“But the fact that some geniuses were laughed at does not imply that all who are laughed at are geniuses.”
CARL SAGAN
The quest to find life in space is as old as our loneliness. The Greek philosopher Metrodorus, in the fourth century BC, offered that “to consider the Earth as the only populated world in infinite space is as absurd as to assert that in an entire field of millet, only one grain will grow.”1 From very early in the story of the search for life in that celestial field of millet, Mars became a target, a planet likely to bear fruit. It was always bright in the sky, always special, but as we began to see it through telescopes, Mars seemed ever closer to us and more like Earth.
The story of the search for life on Mars is largely the story of boys and men captivated by the possibility of not being alone. Sometime in the late 1830s, when Giovanni Schiaparelli was just a small boy, his life with space, and ultimately Mars, began. Late at night, he learned the constellations with his father, as falling stars lit the sky above him. He asked his father what the falling stars were. His father could not answer; no one could, and this inspired in Schiaparelli a “secret and confused feeling of immense and awesome things.” His imagination was already “stirred by thoughts of the vastness of space and time.”
Thirty years later, Schiaparelli was to show that the falling stars he had seen were meteors. He would for the first time in history link their fall to the orbits of comets. Schiaparelli would, in fact, go on to make many discoveries. In 1877, he was watching a double star through the telescope in the observatory of the Brera Palace in Italy, when he took a break to look at Mars. He had not intended to make long observations of Mars, but it captured his attention. Ambitious by nature, a week later he decided to undertake the most comprehensive study of the Martian surface ever conceived. He avoided coffee, alcohol, and “everything which could affect the nervous system,” in order to focus his senses on the job at hand. Sober, he mapped the planet, every nook and cranny, for years. He mapped until, in advanced age, he could no longer see well enough to work.
In 1877, the year Schiaparelli began, at the age of forty-two, watching Mars, Earth and Mars were as close as they get to each other, at thirty-five million miles.* When the Earth is nearest to Mars, Mars seems threefold larger to us than it does when the two are farthest from each other. In seeing Mars in 1877, Schiaparelli could see many features not yet detected by other astronomers. He named the features he saw, the envisioned seas and mountains, valleys and rifts. Through a telescope’s lens, Schiaparelli had become a kind of Columbus. He was not the first to see the new world, but he gave its features their lasting names.
Schiaparelli’s telescope was not quite good enough to see all of the forms he reported, but like Leeuwenhoek with his microbes, his imagination filled in some blanks. Filling in the blanks is what insight, visual or otherwise, sometimes depends upon. Schiaparelli did not, initially, speculate as to what the geological forms he saw on Mars were, but by convention he labeled the low areas “seas” and the high areas “lands.” Schiaparelli also labeled canali, the dark shapes that connected the mare on his map. Canali was a label that hardly seemed to need translation, but it did.
Canali might most directly be translated from Italian as “channels,” meaning physical forms created by the movement of water. However, one would have to agree that it does look like the English word “canal,” which implies forms created by sentient beings for the movement of water. Of the two possibilities, “Canals of Mars,” which implied canal builders, seemed far more exciting. In fuzzy images of other worlds, we see what we wish were true. In the lines on Mars, as depicted by Schiaparelli, we would imagine life.
Some scientists were inspired directly by Schiaparelli’s work. For others the news of the geography of Mars arrived indirectly, purveyed by writers who were very willing to add the details where Schiaparelli’s vision and drawing had left off. Many viewed Schiaparelli’s maps of Mars accompanied by the words of Flammarion, who offered a theory for the Martian canals. Flammarion suggested there had been civilizations that built the canals. The civilizations were far more advanced than our own. “They could,” he would later say to a New York Times reporter, “hardly be less intelligent than we are.”2
One of those captivated by the canals, as drawn by Schiaparelli and interpreted by Flammarion, was a young man named Percival Lowell. Lowell was working in Japan and Asia in 1877 when Schiaparelli first observed Mars. He was not yet a scientist. He was a well-educated and wealthy diplomat, known for his studies of Asian culture and his photographs of Asia, particularly Korea. After an extended stay in Asia he returned home to Boston to organize the publication of his book Occult Japan on the, to him, alien cultures of Japan.
