IT WASN’T ENOUGH TO MAKE THE STYROFOAM SOLAR system over his bed. The boy needed toothpicks, too, for the moons, and he pressed them into each planet, none for Mercury or Venus, one for Earth, two for Mars. He puzzled over Jupiter, the dozen discovered being too many toothpicks, so he accounted only for the four found by Galileo in 1610. The moons were made of crumpled masking tape, which he skewered and placed into orbit. And while little Europa wasn’t labeled or anything, it was with young Robert Pappalardo even then, on a two-inch wooden spike in a foam world of orange and red.
In 1970 Robert’s dad packed the clan Pappalardo into the family car and steered south to Virginia, one long, continuous drive from Jericho, New York, on the north shore of Long Island, west through the city and then down along the coast. The trip ended on the Chesapeake Bay Bridge-Tunnel, which intersected the “path of totality” of a solar eclipse, the reason for the excursion. A total eclipse. A TOTAL SOLAR ECLIPSE. The sun blocked by the moon but for phantasmal arms of a shimmering corona, a black hole ripped in the daytime sky like some portal to another dimension, day turned to night for minutes and animals going crazy because what the hell is going on up there?—but across only a spaghetti strand of the United States, everywhere not in the path experiencing a miserable and pathetic partial eclipse, the moon taking a bite from the sun but nothing else, the animals not even noticing.
Anyway and either way, he didn’t get that lesson, young Robert, five at the time and not yet of the toothpick moons, the sedan seating only so many, and at some point, Bob—we’re sorry, really, and we’ll make it up to you—we’ve got to make a cut and, Bob, look, you would miss an awful lot of school for this trip and you love staying at your grandparents’ so what do you say? We’ll catch the next one? OK? OK.
Thirty-four years later, he thought of that, the eclipse, the craft store solar system, the masking tape Europa, when they offered him the moon from the ninth floor of NASA headquarters. Europa. It was discreet, but it was an offer. It happened between meetings on October 22, 2004. He was there that day on loan from the University of Colorado, where he was an assistant professor, to advise the agency on JIMO—the Jupiter Icy Moons Orbiter—and what could be achieved from further expeditions to the Jovian worlds. Pappalardo was part of the mission’s science definition team, an ad hoc group of scientists who kneaded the knowns and knowledge gaps of a celestial object or system and determined the scientific objectives that should thus drive a prospective mission there. The simple ability to go somewhere started conversations, but before the National Aeronautics and Space Administration would pay engineers to spark blowtorches and build spaceships, there had to be a reason, some overriding and scientifically compelling purpose beyond Because It’s There.
The Jupiter system was the destination, but Europa was the goal, the target, the quarry. Beneath the frozen moon’s granite-hard ice shell was a liquid saltwater ocean, long hypothesized1 but at last discovered by physicists at the University of California, Los Angeles.2 If life existed anywhere else in the solar system, it was in that water—and not fossilized microbes like they scratched and sniffed for fruitlessly (and relentlessly) on Mars, but conceivably complex life—fish!—and few causes could be more compelling.
Still, no way it would ever fly, JIMO.3 Bob knew that. It was too big, too expensive. Bob had been part of previous Europa mission studies far more feasible, financially and technologically, that died ultimately and unceremoniously in agency filing cabinets. JIMO would have been a thrilling, monumental mission, certainly—would have transformed not only Europan science, but the very nature of planetary exploration itself—but something so big needed the sort of sustained support unlikely to last long, and the probability of a pulled plug was why a manager from Jet Propulsion Laboratory, NASA’s research and development center in Pasadena, California, pulled him aside.4
Bob, began the furtive conversation, I hear that maybe you’re not satisfied teaching.5
WHEN PAPPALARDO WAS a child, astronauts worked and played on the moon. It was just normal, a thing people did, like work in a factory, bank, or bakery. They set up seismometers. They collected rocks. They explored this strange new world and encountered mystifying phenomena: spots of orange dirt on its plaster landscape, jarring flashes of light when they closed their eyes. Scientists on Earth solved these puzzles: the former formed by fire fountains in Luna’s primordial past;6 the latter, cosmic rays colliding with retinas.7 Astronauts drove cars up there. They played golf. They brought mice with them. Pets! In space!
Bob was never going to be an astronaut—that just wasn’t in the cards—but he was a child of Star Trek, and across five-year missions, Spock pointed the way in first run, and then in syndication, and then in animation (the Vulcan really drove the point home): science. During high school, Bob worked at Vanderbilt Planetarium in Centerport, Long Island, not far from his house. A few years later at Cornell University in Ithaca, he found the field of planetary science the way everyone else in the wider discipline did: through a Carl Sagan Moment. Upon enrolling, Bob had intended to take up the ancient art of astronomy, but problem the first: there was no astronomy major proper at Cornell; the field was taught under physics. Problem the second: physics. Bob therefore soon switched studies, his base camp now the university’s new geology building. Myriad mineralogy labs lined its hallways, and to study the stuff of the Earth was to spend long days and late nights in them, over big, binocular-type microscopes adorning tall black lab tables. Pappalardo was seated in one such lab on one such night behind one such microscope when another student, first name John, last name Berner, and so of course they called him Bunsen, walked in.
Hey, Bob, asked Bunsen. You know about this course Sagan is offering? This course on icy moons?8
Bob did not know about this course Sagan was offering, this course on icy moons, but he went home that night, pulled out the course catalog, and looked it up. ICES AND OCEANS IN THE OUTER SOLAR SYSTEM. Instructor: SAGAN, CARL.
That Carl Sagan, yes. He of Cornell, yes, of course. The prominent professor was for Bob part of the university’s initial allure, but Sagan didn’t always teach, had a lot going on. Carl Sagan, recently of Cosmos (book and television series) and The Tonight Show with Johnny Carson (television series). Carl Sagan, of the NASA spacecraft Voyager 1 and 2, the robotic explorers that in 1979 transformed the four telescopic dots of Jupiter’s moons into jaw-dropping globes of fire and ice, and later, around Saturn, revealed worlds diverse, living, geologically active, almost fully-fledged and practically planets (further study needed). Carl Sagan of the spacecraft Viking 1 and 2, which in 1976 revealed the Martian surface to be barren, though certainly in possession of everything necessary for life to exist (further study needed). Carl Sagan, a superstar in a profession bereft even of minor celebrities, who brought astrophysics into blue-collar living rooms, who in turtlenecks and with windswept hair spoke like a philosopher, practically in verse, and presented the pursuit of knowledge as something intrinsic and vital to the soul of every human being. Carl Sagan, who used his platform and lilting baritone to advance social causes, who planned protests against nuclear weapons test sites, arms linked with fellow activists, who crossed police lines and was placed gladly under arrest—Armageddon’s Thoreau—in order to advance the cause. Page one the next day: a rebel astronomer in handcuffs! Carl Sagan, with a Ph.D. behind his name and a childlike imagination inside his head, who had, for example, lobbied for a light to be added to the Viking lander so that at night Martian animals might be attracted to it and scurry up to investigate.9 Well, why not? Nobody knew what waited on the surface of the Red Planet.
