by Alan Stern
Alan was surprised by Briggs’s immediate, unhesitating, and positive response: “You know, no one’s ever asked me about that before. It’s a wonderful idea: we should do that.”
DINNER AND A MOVEMENT
Everything starts out somewhere, and big things sometimes start out very small. The origin of what ultimately, much later, would become the almost-billion-dollar New Horizons mission to Pluto, happened one night in May of 1989 in an unremarkable Italian restaurant in Baltimore’s Little Italy neighborhood. A large contingent of planetary scientists were in town for the first ever AGU Pluto session, featuring a dozen talks by an impressive coterie of scientists. The session was attended by a hundred or more other scientists and generated good buzz. Alan and Fran, knowing that all the key Pluto people would be there, wanted to strike while the iron was hot. So they arranged for a core group to have dinner together the evening after the Pluto session to discuss how to go forward toward a mission. Alan, Fran, Marc, Ralph, Bill, and nine other scientists were there. None of them could imagine then that something historic was being hatched that evening.
Over meatballs, pasta, and Cabernet, the dinner group started talking about what it might take to send a mission to Pluto. The task was clearly daunting. No Pluto mission was on the drawing board at all, and there were numerous other missions already in line, each waiting their turn to fly. Each had its own constituency of advocates. There were the Mars people, the Venus people, those working on Cassini—the promised (but expensive) big ticket Saturn-orbiter mission—and those who dreamed of returning a sample from a comet. Each had impressive plans for missions that were long overdue. But NASA’s budget was so limited that only two new planetary missions had been started in all of the 1980s.
The dinner group knew they were out of their depth, but they shared a conviction that a Pluto mission was an important idea that somehow needed to happen. Alan had been working on a plan of attack, and the group was all ears. He recounted his meeting at NASA Headquarters with Geoff Briggs and the amazingly easy path he found to get agreement for a mission study.
The next question was: How could they rally the planetary scientific community to show NASA that a Pluto mission had broad support? They brainstormed ideas and formed a plan to build cred and buy-in. They scribbled action items on napkins. One was to publish a special issue of the Journal of Geophysical Research showcasing the research results from that day’s AGU Pluto session. Another was to work to excite the people they knew at NASA Headquarters, to follow up on the idea of sponsoring a mission study. They would also start to recommend Pluto mission supporters for the various committees that advise NASA about planetary mission priorities. And they would organize a letter-writing campaign to cajole colleagues to contact NASA and express support for a mission.
It helped that the Plutophiles were mostly young and at the start of their careers. For these ambitious space nerds in their twenties and thirties, who had grown up on Apollo, Mariner, Viking, and Voyager, the thought of upending the established order with an insurgent Pluto mission was more than a little crazy, and also thrilling. Even if they were tilting at windmills, it would be fun. They loved the idea of defying the odds and bucking the establishment.
It wasn’t that night that they started calling themselves the Pluto Underground. In fact, nobody remembers exactly when the name arose, but it began to be used and was fitting in many ways. It started, no doubt, as a play on the term “Mars Underground,” a group of passionate scientists and space enthusiasts who had been shaking up NASA with imaginative and aggressive plans for human bases on Mars. The Mars Underground has helped goad NASA into planning a new generation of Mars missions. If anything, though, the “underground” tag was even more apt for the Pluto fanatics. Because a mission to Pluto was, at first, a subversive and unlikely idea, cooked up by a rebel alliance that seemed ill-equipped to take on an empire.
Marc Buie remembers coming away from that Italian dinner with a changed view and an assignment to act:
I consider that dinner to be a pivotal moment. That was the turning point where it all went from just gee-whiz hallway conversations to a larger, more systemic plan of attack to try to accomplish something. I left with a task: to start a grassroots letter-writing campaign to NASA by other scientists. I went back to my office and I wrote a letter that I sent out to everybody I could think of in the field, young and old, encouraging them to write letters to NASA Headquarters saying, “We really ought to think about going to Pluto.”