While back in Boston, Lowell read Camille Flammarion’s La Planète Mars et ses Conditions d’Habitabilité. Flammarion offered descriptions of nearly all of the “scientific” observations of Mars to date, including those by Schiaparelli, along with his own interpretation of their significance. Lowell was captivated by Flammarion’s book. He was struck by the descriptions of Mars, the drawings of the sun rising over Martian canals, and the idea of civilizations on Mars, a land more distant and exotic than even Japan.
A book can change a person and Flammarion’s book appears to have touched some deep chord in Lowell. He had spent much of his life studying other cultures, and thrived on the necessary study and travel. Here in his hands was the possibility of cultures on other planets. He was called. He scrawled “Hurry” in the margins and got to work.
The next time Mars was in opposition to the Earth would be in 1894. Lowell would have to build an observatory, quickly. He had been interested in astronomy since he was a boy, but now he had to be an expert. It is hard to think of his new interest as anything but a kind of madness. But Lowell had enough money to turn his madness into success. At the address to the Boston Scientific Society on May 22, 1894, he announced, “This may be put popularly as an investigation into the condition of life on other worlds…. there is strong reason to believe that we are on the eve of pretty definite discovery in the matter,” and so began the quest that would occupy the rest of his life.
Lowell contracted astronomers immediately to help him choose a site for two telescopes.3 The astronomers chose a spot near Flagstaff, Arizona, where visibility would be good. Lowell would need a clear place to look if he were to see what no one had seen before. He was already convinced that intelligent life lived on Mars. What was left was to see more, to resolve details. He would study Mars through his lens the way that an archaeologist would study ruins, though it might be worth noting that archaeology would be very hard to do from tens of millions of miles away.
So much of science is about vision, about looking in new ways. Our senses did not evolve for understanding the stars. They evolved for choosing the right fruit, scavenging dead animals, and detecting danger on the horizon. Our horizons have changed, but our bodies remain the same. Our eyes are poor, limited in what they can lay hold of. They were meant to aid our survival, not to search for distant worlds. To use our eyes as tools for exploring space is like using a hammer to put in a screw. Hit it hard enough and it will go, but inelegantly. We have discovered, by using our quick minds, how to extend our senses—to make our hammers more like screwdrivers. Leeuwenhoek discovered his new world through the magnification of his lenses. Woese used rRNA to see features that were invisible even with a microscope. Lowell hoped that through his telescopes he would look up and be the first to see extraterrestrial life. The history of science seemed to be the wind at his back. Look through a big enough, good enough lens and you will see what no one else has seen, see what has always been there but just out of view. Lowell was ready to see Martians.
During the most favorable viewing time for Mars (May 1894 through April 1895), Lowell would spend every day—nearly every hour—looking, documenting, drawing, and mapping. His would be, he surely imagined, a map of Mars complete with cities and civility. Once he was convinced that Mars was inhabited, it is easy to imagine why and how he might become obsessed. It is, in some ways, harder to imagine how anyone could have avoided obsession. When Columbus began, he had only heard rumors of what was beyond the horizon. Lowell saw, in the hopeful lines of sketches, what awaited his ship.
On the first day that Mars was close enough to see well, Lowell had looked through his telescope and seen the canals. He would check again and again, day after day, but he would nearly always see the canals. Here was where dirt had been moved by intelligent life. The lines were too straight, the forms too perfect. Once he had seen the canals, he could think of nothing else.
There were other signs as well. Lowell did calculations and concluded that Mars had a reasonable climate, average 9°C, not the sort of thing for long swims in the Martian seas, but reasonable all the same. He saw clouds that would have buffered temperatures and he again and again saw the canals, which to him, and soon to an excitable public, seemed like sure evidence that intelligent beings had shifted water around the dry planet.