That Carl Sagan.
It was a graduate-level course. Bob the undergrad had to request permission, and Carl the professor had to grant it. Bob did. Carl did. The peculiar part of taking a celebrity scientist’s class, Bob soon learned, was that you began to see him as a standard-issue human being. There is Carl Sagan with a coffee stain on his shirt. There is Carl Sagan making a caustic and callous remark about the student operating the slide projector. There is Carl Sagan being boring, writing another excruciating equation on the blackboard. There is Carl Sagan, exemplary but ordinary teacher, whose class, unbeknownst to Bob, would change the trajectory of his (i.e., Bob’s) life. It was in that classroom—conventional inventory: desks, blackboard, snapped chalk, and tile flooring—that Bob first learned about the most mesmerizing moon revealed by the two spacecraft Voyager: the world Europa, this icy-blue eyeball circling Jupiter, etched mysteriously with crazy brown scratches. Some speculated that an ocean might exist beneath all that ice—the physics suggested it—but, again, more study was needed.
Bob completed his bachelor of arts at Cornell and pursued a graduate degree at Arizona State University. He hit a wall there, however, and left before completing his master’s in geology. The 105-degree summers didn’t help, the Tempe sun so severe, so low in the sky that you could almost reach your arm into it—how he hated Arizona, and the conservatism of the place, and the corrupt governor Evan Mecham, who was just thoroughly reprehensible: canceling the state’s paid Martin Luther King Jr. Day holiday, defending the use of racial slurs. (Bob had even worked on the Mecham recall, though the governor was impeached for, and convicted of, obstruction of justice and misusing government funds, and removed from office before voters could do it themselves.) Bob had friends in the simmering state, of course, followed local bands and played guitar at open mic nights and sang Dylan and the Dead, but graduate school was just dispiriting, basically hopeless, and with little promise of hope ahead. He realized a little too late in his program that his master’s thesis was overly aggressive in scope and that he would never be able to finish it. His graduate advisor, recognizing a lost cause, seemed to have moved on. So when Bob learned from a friend about a one-year internship at Vanderbilt Planetarium, where he had worked in high school, he applied and was hired. A one-year sabbatical from school—that was the plan—it would be a kind of collegiate convalescence—but maybe he was just finished with the enterprise entirely and would never return.
He liked life at the planetarium, stepped right back into it, and he was teaching the stars to students who were captivated, eager to learn, and Bob talked daily in the dark to the backs of two hundred heads, and it was rewarding, worthwhile work. That master’s had just stretched on and on and on, and he looked at what he was doing now, and maybe he didn’t need graduate school after all.
The internship paid ten thousand dollars, which stretched just enough to cover rent for a moldy basement apartment on Jackson Avenue, a little dead-end street in Huntington, and not far from his new job. He shared said quarters with a Vietnam vet who would sometimes have his homeless friends over to sleep on the floor. The substandard accommodations were worth it because Bob enjoyed what he was doing, and the joy increased with each passing week and month. Only twelve of those months were funded, however, and after enough pages from the calendar fell to the floor, a grim reality set in: Bob was running out of time.
Then one day, while he was practicing at the planetarium dome console for the next show, the phone rang. He answered.
Bob, said the voice, how would you like to come back?10
It was Ron Greeley, his graduate advisor and mentor at ASU.
Before that call, Bob had felt that maybe Ron had given up on him. It’s part of what made the planetarium job such a relief: that lack of disappointment looming gloomily from above. Ron was a professional, a professor’s professor, a founding father of the field of planetary science, and was above all a soft-spoken gentleman. But you felt his disapproval. The call was evidence that maybe Ron still believed, still saw potential in wayward Bob. It was just so nice. Bob’s thing, his gift, his curse at the time, was that he saw details—so many details—and his mind adamantly insisted on assembling those details into a big picture, a coherent story. Ron picked up on this, said a master’s thesis was just too small to contain what Bob had been doing. And Ron was right. It should have been easy, and yet it was taking years. So the student and the professor had the conversation, and not long after, Bob went back to Arizona, which was still an awful place, and the two of them turned his master’s thesis into a doctoral dissertation. Dr. Pappalardo crossed the stage in 1994.
After a lengthy postdoctoral research position, Bob found a job as an assistant professor of planetary science in Boulder, Colorado, in 2001. The singular focus of his professional life had been the evolution and activities of “icy moons”—the frozen satellites circling Saturn and Jupiter and Uranus and Neptune, those planets so large as to host planetary systems of their own, in miniature. That’s what he studied, that’s what he taught.
But was he satisfied teaching? he was asked that day on the ninth floor of NASA headquarters.
He was, but maybe he wasn’t. He was a good instructor, he thought. He liked the university and he loved living in Lyons, just north of Boulder, along the foothills, and lying in his hammock on the front porch, watching the sun sink behind Longs Peak—what climbers called the “flat-topped monarch” of Rocky Mountain National Park.11 He had a girlfriend. He had a cat. He contra danced—Boulder was great for that because you could drive north to Fort Collins or south to Denver, both with thriving communities of light-footed locals—hands four from the top, gents on the left, ladies on the right, face your partner, do-si-do—and every weekend, he’d strap on his Volkswagen Passat, this silver thing, custom plates (ICY SATS)—a little too much car, he thought, but he had the cold weather package and it was fine, and he had snow tires—and he’d drive north or south to swing his partner round and round.
So he was content, but was that enough? Was that the same as satisfaction? Colleagues joked that Pappalardo was unhappy in front of the classroom because he took teaching too seriously. Being a good teacher was wearying work, especially at a big state school. You grade two hundred twenty papers, and they are brimming with pages of pilfered prose, and there are only so many times you can debate with undergrads the answer to a multiple-choice question before you start fantasizing about gasoline, matches, and applying both to oneself. His graduate students were great, though—curious, creative, conscientious—and he took care to advise and mentor them as Ron Greeley had advised and mentored him, to sustain that unbroken chain reaching back to Plato’s Academy. Bob relished pairing, like Gregor Mendel in his garden of pea plants, the expertise of different grad students—his potential planetary scientists—to see what might grow from the couplings.12
Bob came to Colorado by way of Brown University in Providence, Rhode Island, where he’d put in six years as a postdoctoral researcher—years longer than most for that kind of position, but he was at the time analyzing data returned from the flagship Galileo, NASA’s spacecraft at Jupiter. He was officially an “affiliate member of the solid-state imaging team,” and who would be in a hurry to leave that? Every two months, Galileo would complete an orbit of Jupiter. The relentless machine made by human hands carried cameras, sensors, and mapping tools, and every second it spent circling Jove served some purpose. When it wasn’t directing data to Earth, Galileo was studying Jupiter below or one of the two dozen natural satellites encountered along the way. (The known number of moons had grown since Bob pressed toothpicks into his painted polystyrene planets.)
