by Adam Frank
Before Drake, the scientific consideration of exo-civilizations was unfocused. What existed was a mix of unconnected musings in scientific journals, books, and popular articles. There was no structure for building a coherent program of study, either through theory or observations. By breaking the big question into seven smaller questions, Drake crafted a useful way to think about the problem that also left scientists something they could work on. It gave them something to do.
Each of the terms in the equation could be explored on its own, using whatever means were available. Astronomers could work on the first three terms; biologists could think about the two that followed; sociologists and anthropologists could explore the last two. Of course, most of the work would be speculative. But at least it would be speculation with a focus and a scientific foundation.
With time and patience, advances were made from all sorts of directions. Computer studies of chemical reactions provided insights into abiogenesis. Evolutionary studies of life on Earth showed how cognitive patterns leading to intelligence first appeared. And while some terms, like the average age of a civilization, might never be known, others, like the fraction of stars with planets, were thought to be within grasp at the time of the Green Bank meeting. In addition, while even the closest stars were fifty trillion miles away, the planets in our solar system were relatively close. If we could find even one example of life—in its simplest form—on Mars or anywhere else in our solar system, that would tell us something powerful about the first biology term.
What Drake’s equation gave astrobiology was a way to think about itself. In the process, it changed how we understood life, civilization, and ourselves.
Drake’s equation also ensured the success of the Green Bank meeting. Beginning with the rate of star formation and marching all the way through to the average lifetime of technological civilizations, the nine participants did their best to make informed estimates of the different terms. History shows they were a hopeful group. They assigned values relatively close to one for all the fractions. Most telling, though, they reserved their pessimism for Drake’s final factor: the average lifespan of technological civilizations.
The capacity for a civilization to short-circuit its own evolution through self-destruction vexed the meeting’s participants. It would go on to become a bottleneck in all thinking about searches for extraterrestrial intelligence (SETI). The Green Bank participants believed, as Drake later wrote, that “the lifetimes of civilizations would either be very short—less than a thousand years—or extremely long—in excess of perhaps hundreds of millions of years.”57
In the end, the group agreed that the final factor was what mattered most. The number of stars was so vast that the galaxy could absorb a lot of what Drake and his colleagues considered pessimism regarding the other terms of the equation. But the galaxy also needed to be populated now. There needed to be an overlap in time between our civilization and theirs so that there would be signals for us to receive. That meant the other civilizations needed to last at least millions of years, which seemed like a stretch for the Green Bank group.
Just before the meeting ended, Drake and his colleagues broke out their one remaining bottle of champagne (Calvin’s call from the Nobel Committee had come late on the first night of the meeting). As they raised their glasses, Otto Struve offered a toast. “To the value of L,” said Struve. “May it prove to be a very large number.”58
THE DAY CLIMATE CHANGED
In 1965, little more than three years after Struve’s toast, President Lyndon Johnson would raise the same issue of civilizations’ longevity in the far more specific context of our own fate. Speaking before a joint session of Congress, he said, “[T]his generation has altered the composition of the atmosphere on a global scale through . . . a steady increase in carbon dioxide from the burning of fossil fuels.”59
It’s remarkable to note that, more than fifty years ago, an American president was already aware of, and acknowledging, human-created climate change. Johnson had been briefed on the dangers of CO2 increases by the famous climate scientists Charles Keeling and Roger Revelle, among others. So, not only was President Johnson aware of the issue, but he was already concerned enough to raise it before Congress. That single sentence in his address gives the lie to the claims of so many climate-change deniers that global warming is some kind of recent hoax. Indeed, the scientific understanding of our effect on the Earth dates back more than a century. As President Johnson’s speech demonstrates, even fifty years ago, that understanding was firm enough to gain notice at the highest levels of policy and politics.
But there is a difference between a community of scientists, at the vanguard of their fields, glimpsing human-driven climate change and the culture as a whole metabolizing the story. A single speech by a president can’t create the kind of intimacy that is the hallmark of humanity’s most powerful narratives about itself and its place in the world. That takes time and the play of events. The industrial revolution, for example, didn’t arrive as soon as the first factory was built. It took people moving en masse from farms to cities where day-to-day life took on new rhythms and textures. Only then did we begin to see ourselves as “industrial.” Only then could we tell new stories about ourselves as a civilization that conquered the planet with steel, rubber, and oil.
Likewise, we are just beginning our entry into the Anthropocene. Fifty years on from President Johnson’s speech, we have just started becoming familiar with images of melting glaciers, massive heat waves, and flooded cities. We are just beginning to experience what life on a climate-changed world looks like. But when President Johnson stood before Congress in 1965, that story was still new.
Conservation was the intended theme of the president’s speech that day. Only a few years had passed since biologist Rachel Carson had raised alarms over the environmental effects of pesticides in Silent Spring. Even less time had elapsed since the treaty banning atmospheric testing of nuclear weapons had gone into effect. While the Cold War made instant annihilation a credible threat in the 1950s, by the mid-1960s some were beginning to realize that even the everyday activities of our project of civilization were not, in total, going unnoticed by the planet.