Lowell had understood Japan through comparisons to his own culture. He would now understand the culture and lives of the Martians through analogy to human life. Because of his travels, Lowell was as prepared as anyone to make the necessary extrapolation. To Lowell the canals looked to be the effort of a desperate civilization, hungry for water for their dying crops. The Martians used the canals to farm. The changing colors of Mars through the year were the phases of the Martian crops, the leaf on and leaf off. As Mars’s shadows turned dark, the Martians turned to their stored food and waited for rain. Here was a species in which we could recognize our deepest yearnings, both literal hunger and the more existential hunger to not be alone. For Lowell, the canal lines were “enough to put to rest all the theories of purely natural causation that have so far been advanced to account for them.” Out of lines, he imagined an entire world.
Lowell would defend his new visions for Mars for only a short while. The rush to build the telescopes and then the tedium of his daily observations had left him physically and emotionally drained. He was diagnosed with severe nervous exhaustion and would not return to work for four years. When he did return, he would realize that during the intervening four years the scientific community had attacked and belittled his work. The general public, though, had taken a more supportive view. They believed.
For a time, our understanding of Martian life rested nearly entirely on a debate over what Lowell could see through the lens of a telescope. He had drawn what he had seen, but as Carl Sagan would later point out, Lowell was “one of the worst draftsmen who ever sat down at the telescope,” such that his drawings on their own would never be convincing. The debate recalled Leeuwenhoek’s earlier problems with the Royal Society. Lowell said he could see canals. Others looked through similar telescopes and saw nothing, or indistinct blurs. By the late 1880s, Schiaparelli, whose work had initially excited Lowell, thought that the canals were natural, not made by life. Were Lowell’s eyes better or had he imagined the lines altogether?
In some ways, it may have been inevitable that we would imagine a Mars somewhat like Earth. Copernicus, when he removed the Earth from its special place in the universe, implicitly suggested that there must be many similar places in the universe. If the Earth is not special, then it must be ordinary. Lowell and his antecedents argued that the same must hold for life. Once the Earth’s life was found to be ordinary, the lives on other planets had to be like ours. The beings might have more or fewer arms, more or fewer eyes, but they too would look out, wondering if they were alone.
Just as in the days before we discovered the New World, in the days before we went to space, anything still seemed possible. We could populate the planets with whatever creatures we desired and so, as we always do, we filled those unknown lands with things like us. In the sea, we had seen mermaids. In new continents, we had imagined giants and trolls. In space, we would see Martians living in forests and savannas, farming crops in rows.
It would be many years before the Martian canals could be ruled out entirely. Hope endured, even as other astronomers picked apart Lowell’s observations one by one, yet long after most scientists stopped believing in the possibility of intelligent life on Mars, the public’s faith persisted. Lowell had cast his greatest dreams and fears onto the planets in the same way that indigenous peoples had long populated their jungles with myth and legend. There was a time when no one could tell the men in small Amazonian communities that the Earth did not have many moons or that their forests were not filled with giant monkeys or talking jaguars.
When Lowell died he was considered a fool by at least some of his peers, but his quest for Martian life would live on for generations.* Among those inspired by Lowell’s quest, if not his canals, was a young boy named Carl.† From an early age, Carl was pointed to space. He would dream about life in space as he drifted through school. When he arrived in college he would greedily take classes about space and biology. He was not the smartest kid in his classes, but he was among the most intense and passionate. He looked at the stars and, knowing they were each a distant sun, felt deep pleasure. If there was not life on Mars, there would be, he almost knew, life on a planet circling one of those more distant stars.
When he was a nineteen-year-old physics student, Carl met a girl on the stairs of Eckhart Hall at the University of Chicago.4 She was Lynn Alexander, just sixteen. They talked. They walked and kissed. Who can say exactly what drew them to each other? Neither was yet famous. They were, at least in their moments of young lust, ordinary college students.
To Lynn Alexander, Carl was “tall [and] handsome, with a shock of brown-black hair,” and was full of the kind of ideas that are sexy in college—big, exciting ideas about the world, both ours and those beyond.5 He was eager the way a bud is eager. He did not always listen, but if you were to listen, as Lynn Alexander listened, he would talk. What he talked about was life in space. If he was looking up, he was always looking beyond the clouds.