Pappalardo’s job was to plan the mission’s “imaging campaigns”: what the onboard camera would take pictures of, and when, and why. That imaging campaigns were even possible was a triumph. NASA made space exploration look easy, but it never was. In Galileo’s case, scientists learned soon after launch that the spacecraft had a faulty high-gain antenna. Its collected data should have surged back to Earth, an Amazon River of zeroes and ones. Instead, it trickled home as though through a kinked garden hose. Galileo, consequently, could return only a fraction of the intended science. For members of the mission, then, it meant being methodical and selective. It wasn’t enough to know what you didn’t know; you had to know the best things no one knew, or even thought to ask, and then have the spacecraft collect the data to answer them. Observation planning was high-stakes work, made more so by the harsh reality of orbital mechanics. You miss your one shot at a particular moon, and that might be it, ever, for an entire generation of scientists. Galileo might never pass that moon in that configuration again, and it might be thirty years before NASA got another spacecraft to the Jovian system to fill the gap.
Galileo’s project and camera leads, in addition to running a spacecraft, taught and managed university departments and advised NASA and generally pushed planetary science forward. Scholars such as Greeley and his counterpart at Brown, Jim Head, or Torrence Johnson, the Galileo science lead, didn’t have time to plan which of the two blobs spotted on Europa might be more valuable to image, or how to image them, or which color filter to use, or what camera mode should be used, or what compression level should be applied thereto. But postdocs and graduate students did have that kind of time, and though Bob was relatively young, his work, and that of his fellow affiliate members of the solid-state imaging team (and the grad students thereon), were critical to mission success. It was tiring, tedious, taxing work. You had to stay on top of it. I mean, the spacecraft never stopped. The advisors consistently and unflinchingly reviewed the plans. Greeley in Arizona would sometimes ask of Bob or Louise Prockter, a graduate student at Brown, Is that picture worth a million dollars? Because this costs a million dollars per picture.13 And you had to make the argument that it was, or you had to find something better to target, and it was back to zero. And you learned to argue the science. On this flyby, do we take images of Europa, or do we point the camera instead at Gilgamesh Basin on its fellow traveler Ganymede, Jupiter’s largest moon? The Europa images would be the highest resolution ever taken. The Ganymede images would be among the worst. But those few feeble Ganymede grabs might settle some surface-age question that has long vexed scientists. Which do you choose? (They chose Ganymede.)
By the time Bob took the job in Boulder, if he wasn’t yet the world’s foremost expert on Jupiter’s moons, and Europa and Ganymede in particular, even the world’s foremost expert might think he was. He had managed, over the course of his college career and afterward, to read everything ever written about the Jovian worlds, and he possessed an unnerving ability to retain not only the literature but also the location of said literature—e.g., “I recall reading a paper on that in Nature in 1979. Turn three pages in and you’ll find a chart that might be useful.” He had a fine run of accepted papers on the geophysics of Galilean satellites and spent an awful lot of time writing reports summarizing where, exactly, scientists were in their thinking about the icy worlds. For planetary scientist Fran Bagenal’s book Jupiter: The Planets, Satellites and Magnetosphere (literally “the book on Jupiter,” as in “She wrote the . . .”), he led the Ganymede chapter and cowrote a good bit of the Europa chapter as well.
When Bob first came into the field, all the foremost experts taught—Greeley, Sagan, Head—and he had benefitted immeasurably. Who was he to do less than the founders of the field? But by 2004, it felt like all the best young scientists were moving to research institutions. How would that affect planetary science? Who would teach the basics to the next generation? Could Bob? Would he really be the best person to carry the torch if he became a burnt-out ice moon obsessive arguing with undergrads the merits of “D. All of the Above” every March during midterms?
Being pulled aside and presented with this overture from Jet Propulsion Laboratory—it was exhilarating. The lab, located in the San Gabriel Mountains of Pasadena, was an important place when it came to altitudes above the thermosphere. As an institution, it had long secured a future for the city, which was first given geography in 1771 as part of the Mission San Gabriel Arcángel’s planting of Catholic flags across the lower territories.14 (The Spanish Franciscans didn’t really count the indigenous peoples’ millennia of settlement and cultivation of the land. No, it definitely all started in 1771.) Next came colonists from the northeastern United States,15 and by 1886 Pasadena had become something of a winter outpost for well-heeled New Englanders. The Second World War made Pasadena permanent when Southern California served as a staging area for the Pacific campaign. While the army was in town, it partnered with the California Institute of Technology, whose engineers were developing an American response to an ascendant German technology called jet-assisted takeoff rockets. Thus was born Jet Propulsion Laboratory. Still managed by Caltech, it was, since 1958, more famously a NASA center, having evolved into the primary robotic research and development arm of the agency. (The buildings belonged to NASA; the employees belonged to the university.) All the multibillion-dollar large strategic science missions—the flagships—flown beyond the asteroid belt had been designed, built, and flown from there: Voyagers 1 and 2, both still coursing through uncharted regions of space; Galileo, now vaporized in the Jovian interior, its mission completed; and Cassini, only four months now in orbit around Saturn. Of course, JIMO, too, was a lab effort, and evidence that not everything its engineers touched launched.
JIMO was part of Project Prometheus, a NASA headquarters-directed initiative to use nuclear reactors to power the propulsion and payload of spacefaring vessels. The program was a personal priority of Sean O’Keefe, the administrator of NASA, and was modeled in part after the U.S. Navy’s fleet of nuclear submarines.16 (O’Keefe was a former secretary of the navy.) The idea was to send spacecraft on long-term, multiplanetary science missions in the farthest, least hospitable reaches of the deep outer solar system. JIMO would be its pathfinder, its ship of the line, its fission-fueled flagship—the first of what could be an armada of similar such vessels searching the cosmos. The Prometheus reactor would change everything. Power was king in space exploration. No matter what went wrong millions of miles from Earth, the mountain people of JPL could summon an ancestral sort of strident braininess, whiten blackboards with complex equations, and send signals clear across space bearing So Crazy It Might Work instructions to get a wayward spacecraft back on track. They could heat the spacecraft by boosting power to certain components or orient it to endure direct rays from an unfiltered sun. They could shake the spacecraft, spin it wildly, extend arms and swing them round and round. They could reprogram every byte of its onboard computer. But in order to do any of this, the spacecraft absolutely needed to maintain power. If the lights went out, it was Kobayashi Maru. It didn’t even take a lot of power to keep things running. The New Horizons spacecraft set to launch to planet Pluto in 2006, a mere two years away, would travel three billion miles—to the very edge of the sun’s influence—and run rigorous analyses on the unmapped world using two lightbulbs’ worth of power: about two hundred watts.17
The Prometheus reactor, however, would produce up to two hundred thousand watts of power—a number so large that scientists had no context at all for how to use it.18 If power was king, Prometheus would be the supreme and undisputed overlord of the solar system. So with the administrator’s blessing, JPL engineers swung for the fences with JIMO. They settled on a spaceship that was as heavy as an eighteen-wheeler and longer than the Millennium Falcon. It would require three separate launches to get to space and would need to be assembled in orbit, the same way NASA was building the International Space Station. It would then fly to the Jovian system, enter orbit around one of Jupiter’s moons, look around, study this area or that, fly to another moon, orbit it, and another, and another.
