Europa’s subsurface seas, where they’re coming from, how the overlying ice behaves.

NASA’s Juno spacecraft, currently at Jupiter, had its mission extended to do flybys of some of the planet’s icy satellites. So we’re going to be getting more data that hopefully help to shape the mission.

So is Europa Clipper out of the woods yet?

I think it would take a major crisis at NASA to actually shut the mission down, so it’s probably going to fly one way or another. So from that point of view, yes, it’s out of the woods. Now, in terms of the hard technical decisions that still need to be made and the financial elements that need to come together in the years ahead to keep the project on track, I’m less sanguine. Will Europa Clipper have enough money to fly, for example, the wide-angle camera? I don’t know. I hope it will, but it has already lost instruments along its long path to the launchpad. So it’s almost certainly going to fly. But what it looks like when it flies is still a little hazy.

In terms of the broader Europa exploration sequence, my Magic 8 Ball is much less optimistic. When John Culberson lost his election, Europa Lander, the follow-on mission in development, lost its greatest political champion and appropriator of funding. Europa Lander is important because Europa Clipper is probably not going to find life. It is studying Europa’s habitability and will help determine where life most likely might exist on the ocean world. It will take a lander to set down on the surface and dig or drill or melt into it, looking for evidence of things that once wiggled.

It’s an extraordinary mission and precisely the sort of “dare mighty things” project for which JPL is famous. More than $100 million has been spent on it, but work has now essentially stopped. If the lander gets an endorsement by the Decadal Survey, I have a feeling that work would resume immediately and that it would launch only a couple of years behind schedule. But that endorsement is a big “if.”

What are you working on now? Might it be another book?

Yeah, a book about an adventurous team of scientists who have been doing pioneering work in Antarctica studying rapid sea-level rise. I’ve already been on one expedition down there with them. It’s not a sequel, of course, but there is a lovely connection to The Mission because some of the world’s foremost experts on Earth’s cryosphere are also interested in Europa. Some people study Antarctica so they can understand Europa. It’s certainly easier to get to, anyway!