You have already met Lynn Alexander. She was to become, through the twists and turns of life and marriage, Lynn Margulis. Carl was Carl Sagan. He would go on to become perhaps the best-known scientist of the century. The young Margulis did not care about Mars or about the quest for life in space. She would tell a young Sagan “there’s nothing to be said about it because you don’t have any data one way or another.”6 She was, at best, agnostic on the question of life in space. She liked the more Earthbound possibilities, Carl Sagan included. He was, for his part, not yet famous but he already had presence. They would influence each other the way two spinning tops will touch and then move in new directions.* He would help to urge her into biology, into what would become genetics and her sweeping vision for endosymbiosis. He would later, in part through the influence of Margulis, become more deeply interested in the microbiological aspects of the story of life in space. Any of us would recognize in this young couple the intensity of young love, but their personalities already seemed to foreshadow something more significant.
Things would happen quickly for these young lovers. Sagan finished his master’s degree and asked the woman then known as Lynn Alexander to marry him. She made a tape recording of all the reasons she should say no, but eventually acquiesced. The list of reasons to marry him was not necessarily longer than its opposing list, but love is not science.7 In June 1957 they were married. Much was about to change, both for these two and for the world in general.
The next years would be a blur of children, science, and movement from house to house and city to city. Margulis went to the University of Wisconsin for her master’s degree. Sagan began his doctorate at the University of Chicago’s graduate astronomy program at Yerkes Observatory in Williams Bay, Wisconsin. Margulis would, by the time she finished her master’s, give birth to a boy, Dorion, and then become pregnant again with their second boy, Jeremy. The overlap between children, degrees, and discoveries is sufficiently complex as to make one question the dates. Somehow though, between diapers, formula, and sleepless nights, science was accomplished and the next stage began. They all went to Berkeley, where Margulis began her doctorate and Sagan began a postdoctoral position. She was beginning to be known for her outrageous ideas and he was already known for, among other things, thinking grandly.
Carl Sagan’s science was to include every possible aspect of astrobiology, the study of life in space. He would study the origin of life in the lab (picture an experimental bubbling stew with a scientist standing over it, wide-eyed). He would study Venus’s atmosphere and make predictions as to its composition. He would later listen for radio signals from beyond our universe, help to send probes to Mars and beyond, and more generally search the dark reaches of space for life. He was not the keen observer of science, not Swammerdam dissecting the oviduct, Leeuwenhoek with his tiny creatures, or even Margulis looking inside cells. He was more the visionary than the observer. He wanted to pull the whole picture together, to understand space and life in space. Lowell had obsessively tried to see space through a glass lens in the desert. Sagan wanted to see, too, and he also wanted more. The red planet in particular was so close and yet so far. Its possibilities were tantalizing, and like Tantalus himself, Sagan would spend his life reaching for life on Mars. The planet would remain, until the year of his death, just out of reach.
By 1960, when Sagan was working as a postdoctoral fellow at the University of California, Berkeley, Lowell’s vision of Mars was dead, but how scientists felt about the idea of intelligent life in space more generally was less clear. That our handful of nearby planets had no great civilizations seemed to have little bearing on the broader question. Sagan thought intelligent life common in the universe, but how many serious scientists shared his belief? He wasn’t yet sure, but he would soon meet a few, among them Frank Drake, with whom his quest for intelligent life in the universe would find company.
When the two met in the 1960s, Drake had already achieved various kinds of success. He had come as close as anyone to contact with intelligent life from other planets. In the late 1950s, he was working on a radio telescope at the Agassiz Station of the Harvard College Observatory in Massachusetts. A radio telescope is, in its most common design, a dish-shaped antenna used to detect electromagnetic radiation from sources in space. Today, a computer analyzes the signals the antenna receives, and a user points the antenna at the regions of space that seem potentially interesting. Humans then parse the results, interpreting the numbers in the way one might scan an image looking for canals. Drake had come to the conclusion that radio waves might be the most obvious signal other civilizations would send out into space. Other scientists, Giuseppe Cocconi and Philip Morrison, had simultaneously come to the same conclusion.8 It seemed that the ideas of contact (or the radio waves anyway) were in the air.