JIMO was ideally suited for studying Europa because the moon resided in the heart of the Jovian radiation belt: a pulsing, rippling, four-million-mile halo of death that surrounded the largest planet in the solar system. Electrons there zipped about at just under lightspeed, and when those particles smashed into a lesser robot’s brains, zeroes got flipped to ones, and the spacecraft might have a very bad day indeed. Maybe a vital image would be wiped from existence. Maybe the computer instruction that said Absolutely do not do this suddenly read Go for it buddy—YOLO! and the billion-dollar mission would be lost forever. A starship like JIMO, though, was no mere robot. It was Optimus Prime! It was an electronic Aeneas on a celestial battlefield, radiation but a refreshing breeze tousling its hair. You want a flagship? asked JPL engineers. We’ll give you a flagship.
But first you had to get that reactor into space.
It was the size of a trash can. Something so small couldn’t cause a nuclear accident on the scale of Three Mile Island, or much damage at all, really, even if NASA put its scientists on that problem called “the Earth” and how best to make it go away. If Prometheus blew up on launch, someone might be killed from a chunk of metal hitting his or her head, but there would be no mushroom cloud, no documentaries thirty years later about where all the cows with two heads came from. But for some people, crowning a colossal missile with a uranium-powered, atom-splitting nuclear device and firing it into orbit . . . it was just a little too . . . doomsday? An awkward brush against the concept of an intercontinental ballistic missile? The thing wouldn’t switch on until it was six hundred miles from Earth, but flying fissile fuel over Florida retirees . . . it was asking a lot.
The real killer, though, was JIMO’s price tag: ten billion dollars.19 No science mission had ever cost that much. The Hubble Space Telescope cost a third of that.20 The shuttle Endeavour—the shuttle fleet then being the heart of human space exploration (NASA’s raison d’être)—cost a quarter of that.21 JIMO may as well have come in at a hundred trillion dollars. Ten billion? NASA headquarters would never keep that kind of cash flowing for a science mission. Everyone knew that JIMO would die the moment the NASA administrator retired—and all signs suggested that Sean O’Keefe, who pushed Prometheus prominently, would do just that very soon. But JPL wanted that money, so JPL needed a plan.
Enter Bob Pappalardo. It was regulation DC weather for late October that day: cool and overcast, with a light breeze.22 Over lunch at NASA headquarters, only a few minutes’ walk from the Smithsonian National Air and Space Museum, a manager from California explained to the assistant professor from Colorado that while Jet Propulsion Laboratory had the best spacecraft engineers in the world, project teams needed strong scientists on point. After all, engineers left to imagine what’s possible without scientific guidance can come up with ideas that are . . . unorthodox? Unconstrained by reality? We can’t keep up with Europa science the way you can, Bob, and JIMO isn’t the only thing the lab has in the hopper for spacecraft concepts to get there. You’ve got to be ready. If Congress sends an extra billion dollars to NASA, the agency is going to ask for ideas. Let’s go to Venus or Pluto or Neptune’s moons, and you need something to slap onto the administrator’s desk. Glad you asked! We’ve been thinking about this one for a while! We’re all one big, happy space program, but it’s every NASA affiliate for herself. If Jet Propulsion Laboratory isn’t ready with the razzle-dazzle, Goddard Space Flight Center in Greenbelt, Maryland, or its neighbor, the Applied Physics Laboratory in Laurel, might get the gig, and then you’ve got a thousand Pasadena engineers on the payroll with nothing to design, build, or fly. And this we know: Once JIMO joins the choir invisible—it’s a dead mission walking, Bob—NASA is going to try Europa again. They’ll ask for a more manageable mission concept. And they want density, not volume. NASA headquarters knows science from science fiction.
Bob knew that a big part of the lab’s Europa program was science fiction—and not just JIMO. By 2004, JPL had spent money on such Europa concepts as “melt probes,” which would have required landing on an unmapped moon in a robot-broiling radiation environment and penetrating an ice shell harder than concrete and kilometers thicker than any hole ever drilled on Earth to reach an ocean that, technically, might not even exist.23 Good luck with that.
Even superb studies of plausible mission concepts had been unable to find traction at headquarters, as Bob knew firsthand. He had consulted briefly on a JPL study in 1998 for a possible spacecraft called Europa Orbiter—an outgrowth of an ambitious program called Ice and Fire—and it was a real contender. The project gathered momentum when the spacecraft Galileo got a good look at Europa’s tarnished crystal facade, and magnetometer measurements hinted at liquid water churning beneath its icy exterior. NASA convened a science definition team to establish the best science attainable with a small, sub-billion-dollar spacecraft. They determined that Europa Orbiter’s goal would be to answer the water question: Was it real? Or something else? Then, if it was real, the orbiter would map the ocean in three dimensions and, lastly, figure out why Europa’s surface looked like a cue ball scraped by a madman with a rusty nail.24 You do those three things, and you’re in good shape for a subsequent lander mission, a concept for which was already on the books. It was about the size of a pizza, the lander, but it would reveal an awful lot about the Jovian moon’s surface—e.g., was it solid or slushy?
Based on Jet Propulsion Laboratory’s promise of an inexpensive Europa mission able to overcome the historically ten-figure toll to cross the asteroid belt, in 1999 headquarters signed on and seeded the lab with fifty-eight million dollars to begin detailed development work.25 And once that money was spent, lab leaders came back to headquarters, all smiles and with a plan in hand that was twice the quoted cost—but, hey, you’re on board, right? And, hey, headquarters definitely was not, and Ed Weiler, the head of science missions for NASA, canceled it with prejudice.26
THIRTEEN POINT EIGHT billion years earlier—three minutes, in fact, after the universe began—hydrogen nuclei formed: good old atomic no. 1, the lightest element on the periodic table.27 Until then, space itself had been bounding outward from a single point to the entire observable universe. It cooled into a quark soup, quarks came together to form baryons, and electrons were new in town and turning heads.28 It was a busy three minutes. When hydrogen nuclei stepped onto the stage (though not into the spotlight—light as we see it didn’t exist yet),29 so too did those of helium, lithium, and beryllium (nos. 2, 3, and 4, respectively, though their parts were small indeed), and it took another four hundred thousand years of universal cooling before the nuclei could draw in those eligible electrons and form stable, bona fide atoms. Over time those atoms met, became gravitationally attracted to one another, and formed clouds in space called nebulae. A trillion galaxies or more formed from the clouds over the next nine billion years, and one of them was spiral-shaped and destined to be called the Milky Way.