The letter-writing movement that Marc was assigned was a bit of an end run, going outside the normal NASA advisory process, or at least gaming it a little. And it was typical of the ad hoc, guerrilla nature of their movement. It also got Marc in hot water. He was a junior scientist at the Space Telescope Science Institute in Baltimore, where he was the point person for all the planetary observations on the Hubble Space Telescope. Marc’s “Dear Colleague” letter came to the attention of his boss, Riccardo Giacconi, the powerful and intimidating (and soon to be Nobel Prize–winning) director of the entire Space Telescope Science Institute: “He called me into his office and really lit into me over that campaign and accused me of lobbying. I said, ‘I know what lobbying is and that’s not what this is. I should be able to talk to my colleagues about my scientific interests.’”
Buie’s letter-writing campaign generated dozens of appeals to NASA, so the Pluto Underground’s rabble-rousing quickly started to have an effect. The biggest planetary science meeting every year is the “DPS meeting,” which is shorthand for the Division of Planetary Sciences of the American Astronomical Society. At the DPS meeting that fall, NASA held an evening session in which their officials presented future mission plans to the planetary science community and sought input. Geoff Briggs stood up and told nearly one thousand planetary scientists how NASA Headquarters had been flooded with letters urging it to study a mission to Pluto. As he described it, such strong community interest took NASA by surprise, and NASA was starting to take it more seriously.
As a result, right around the time of that DPS meeting, just four months after Alan had approached him at NASA Headquarters to do a study, Briggs funded the first official NASA study of a possible Pluto mission. He asked Alan, fresh out of grad school, and Fran, just teaching her first class as a professor at Boulder, to be the lead scientists of that study, pairing them with a highly experienced and brilliant NASA engineer a generation older: Dr. Robert Farquhar, who would manage the study. It was a good sign: Farquhar had a legendary reputation as an innovative and visionary mission designer.
The timing dovetailed fortuitously with another wave then washing through NASA’s planetary mission culture, recognizing that the program needed more small missions.
Given budgetary reality, there just wasn’t the money to afford new big missions like Voyager. Why? Galileo and Cassini, NASA’s next two big approved missions, each multibillion-dollar giant-planet orbiters, were both experiencing major problems at the time. Galileo had just been launched on its way to orbit Jupiter, but it had issues. The main antenna was broken and the data rate back to Earth had to be drastically reduced, lowering goals and expectations for what it could achieve. Cassini—a Saturn orbiter NASA was then building—was next, but its costs kept ballooning and there was a serious threat of cancellation. These missions were—in the lingo of the profession—“Christmas trees,” meaning they were loaded with so many capabilities and scientific instruments, which resulted in those multibillion-dollar price tags.
In the fiscal climate of the early 1990s, any more such missions were simply nonstarters. Instead, Briggs and others at NASA encouraged the development of smaller, cheaper, better-targeted missions with more modest payloads containing far fewer instruments and capabilities, encouraging creative thinking of ways to do ambitious missions with smaller price tags.
Farquhar’s Pluto mission study ran for a year, wrapping up in late 1990. It was called “Pluto 350,” and it was focused on a small, 350-kilogram spacecraft weighing j
ust about half what Voyager had. The resulting design included a much smaller instrument payload than Voyager’s, but with more-compact and modern instruments designed to maximize science per pound, including a camera and infrared spectrometers to photograph and map Pluto’s surface, an ultraviolet spectrometer to examine the atmosphere, and a plasma instrument to measure interaction with the solar wind.
Farquhar (who, sadly, died in late 2015, shortly after witnessing the Pluto flyby just months before) was a genius of orbital mechanics and had a legendary knack for finding crafty solutions to get from planet to planet with less fuel than others thought possible, primarily by using clever gravitational assists. One of his innovations that greatly lowered the anticipated costs of the Pluto 350 mission was to plan a launch on a relatively small rocket, a Delta II. A liability of this plan was that it wouldn’t have enough velocity to fly straight to Jupiter for the gravity assist toward Pluto. Instead, in Farquhar’s scheme, Pluto 350 would first go inward toward the Sun, use gravity boosts from Venus and then also Earth to get out to Jupiter, and then on to Pluto. This enabled a smaller rocket to do the job of getting to Pluto, but it meant the Pluto 350 craft would be in space for fifteen years en route to Pluto and would have to take the heat near hot Venus before the long journey out to cold Pluto. It was not the ideal way to go, but it kept costs within the tight mission box the study team was aiming for, and the sheer ingenuity of it turned heads.