Sustainability on a global scale, however, is a very different kind of story for humanity to tell itself. It demands a vastly enlarged imaginative palette. At the time of President Johnson’s speech, the picture of a climate-threatened future was just starting to be painted by scientists as they gained a first foothold on understanding the Earth as a planet. These researchers were recognizing, for the first time, that Earth needed to be understood in its entirety as single, tightly coupled system—a kind of vast, planetary-scale machine.
Ironically, and as is so often the case, the need for this new vision found its first urgency in the needs of warfare. With the rise of long-range bombers and intercontinental missiles, cold warriors were busy imagining Earth from well above the atmosphere. But they were also deeply concerned with how weather could tip the scales of battle. It was partly at their urging that resources poured into the scientific study of climate. A nuclear-powered laboratory was built under the ice of Greenland to understand how weather patterns changed over the course of millennia. Instrument-laden ships crisscrossed the oceans, studying the forces driving deep ocean currents. Most importantly, the same ICBMs threatening nuclear war were starting to lift scientific satellites into orbit, where their eyes would point downward to study the Earth.
These were expensive and globally extensive efforts. They laid the groundwork for a new vision of our project of civilization’s planetary context and impact.
The first photograph of Earth captured by a weather satellite, taken in 1960.
In 1960, a still-wet-behind-the-ears NASA launched its first successful weather satellite, TIROS (Television Infrared Observation Satellite). By 1962, TIROS was offering continuous coverage of the Earth’s weather.60 In the wake of TIROS, no longer would a hurricane unleash its violence on an unsuspecting populat
ion. And for the first time, people were treated to images of Earth as a globe suspended in space. Even the earliest grainy videos showed the elegant arc of the world’s horizon as seen from high above the atmosphere, a vision that would rewire our collective imaginations.
By the mid-1960s, a convergence had begun. Images from TIROS, President Johnson’s address on carbon dioxide, Fermi’s lunchtime insight, and Drake’s Green Bank conference were pieces in a cultural jigsaw puzzle that was beginning to assemble itself. Each represented a tentative first step toward seeing our project of civilization in a new light—the light of the stars. Fermi and Drake represented a new awareness among scientists that the story of our own project of civilization must be set onto a cosmic stage, with all its stars, planets, and possibilities. Meanwhile, studies of climate funded via Cold War urgencies shaped an awakening among other scientists that Earth’s story must be told in terms of a mighty planetary system driven by sunlight and shaped by life—including our own. Finally, President Johnson’s address signaled that our civilization’s impact on the planet was making its way into the domains of culture and politics.
A new human story, a new human mythology, was emerging. The outlines of this narrative, in which human beings and our project would be inescapably bound to the machinery of planetary evolution, were beginning to take shape. Few at the time could recognize the power, the peril, and the promise growing in this new story. It was still too new and too unformed. To take the next steps in forging this new vision, we would have to leave home. We would have to become wayfarers and journey, for the first time in our long history, out to the high frontier of space. That was where the sibling worlds of our solar system were waiting to tell us their secrets.
CHAPTER 2
WHAT THE ROBOT AMBASSADORS SAY
TO BE A BUM
The Florida sun glistened over the blue Atlantic waters, but Jack James was in a black mood. It was July 22, 1962, and it had been a very bad day. The Texas-born engineer was project manager for NASA’s Mariner program, which aimed to send America’s first emissary to another planet. James had gotten the job a little more than two years earlier. Like everything else in the space race of the early 1960s, James’s program had been rushed forward at breakneck speed, working nonstop. Now the fruit of all that effort lay in ruins at the bottom of the ocean.
James and his team had been given less than fourteen months to design, build, and launch a probe to Venus.1 Until then, the Moon had been the primary target of the space race, and America’s record for hurling oddly shaped boxes of electronics at Earth’s rocky satellite had been a mixed bag. The Russians were having better luck. They’d gotten three of their nine probes to the Moon. The US had only gotten one there.2 Now NASA was desperate for more than a win. It needed to upstage the Soviets in a big way. That’s why James was given the audacious job of thinking beyond the Moon and going interplanetary.
Rocket engineer Jack James (right), with Mariner Project manager Dan Schneiderman (left).
Mariner 1 was designed to perform a “fly-by” past Venus, a world that orbited 30 percent closer to the Sun, but with almost the same mass and size as Earth.3 The probe’s original design called for 1,250 pounds of scientific instruments, communications gear, solar panels, rocket motors, and fuel. But the new, more powerful generation of rocket boosters Mariner was supposed to ride into space kept blowing up, and NASA brass soon demanded a redesign. James’s engineers were forced to quickly shed more than two-thirds of Mariner’s weight.
James navigated his team through every design change and every challenge. That was how they came to this day. With the whole world watching, Mariner 1’s booster rocket lit up the Florida sky as it blasted off that July morning. For the first few moments, the launch looked clean. But then the Atlas booster began to fishtail. Every launch has a “range safety officer” whose job is to blow the rocket to bits if it looks as though the mission is failing and it’s going to crash back to Earth. Four minutes and fifty-three seconds into the flight—and just six seconds before Mariner 1 would have safely separated from the main launch vehicle—the safety officer hit the big red button.4
Boom!