Our nebula was not a particularly peaceful place, though it was stunning, from the outside far away and looking in: a celestial cloud of white, blue, beige, and burgundy, and it was very, very big—quadrillions of miles from end to end—just ridiculously large, really. All across the nebula, stars formed and exploded with unnerving regularity, contaminating the cloud with smithereens of stardust from which other stars and systems would emerge and expire and further enrich the ether.
It is how the elements beyond beryllium were born. A small star is a fusion-powered factory, its dense and powerful interior slowly squeezing together the nuclei of hydrogen atoms and turning out fresh helium. Fusion reactions let there be light. Larger stars do this on a scale commensurate with their size, and when their available hydrogen is used up, fused fully into helium, they double down on the whole process and start fusing helium to beryllium and carbon, and down the line to iron—our friend Fe, twenty-six protons now forced into a single atomic nucleus. And that’s as far as a star gets before all that iron and heat and pressure destabilize it, and it finally says forget it and explodes in a cosmic cataclysm. The resultant forces then really get to work on the atoms at hand, chaotically fusing and forming everything up to (and including) uranium, with ninety-two protons stuffed in its nucleus: our atomic bombs, fueled by supernovae themselves. And by now, the bulk of the periodic table is forged and scattered across the cloud, again and again and again, stars forming and failing and feeding the fertile miasma.
Across ages, epochs, and eras, meanwhile, a paltry puff in the cloud that would become our own oozed fluidly and with a sonorous turbulence. From its nascency, gravity really worked on our little parcel of nebula, drawing it ever inward on itself, slowly but inexorably, until at last, nearly five billion years ago, it buckled and collapsed. As it did, its erstwhile inner turbulence, those fluid motions, caused our contracting cloud to exhibit a net sense of rotation. Our tiny wisp began to spin. The more material it drew in, the faster it spun, and though the sun today could hold more than one million Earths, it began like this, as a swelling union of dust and hydrogen, and it grew and grew and grew, its rapacious core inhaling everything available, growing ever denser, more massive and molten, one mote of dust at a time until nearly all of the cloud was consumed. It was becoming a protostar.
The spared, swirling fraction of a fraction of gas and dust on the protostar’s fringes flattened all the while into a thin disc of vast diameter, the way pizza dough stretches and flattens as it is tossed. These particles, they aspired to such sizes as grains of sand, and perhaps one day grains of rice, but for now, they were but specks circling some crazy ball bursting from within. Over time they clustered by chance into particle pelotons behind which other specks could hide, drag diminished, energy saved, the groups growing bigger and bigger still. The clusters’ comfortable wakes tempted more things yet, and in due course these growing balls of material reached sizes sufficient to start self-gravitating and attracting yet more stuff, until they themselves collapsed into solid celestial objects: the first asteroids. Onward they went, colliding with one another and growing larger and larger as they accumulated debris and other solid material. The farther from the swirl’s center you were, the lower the temperature, and thus the more solids these planetesimals had handy, because a new building block was introduced to the material available: ice. This swarming supplementary matter allowed planetesimals to grow ten times larger than Earth, itself now forming from rock and metal nearer to the disc’s interior. Planetesimals soon showed signs of becoming protoplanets with attendant superhot centers and such distinct, differentiated layers as crust, mantle, and core. All of this was happening at once: the protoplanetary disc, the protostar, and the whole thing still submerged in the thinning local nebula.
Then, the awakening. The heat and pressure at the disc’s core, ever increasing and increasing, could increase no more in its present state, until fantastically, this enormous, round, burning-hot thing—almost the entire mass of what was once merely a haze of atoms—reached eighteen million degrees Fahrenheit, and its pressure and heat were now so great that the nuclei of its constituent hydrogen atoms commenced fusing together, creating helium and releasing astounding amounts of energy. As the newborn star flickered to life, it blasted a wave of heat and plasma outward, concentrating the cloud at the orbits of the protoplanets Jupiter, Saturn, Uranus, and Neptune, each of which immediately went to work acquiring this sudden influx of hydrogen and helium. Jupiter, the hungriest of the four, was largest and best positioned to dominate, and within a million years, its atmosphere was as massive as its core: ten Earth masses of solid stuff surrounded by ten Earth masses of hydrogen and helium. Feeling now like a real master of the universe, it then dove headlong into an unstable, runaway phase of accretion, and in ten thousand years—on cosmic timescales, the firing of a brain’s neuron—Jupiter inhaled three hundred Earth masses’ worth of gas.
When a planet forms that fast and that heedlessly, weird things happen around and inside it. Jupiter migrated, first inward, truncating the disc of debris available to the protoplanets nearer to the sun, leaving Mars material enough only to grow twice the size of Earth’s newborn moon. Saturn saved the solar system by pulling Jupiter again outward and away from the sun. The planetesimals now settled into place between Mars and Jupiter, and were so agitated by events and the giant world’s gravity that they were unable to organize into proper planets. Thus was born the asteroid belt.
At the severe pressures of Jupiter’s interior, hydrogen acts like a metal. Hydrogen is simple: it’s basically just a proton with an electron going around it. Take a ball of hydrogen atoms and squeeze it tightly enough—say, a million times the pressure of Earth’s atmosphere—and the atoms get so uncomfortably close to one another that the electrons stop caring which protons they’re orbiting. As long as there’s a proton nearby—any proton at all—the electrons are happy, and they will just start hopping around from atom to atom. The interior has, at this point, become a highly conductive metal fluid: liquid metallic hydrogen. The planet’s core heats the liquid metallic hydrogen, causing it to rise, and once it reaches the outer layer, it cools and sinks, again and again and endlessly, generating in the process a massive magnetic field.
In Earth’s night sky, Jupiter is not all that special: a flickerless pinhole of light in a dome of darkness. If its magnetic field were visible, however, it would be the size of three full moons in our sky.30 When charged particles in space travel through that massive magnetic field, they get trapped and start zipping around at the speed of light. Space is a deep, dark, deadly domain, infinite in its dangers, but it is a boundless Switzerland compared with the wilderness of this, the Jovian radiation belt.
As for the rest of the solar system, what nebular material was not consumed by Jupiter, Saturn, Uranus, and Neptune was at last blown away by the stellar winds. It took five hundred million years for all of this to happen, from collapsed cloud to solar system, planets circling and a star to steer them by.
After four and a half billion years, the solar system more or less settled, with a thin layer of life having taken hold on Earth. There, an artist named Giusto Sustermans painted what would become the definitive portrait of physicist-philosopher Galileo Galilei.31 The somber, sober subject was seventy by then, round, wrinkled, bearded lavishly, and posed touching a telescope. Draped in black, a white collar wraps around his neck, and higher up, silver brows furrow below a hairline struggling valiantly to hold on a little longer. The man in the painting seems wise, but more than anything else, he just looks tired.