The mission plan was featured that fall in a widely read article by Farquhar and Alan called “Pushing Back the Frontier: A Mission to the Pluto-Charon System,” published in Planetary Report, the lavishly illustrated and slickly produced newsletter of The Planetary Society, an organization with tens of thousands of members, started by Carl Sagan largely to galvanize public support for increased planetary exploration. The article began, “In the past three decades humanity has sent spacecraft to all the planets in our system except Pluto,” and ended, “Whether humankind is willing to devote the resources to explore this fascinating pair of worlds [Pluto and Charon] is unknown—it is something we must decide.”
The piece made a compelling case for why we must explore Pluto, why the time was right, and how the Pluto 350 study proved it could be done with a small and low-cost mission. Alan and Farquhar hoped that by placing the article before the Planetary Report readership they could help generate both public interest and Planetary Society lobbying support for a Pluto mission.
Around the time their Planetary Report article was published, a NASA press conference was held to announce the Pluto 350 study results. Alan and Fran and several others were invited to give talks about the scientific potential. The event was unusually well attended, and NASA began to notice that, as at AGU and DPS, Pluto always draws a crowd.
In front of the microphones, and in the glare of flashbulbs and television lights, members of the Pluto Underground looked at each other in disbelief at all the fuss. Goal number one had been accomplished. They were aboveground now, and with a proof-of-concept mission design. But goal number two was more daunting: Could they convince NASA to start a more serious and comprehensive mission study that might actually turn into funding for a mission?
3
TEN YEARS IN THE WILDERNESS
A NEW START?
Onward to the outer solar system! After the success and the buzz of the Pluto 350 study, the Plutophiles felt the wind at their backs, pushing them outward toward the uncharted trans-Neptunian depths, the terra incognita of our planetary system. For a moment it seemed like smooth sailing.
But their dreams and machines could not leave Earth without first navigating a perilous terrain that these young scientists were scarcely prepared for, or familiar with. Before any interplanetary trip could be launched, they first had to navigate “the beltway”—the complex political landscape surrounding Washington, DC—where the money is allocated for deep-space exploration. They had to traverse through and triumph over that DC funding swamp, and this part of their quest would ultimately prove longer, and was in some ways more arduous, than the journey from Earth to Pluto itself.
Shortly after the Pluto 350 press conference, Alan and Fran went back to NASA Headquarters and sat down with Geoff Briggs and other NASA officials to address what the next steps should be to turn it into a real mission. In the lingo of the trade, what they ultimately needed was an approved project, called a “new start.”
Mission concepts are always being conceived, ranked, and studied. But what really counts is when NASA commits to a mission by putting it in its budget and proposing it to Congress. Only then—when the funding to design and build it is allocated—does a project achieve a new start. The officials at NASA told Alan and Fran that to warrant a new start, they would need the endorsement of the Solar System Exploration Subcommittee, the SSES.
HIGH COUNCIL
Within the universe of NASA mission politics then, there were a few key advisory committees that were crucial in getting a green light for any new project. Even the best plans fail if they do not pass these hurdles. In the 1990s and early 2000s the most influential group advising NASA on planetary mission strategy and new starts was the SSES; to go anywhere in the solar system, a mission had to get their approval.
It wasn’t quite like the Jedi High Council, where Yoda and the wise elders meet in a grand chamber with magnificently sloping windows looking over the planet of Coruscant, deciding matters of galactic importance—but for NASA planetary missions back then, the SSES was as close as it got. The dozen or so NASA-appointed advisors of the SSES usually met in comparatively bland, windowless, rectangular conference rooms at NASA Headquarters in Washington, DC. These were not all-knowing masters, but scientists taking time out of other professional duties to make recommendations on planetary exploration strategy. And there were always many more good ideas than available funding.