For a full minute after the rocket exploded, telemetry continued to get signals from the probe as it tumbled from the sky to its ocean grave.5 At least Mariner 1 had been a tough bird.
They’d been so damn close. Just six seconds more and they’d have been on their way to Venus.
“Born to Lose,” by Ray Charles, played on the radio as James drove back to his rented apartment in Cocoa Beach. He was in despair. Years later, he’d recall the mantra of all space engineers: “To be a hero there are ten thousand parts that need to work properly on a spacecraft. To become a bum you just need one of them to fail.”6
But while James and his team were down, they weren’t out. The now-destroyed probe had a twin. Mariner 2 was waiting back at Cape Canaveral.7 There was still time to be a hero.
THE VENUS PROBLEM
The logic of the space race dictated that either Mars or Venus would be the next destination after getting probes to the Moon. Both were neighbor planets that could be reached in a matter of months, a step up from the three-day trip to the Moon. And each had its own long history of dreamers imagining a temperate world fit for extraterrestrial life.
Given its proximity to the Sun, Venus gets twice as much solar energy as Earth.8 That’s why many early astronomers imagined Venus as a jungle planet. In 1870, Claude Flammarion (the author of The Plurality of Worlds) thrilled his readers with images of a Venusian landscape made of broad, swampy plains ringed by mountains higher than the Himalayas.9
Flammarion assured his readers that Venus was a world rich with life: “Of what nature are the inhabitants of Venus . . . ? All we can say is that the organized life [there] must be little different from terrestrial life, and that this world is one of those that resembles our own most.”10
An imagined view of Venus from Flammarion’s 1884 book, Les Terres Ciel.
But with the increasing power of astrophysical observations, this pleasant dream of a jungle Venus would come under fire. First, astronomical observations in the late eighteenth century revealed Venus to be perpetually shrouded by clouds.11 Then, in the mid-twentieth century, the Venusian atmosphere was revealed to be heavy with carbon dioxide (CO2). The Earth’s atmosphere is 78 percent nitrogen, 21 percent oxygen, and one percent everything else. CO2 comes in at a mere 0.039 percent of the air you are breathing right now. That’s a pretty small fraction for a molecule that, as we will see, has a big role to play in our story. But for Venus, CO2 is pretty much all there is to the atmosphere, accounting for more than 95 percent of all its gases.12
The presence of so much CO2 was bound to make Venus a very different place from Earth, and by 1956, astronomers had gained their first evidence of just how different it might be. Using the same kind of radio astronomy technologies Frank Drake would soon employ in Green Bank, scientists from the Naval Research Laboratory found evidence that Venus’s surface temperature was well above 600 degrees Fahrenheit.13 That’s hundreds of degrees above the boiling point of water. If the NRL result was true, then Flammarion couldn’t have been more deluded. His Venusian swamps would have boiled away long ago. More importantly, 600 degrees was far too hot for any form of life to survive. It seemed the place Venus resembled most wasn’t Earth, but Hell.
While geology and its study of the Earth had been around a long time, planetary science—which takes all planets as its subject—was a young field. The NRL results set off a firestorm among the small group of researchers who considered themselves planetary scientists. Part of the conflict came because, just a few years earlier, another team had predicted Venus to be covered by a vast, planet-girdling ocean.14 But neither oceans nor lakes nor even cups of tea could be squared with the new NRL data, which suggested temperatures on Venus comparable to the inside of a pizza oven.
In response, some scientists claimed the NRL’s data had been misinterpreted. Its source,
they claimed, wasn’t Venus’s surface but violent, atomic-scale processes occurring at the boundary of its atmosphere and the harsh conditions of interplanetary space.15
Resolving the dilemma required more power than earthbound instruments could provide. The best telescopes of the day could not see the disk of Venus in enough detail to distinguish between a hot surface or processes occurring high in the atmosphere. Getting up close with a space probe was one means of getting that level of detail.
But a space mission wasn’t the only key that astronomers needed to unlock the mystery of Venusian climate. The NRL result was shocking to scientists because no one could understand how it might be true. Venus is closer to the Sun, but that proximity should only raise its surface temperature a few tens of degrees, not hundreds.16 If the surface temperatures really were 600 degrees, how could a planet so like the Earth in so many ways have ended up so different from our world? What was needed was a theory explaining how Venus might end up with such insanely high temperatures.
That task would be taken on by the young, untested, and not-yet-minted PhD student Carl Sagan. Though no one at the time could have guessed it, not only would Sagan’s work solve the Venus problem, it would also set the stage for a deeper understanding of our own world’s entry into the Anthropocene.
THE GREENHOUSE EFFECT
Though he died in 1996, Carl Sagan remains one of the most recognizable scientific faces in the popular imagination. Born sixty-two years earlier to working-class Jewish parents in Brooklyn, Sagan’s love affair with science began as a young boy during a trip to the 1939 World’s Fair. The passionate interest in life on other planets that defined his life came a bit later, as a teenager, with a steady diet of Astounding Science Fiction magazine and writers like H.G. Wells.17