But when Galileo discovered what he called the “stars of the Medici” orbiting Jupiter, he was preening, dynamic, forty-six, and famous. Already, he was a caustic seventeenth-century version of Carl Sagan. He wrote poetry. He loved wine and women. He sold science to the masses (his books were published in Italian rather than Latin), and in salons from Pisa to Padua, he took his ideas on tour, throwing down against fellow philosophers.32 A graceful winner he was not (and win he did; he was Galileo, after all). He seemed to find a satisfaction only in the scholarly equivalent of Mortal Kombat finishing moves, extracting twitching spines and still-beating hearts from his debate opponents.
Galileo certainly had the CV for such high self-regard. At twenty, he had discovered the law of the pendulum: that the period of its swing is independent of its amplitude. (This had real ramifications for timekeeping, though he would be dead before they could be leveraged.) At twenty-five, he took a swing at Aristotle, asserting that two objects dropped from a great height would land simultaneously regardless of weight; density, he declared, was the deciding factor. He was right and, naturally, was not modest about it.
Cosimo II de’ Medici, the grand duke of Tuscany, eventually made Galileo court mathematician. (Only the pope would have been a better or more powerful patron, and Galileo was friends with him, too.) In 1610 the acerbic Italian fixed a modified spyglass on planet Jupiter and discovered three tiny stars in its vicinity. Observations over several evenings found a fourth, and movement, and it didn’t take long for Galileo to work out what he was looking at: objects in space circling another object. There was no end of implications to this, and no better scientist to make the discovery. Heliocentrism had been around for a while—the Greek astronomer Aristarchus of Samos advanced the idea in the third century BC, though his work was lost in the centuries to follow.33 More recently, just before his death in 1543, the Polish astronomer Nicolaus Copernicus had published On the Revolutions of the Heavenly Spheres, positing that there might be multiple centers of motion in the universe: that the planets circle the sun, and the moon orbits Earth. Absent proof, however, everyone went right on thinking that Earth was center of all things because it was safer, made more sense, and had zero incompatibilities with Scripture and its armed enforcers. Galileo had no such qualms, however, and beat his drum—hard—upending cosmology itself and humanity’s Very Special Place Indeed in the universe. He probably thought a lot about that while spending his last days under house arrest, having annoyed the Inquisition with this heliocentrism business.
The four stars he found were, in fact, moons—Io, Europa, Ganymede, and Callisto, now collectively called the Galilean moons. (They are named for the lovers of Zeus, king of the gods on Mount Olympus, though Galileo did not name them. A German astronomer named Simon Marius did the christening, having had the misfortune of discovering the moons one day after Galileo.)34 So dominant was Jupiter in the whirling, collapsed cloud of cosmic dust and gas that formed the solar system, that it attracted a disc of its very own called the Jovian subnebula. It was a microcosm of the wider solar system, with Jupiter playing the role of the sun and its moons the planets.35 The stuff closest to Jupiter formed a world of rock and metal—Io—and moving outward, as temperatures dropped, ice increased as a formative factor. Europa is made of a lot of rock and some ice. Farther out, Ganymede is icier still, and Callisto—the most distant of the lot—is the iciest of them all.
Europa is the smallest of the quartet. It is a little smaller than Earth’s moon, with a little less gravity. “Small” in celestial objects is relative; one standing on Europa’s surface would notice no curvature on its horizon. Its atmospheric pressure is about one-trillionth that of Earth, meaning, in effect, that to stand on Europa is to stand in space. Above, two major moons hang in the darkness: Ganymede, giant, its pale-bronze hammered surface sometimes smooth, sometimes sharp, scratched, and scaly, splotches of snow seemingly splattered at random; and Io, an unsettling, Gigeresque orb, yellow with stains of orange and brass. Farther out, Callisto, brown and speckled like amphibian skin. There are more than a hundred other moons that could be witnessed on the dome above if you brought a good pair of binoculars, but nothing unsettles the soul like Jupiter, twenty-four times larger than a full moon in Earth’s sky, this looming leviathan, this aptly named and veritable god of planets, robed in bands of tans and reds—a spherical windstorm in space—its clouds of hydrogen and helium ever a slow churn driven by some unknown force from deep within its interior.
Looking down and to the horizon, an astronaut on Europa is casting her eyes across a postapocalyptic Antarctica: an endless tundra of gashed ice. In places, it is snowman white—the stuff of pure water. Elsewhere, it is sepia, seared and poisoned by the radiation belt into which Europa is submerged. Those gashes: in shadows they are cinnamon, scarlet, sienna, and they break up the landscape as though the whole world had been smashed on a marble floor and then reassembled haphazardly. There are steep cliffs and deep troughs and Grand Canyons of ice the color of prison cells. In places, the lacerations curl and meander like spaghetti. Some icebergs tower, some stoop in subjugation, and they meet chaotically across the expanse. It is three hundred degrees below zero Fahrenheit, and there is no weather, no wind, no rain, but there is ferocious radiation: Io-borne ions beating endlessly into the ice for billions of years, making some of its surface something almost like snow, depths unknown.36
Beneath the ice, the ocean, the seafloor, is Europa’s thousand-mile-diameter core, which is made of iron. (Just like Earth’s.) The mantle surrounding it is four hundred miles thick and made of silicate rock. (Just like Earth’s.) A sixty-mile layer of liquid water covers the mantle—not some green alien goo that technically fits some Poindexter’s definition of “water,” or water with an asterisk, or water for extremely large values of x, but liquid water. A saltwater ocean. And the whole world is wrapped in an ice shell fifteen miles or so thick. (Unlike Earth.)
Here is why there is a liquid saltwater ocean on a small moon so far from the sun that its surface is three hundred below zero: 1. gravity, 2. mighty Jove, and 3. the odd interplay of cohort moons. In the time it takes Ganymede to make a single lap around Jupiter, Europa has circled it twice, and Io four times. As they orbit, they pull each other toward and away from Jupiter. Because of the clean numbers—4:2:1—their “orbital resonances” are stable. They’ll go right on doing this forever. (Were they unstable, the forces at play would eventually rip the moons apart. This happened once at Saturn, and its breathtaking rings are a cemetery made of the moons’ mortal remains.) An effect of these contra dancing orbs is that their orbits are not perfectly circular. Sometimes they are nearer Jupiter in an orbit; sometimes they are farther away. When a moon is close to Jupiter, the giant planet’s astounding gravity, in effect, stretches it. When a moon is farther out, it gets respite. Closer, clenching. Farther, solace. It is like squeezing a tennis ball repeatedly. The more you do it, the warmer the ball gets.