Mostly, the SSES committee members listened to reports detailing what various missions could contribute to the field, and how much each would cost, then they ranked and debated priorities, and prepared “roadmap documents.”
In late February 1991, the SSES was asked to pass judgment on the concept of a Pluto mission. They had received the Pluto 350 report and a document written by Alan, Fran, and colleagues describing the detailed scientific rationale for exploring Pluto and presenting a list of scientific questions that Pluto 350 could resolve. A sampling of those questions included:
How does Pluto compare with Neptune’s planet-size moon, Triton? Are they really twins left over from an early massive population of icy dwarf planets?
Is Pluto’s surface composition as varied as its surface markings seem to indicate? Is it really made out of completely different materials in different areas?
How deep and mobile are Pluto’s volatile ices? Are they merely a thin coating plated on the surface, or do they really form a deep, icy crust?
Could Pluto be internally active?
How does the geology of Pluto’s moon, Charon, compare with Pluto’s?
What is the structure of Pluto’s atmosphere? How quickly is it escaping from the planet?
How do Pluto’s strong seasons affect the surface and atmosphere? Can seasonal effects explain the high surface contrasts and the visible differences between the northern and southern polar caps? Can they explain why Pluto is darkest on the side directly facing Charon and brightest on the opposite hemisphere?
What is the origin of the Pluto-Charon binary? Did the binary require a massive impact event to form it, like the one that created the Earth-Moon system?
In their reports to the SSES, the Plutophiles demonstrated convincingly that a well-equipped flyby mission could revolutionize knowledge of Pluto, addressing all these compelling questions, and more. Their case had been almost two years in the making; it was solid and could not be ignored. The chair of the SSES at that time was Jonathan Lunine, a young and impressively accomplished, brashly confident, and widely respected professor from the University of Arizona, who was himself a barely closeted P
lutophile. Yet some on the SSES felt that a Pluto mission was not ready for prime time, that the idea had risen too quickly from obscurity to deserve consideration alongside other concepts that had long been under development. Others worried that it would take far too many years to accomplish and that with limited resources NASA should focus on projects promising faster payoffs—meaning shorter flight times to closer locales.
Fortunately, strong and influential voices got behind the idea of a Pluto mission. Geoff Briggs, who, as chief of Solar System Exploration at NASA, had given Alan such an important foot in the door, had stepped down. His successor, Wes Huntress, was an accomplished planetary astrochemist who had worked for many years studying planetary atmospheres at JPL before being promoted to NASA Headquarters to run the Agency’s planetary program. At the February 1991 SSES meeting, Huntress argued that given the obvious pairing of scientific and public interest, Pluto should be among NASA’s highest priorities for a new start.
But despite Huntress’s support, a debate erupted at the SSES between the Pluto supporters, who were mostly younger scientists, and Pluto detractors, mostly older scientists. Alan recalls that in that debate, one key older voice stood out for Pluto, that of sixty-eight-year-old Donald Hunten. Among planetary scientists, Hunten—an atmospheric physicist—was a living legend, responsible for much of the mathematical machinery used to describe and understand the workings of planetary atmospheres. A reserved, no-nonsense Canadian, he was an imposing presence. His voice was a low, gravelly growl with only two volume settings: barely audible most of the time, or very loud when he was riled. Though he could be intimidating, Hunten had a reputation for rigor and fairness, and he was one of those people whose opinion everyone valued because he had impeccable scientific intuition: simply put, Hunten knew so damn much, and he seemed to always be right.
At that SSES meeting, Hunten got up and spoke at a crucial time in the debate, after Alan had come under attack for pitching the Pluto mission for the next new start. Someone argued that Pluto could wait because Mars was more important and easier to reach, so Hunten stood up, eyed the room, and summarized all the compelling scientific reasons for a mission to Pluto. Then he declared in his louder, shouting voice, “God damn it! I don’t expect to be alive when a mission arrives at Pluto, and if I am alive, I don’t expect to be aware of the event. But this is what we should be doing. The science is important. Let’s get on with it.”