If ever Io were an icy world, those days have long passed. No ice could survive the forces so near Jupiter, the heat, the insistent choking by a planet so immense. Io is the most violent body in the solar system; at any one time, there are more than a hundred volcanoes actively expelling hot rock into space. Under the force of Jupiter’s gravity, Io is literally turning itself inside out. Here on Earth, the moon we see today is the same one the cavemen saw, and the dinosaurs before them. Things just haven’t changed that much for eons. But in fifty years, the surface of Io—a moon just slightly larger than our own—will look totally different.
Europa has just enough space from Jupiter that it’s able to hold on to its ice, but not enough distance to be unaffected by the situation in which it finds itself. Those cracks on Europa’s surface are crushed ice under Jove’s flexing fist. It heaves, this body!—the Europan tides rising and falling by a hundred feet or more over its three-and-a-half day revolution of Jupiter.37 The friction caused by Europa’s eccentric orbit becomes heat welling up from the constricted mantle, and though Europa’s surface is six times colder than Antarctica in winter, twelve miles down, the ice becomes water in a flowing, relatively warm ocean.38 And there is a lot of water in that warm, swirling, gushing, meandering, swelling sea: three times as much as there is on Earth, with global currents more powerful than Earth’s as well.39
To create life as we know it, a world needs organic molecules—compounds with carbon, hydrogen, nitrogen, and oxygen, which most planets have. Such life requires water for processes such as ingestion, metabolism, and excretion, and while water is less common than organics, it is certainly found beyond the third planet. Life lastly craves chemical energy, which is the toughest of the three to come by. There is no sunlight in the Europan ocean, and thus no photosynthesis. It’s ink black down there. But on the ocean floor, water touches rock, which is conducive to interesting chemistry. And what Europa lacks in sunlight, it makes up for with unbridled chemical reactions powered by something else. Though its seafloor is a wondrous mystery, all the same, planetary scientists have a pretty good hypothesis for what it looks like: it looks like Io.40
It’s not quite as dramatic down there—Io is Mordor, and Europa’s distance helps stave off Sauron’s more malevolent designs. But the terrible forces causing Io to hemorrhage its entrails are at work on Europa as well, and, on its ocean floor, great geysers gush heat and chemical compounds from the mantle and into the water. This happens on Earth, too, but for different reasons: at the bottom of our ocean, hydrothermal vents ceaselessly billow brutal columns of scorching water, an endless supply of nutrients blasting from the bowels of Earth, and life teems there—life simple and complex—despite the total absence of sunlight.
Ganymede, meanwhile—the third of the three moons swinging about—is an icy world being squished by Jupiter. But because its shell is so thick, it manages to melt only in the middle, leaving its water sandwiched between ice layers. Its water is never afforded the chance to touch rock, which is a bad thing indeed if you want the kind of chemistry that likely yields fish.
No one knows how you go from lifeless material to living material. It is the eternal mystery: Where did I come from? What scientists do know is that it takes a long time to happen. A celestial object can have all the right ingredients—organic material, water, chemical energy—but if the pie hasn’t had time to set, it doesn’t have life on it. The best guess for life’s baking time in the oven: five hundred million years.
Europa’s ocean has had more than four billion years for life to get started.
The possibility of a Jovian moon growing things that swim hasn’t escaped the notice of artists since Sustermans. Author Arthur C. Clarke and film director Stanley Kubrick developed the plot and themes of a story involving the Jovian system based loosely on a much older story by a poet named Homer. In 1964 Clarke went off and wrote his novel, 2001: A Space Odyssey, while Kubrick drafted a screenplay of the same name, and along the way, the two compared notes on each other’s works, incorporating the best stuff into each. The film premiered in 1968, two months before the book hit shelves, and though Clarke had written a masterpiece, Kubrick had created something superlative: a piece of artwork from which there was no turning back.
The pacing and storytelling of the two works track similarly. A magnetic anomaly pulsing from the lunar interior leads astronauts to drill a core sample of the area in order to work out what is happening there. Twenty feet down, when the drill is stopped cold by something unexpected and impenetrable, they begin to dig and soon call in a team with serious hardware to do a proper excavation.
They discover not far beneath the lunar surface a large slab—a monolith of perfect dimensions, 1:4:9—the squares of the first three integers: 12:22:32. When the monolith is exposed—a sign that life on the planet below has reached some level of ability and sophistication—its first encounter with sunrise causes a piercing beam of radio energy to be blasted across the solar system. The plot of each work, novel and film, involves a human expedition to the target of said radio beam.
Here, however, the stories diverge. In the novel, the signal is aimed at a moon in the Saturnian system. To the extent that the spaceship of exploration, Discovery One, flies to Jupiter at all, it is only briefly—a single chapter in which the crew uses the planet’s gravity as a slingshot to speed them along to Saturn. It is a harrowing episode, but Clarke’s imagination outpaced the abilities of special effects artists of the era. No one could create a Saturn that Kubrick found convincing, so rather than render a set of third-rate rings, the perfectionist filmmaker simplified the story. The monolith’s signal stopped now in the Jovian system, and all that followed did so in Jupiter’s orbit.41 The plots more or less converge there.
This small science-fiction factoid might have been consigned to the back of a Trivial Pursuit card were it not for the sequel, 2010: Odyssey Two, written by Clarke and published in 1981. Here the author faced a dilemma. Should he pen the story as a sequel to his novel, or to the film, which was released first and known more broadly? Did Dave Bowman, lone survivor of the computer HAL 9000’s psychotic break, abandon Discovery One in orbit around Saturn (at the moon Iapetus), or around Jupiter and one of its moons?
Clarke chose to write the novel as a sequel to the film. Odyssey Two opens with the Chinese spacecraft Tsien landing on Europa, its taikonauts trudging across the icy world on a reconnaissance mission for sources of water—a vital commodity if humans are ever to settle space. Before they can complete their task, however, some sort of evolved sea life emerges from a crack in the Europan ice shell, destroys the landing vessel, and slays every taikonaut but one, whose final, frantic message to Earth is: “. . . relay this information to Earth. Tsien destroyed three hours ago. I’m only survivor. Using my suit radio—no idea if it has enough range, but it’s the only chance. Please listen carefully. THERE IS LIFE ON EUROPA. I repeat: THERE IS LIFE ON EUROPA.”42
The novel ends with a mysterious message to Earth from an unknown celestial entity:
ALL THESE WORLDS ARE YOURS—EXCEPT EUROPA. ATTEMPT NO LANDINGS THERE.
THE PROSAIC PRESENT remains squidless. Planetary science is a plucky upstart as far as scientific disciplines go, belonging once exclusively to the field of physics, and then to astronomy, and, since the start of space exploration, to geology. (As spacecraft and their scientific instrument payloads—the tools they carry that collect the data—evolve in sophistication, the fields of chemistry and biology will grow increasingly vital to the discipline.) To do geology, you need access to, or images of, hard surfaces. You need to see rocks and ridges and rubble and regolith. You can work backward. The snake looks like an ancient riverbed. Those stones, smoothed, get that way when water rubs rock. That’s a volcano, that’s a gorge, that’s a cliff. It’s easy on Earth because you can just look down and start studying, but before the rise of rockets, Mars existed only through telescopes, a smear of fire with ice caps on each end, and Venus was veiled in teal and impenetrable clouds.
It was the Apollo program that really made geologists tilt their heads upward in unison and ply their trade to untrodden worlds. Down in Alabama, Wernher von Braun, the exfiltrated German genius of rocketry, built the biggest booster ever to lift Luna-bound star voyagers. But nobody was sure, exactly, what the moon was made of or how hard its surface might be. What if we looked up each night to a lunar surface not of solid rock but of soft dust accumulated over billions of years and almost entirely undisturbed? What if the Eagle landed, and just . . . kept landing! Just sank right into the moon as though its surface were a powdery snowbank. While precursor robotic reconnaissance spacecraft had touched down on luna firma, would every part of the moon be like that? Oh, but it was even worse. What if the Eagle didn’t sink—what if astronauts set up Tranquility Base, walked around, planted the flag, and called the president, but when they climbed back into the lander, what if the moon dust was flammable? They’d pressurize the Eagle, and boom: Mare Tempestatis. NASA needed geologists to sharpen their pencils and solve the problem most ricky-tick—and to the great relief of Apollo astronauts, they did. The magnitude of the achievement of geologists to understand an orbiting ancient alabaster rock was reflected in the second thing Neil Armstrong said, after taking a giant leap for mankind:
“And the—the surface is fine and powdery. I can—I can pick it up loosely with my toe. It does adhere in fine layers like powdered charcoal to the sole and sides of my boots. I only go in a small fraction of an inch, maybe an eighth of an inch, but I can see the footprints of my boots and the treads in the fine, sandy particles.”43
And planetary science was off to the races.
Bob Pappalardo entered that race in earnest twenty years after taking a desk in Carl Sagan’s classroom, with Jet Propulsion Laboratory beckoning him: Come to California. Set up a Europa laboratory. Help us build a proper program on Europa. Help find that life. You won’t get there from Colorado, Bob. Are you interested?
Yes, Bob said. I am interested.
Seventeen months of negotiations followed. They weren’t tense, exactly, but they were tedious: title, lab facilities. He wanted a salary such that in Los Angeles, he could buy a house similar to the one he had in Lyons. That delayed things. I mean, what does a house in Colorado cost? How much? You’re not getting a house that size for that money in L.A.! You’re not getting a house that size in L.A. for double that price.44 So there was a firm but gentle and sometimes terse but generally respectful back-and-forth. Ultimately, the numbers fell in Bob’s favor, but there was one more thing he wanted.
During preliminary discussions, the lab teased the prospect of Bob being the project scientist of a Europa mission—its leader, in other words—should a mission go forward. This was so far outside the scope of the career Bob had imagined for himself that it veered into areas incomprehensible. Before the lab came calling, Assistant Professor Pappalardo’s goal—he’d written it down and everything in one of those what-do-you-want-out-of-life? workbooks you find in the self-help section of bookstores—was to be the lead scientist on a camera carried by some spacecraft that might one day return to Jupiter. He wasn’t even asking to be Spock; Gene Roddenberry would have listed him in the credits as Blue Shirt Crewman #3, maybe. It was still an enormously ambitious goal—any scientist’s crowning professional achievement. But to be project scientist? Look, one flagship launches every decade. And there’s only one person who gets to be project scientist. It would be far easier, statistically, to be an astronaut—NASA employed about a hundred of those, versus maybe five or so project scientists to launch a flagship mission to the outer solar system, and not “at the time,” but ever. Part of it was because the outer planets were so aptly named—Jupiter (the nearest outer planet) was one wire past Mars on the classroom solar-system-around-the-yellow-lightbulb model, but took vastly longer to reach. Pregnancies lasted longer than a trip to Mars, but by the time a spacecraft reached Jupiter, the same child would not only be born, but would be old enough to play on a youth soccer team.
Which made Mars an enticing object of exploration—more so, even, because every robotic Mars mission could be framed as a precursor for human exploration. And though astronauts hadn’t touched a celestial object beyond Earth since the last Apollo flight in 1972, NASA was thoroughly and indelibly an astronaut-led, astronaut-centric organization, and Mars its elusive but inevitable target post-Apollo.
Programmatically, the Red Planet was an enterprise unto itself at the agency and competed against only itself for flight projects. Every twenty-six months, as orbits aligned, something would launch for Mars. For every other object in outer space, however, it was urban warfare. Headquarters was, on a good day, apathetic to aspirations for an outer planets flagship (the outer planets as in all of them, and their hundreds of moons of fire, ice, rock, and metal) and, ordinarily, entirely antipathetic if not actively antithetical. As a result, the outer planets competed against not only themselves as worlds worthy of exploration (e.g., Do we go next to Io or Iapetus?), but also against every other object in the solar system. You wanted a flagship to Neptune, you had best be better than Venus. You wanted a Triton orbiter, and you’re crossing swords with Mercury, Ceres, or Saturn. NASA selects a spacecraft to study an asteroid or comet, and it is never Mars that will want for hardware on the launch pad; it’s Europa or Titan or even the moon. And if you were a non-Mars researcher, you couldn’t help but feel some irritation? annoyance? envy? Look, the Mars community labored mightily for its success, and if you studied the outer planets or Venus or the giant asteroid Vesta, you probably, in fact, worked on one Mars mission or another, or did research on Mars data, because the grant money was there and your car payment was due next week. Despite an unbroken chain of NASA budget squeezes and shortfalls going back to the end of Apollo, everyone needed Mars to prosper because it was like social security for solar system scientists. The government might meddle, but it would never kill it. Places like NOT MARS, however, were always maybes, always if-we-can-afford-its.
Then again, you never knew. And if some sympathetic functionary at NASA headquarters got traction and convinced the right person to give Europa a chance, Bob wanted it in writing that he would be the project scientist of that mission.45 JPL management personnel didn’t say no, but they couldn’t say yes on paper. They could, however, formally declare that he would be their top candidate for project scientist should a mission go forward. It was a sign, at least, that they were serious, and Bob signed on the dotted line. Three years, he figured, and NASA would want his mission. As the lone survivor of the Tsien could attest, however, Europa would not prove so hospitable to callers.
In the end, it would take seventeen years, six major studies, multiple missions approved, multiple missions abandoned, friendships formed and enmities established, funding raised and budgets lost, congressional hearings, unlikely alliances, technological breakthroughs, terrible losses, and stunning discoveries to get NASA to make it official.46
But much of that was yet to come. A contract signed, Bob Pappalardo packed his life and his cat and pointed his car westerly—one more northeasterner with his sights set on Pasadena. He had once missed a total solar eclipse, but that was OK. They could have the sun. In 2006 the child of Trek was California bound. This time, he was after a moon.