While manning the radio telescope at the Agassiz Station, Drake detected a mysterious signal from the Pleiades star cluster. He was a young man of twenty-six. He had, he imagined at that moment, just detected the first signal from intelligent life in space. It is impossible to overemphasize the enthusiasm, the raw possibility Drake experienced. In his autobiography, Drake writes “What I felt was not a normal emotion. It was probably the sensation people have when they see what to them is a miracle: You know that the world is going to be quite a different place—and you are the only one who knows.”9
If it had been a signal from a planet circling that star, and if Drake moved the radio telescope to one side, even a tiny bit, the signal should have disappeared. Drake moved the radio telescope off the star. He waited.
To Drake’s dismay, the signal did not disappear. It was not a transmission from intelligent life in space. It was something else, simply noise, but the moment was defining for him. He realized the possibility of what could be detected were we to spend more time listening. He felt he had been close to knowing what it was like to discover a signal from another civilization. The moment had marked him and he sat down, “sweating and shaking from the heady moments spent almost believing [he had] been in touch with a distant and alien mind.”
Although Drake had not heard the signal of alien life, he decided then that he would spend the rest of his life, if necessary, listening and waiting. If he were to be considered legitimate, though, he needed support. In 1961, by then working for the National Radio Astronomy Observatory, he got the support of his new boss, director Lloyd Berkner. It would not take long until Drake was again excited by a signal, this time from Epsilon Eridani, the third-closest star to Earth visible with the naked eye. He heard what seemed to be cyclical pulses, a kind of drumming. A “moderate amount of pandemonium” ensued.
Unfortunately, the signal had come not from Epsilon Eridani, but from a secret military project. There would be more setbacks, but the excitement of those moments of near discovery was enough to keep Drake, and soon others, manning the radio telescopes. In 1961, Drake organized the first conference on the Search for Extraterrestrial Intelligence (SETI) at the observatory in Green Bank, West Virginia. Carl Sagan was invited, as were a suite of other eminent and interesting scientists. Sagan, having just finished his doctorate, was the youngest scientist present. He was also perhaps the most outspoken member of the group, despite the caliber of the other attendees, among whom was Melvin Calvin. Calvin would be notified during the conference that he had won the Nobel Prize for work on the chemistry of photosynthesis. These were not humble beginnings.
A key question at the meeting was: how probable is the detection of intelligent life elsewhere in the universe? Even if the universe were full of life, it was not obvious that we would ever detect the signals. The group needed a better estimate of how probable detection was, something they could take to funding agencies, something that would make this endeavor something more than just a collection of geniuses waiting to win a lottery.
Drake had an idea of how one might estimate, however crudely, the lottery’s odds. He wrote a simple equation on the board. He couldn’t have known then that it was the equation that would define his career. It was a calculation of (N), the number of civilizations in the Milky Way Galaxy able and willing to engage in interstellar communication. How many chatty aliens were out there? Drake’s equation made clear that the solving of N depended on just a few things. First, life was more probable in the Milky Way if there were more planets.* One next needed to know the proportion of planets capable of maintaining life. The calculations now grew trickier. Drake made an estimate, but he was guessing. We have little on which we can estimate the probability that life will evolve somewhere. We know of only one place where life has begun, and therefore we can see life only through the lens of that origin.
The hardest parts of the equation to estimate involve evolution and its persistence and direction. For life from another planet to contact us, it must first evolve. We don’t know how often life evolves, except to say that it evolved once (and, so far as we know, only once) on Earth. Intelligent life must, then, evolve from unintelligent life. We know this to have happened one time, as well.* Once intelligent life evolves, it must then decide to try to communicate and it must try to do so during the narrow time interval during which we are looking.
The first part of the equation, the number of planets and the number of habitable planets, is possible to study empirically. The more it has been studied, the more probable life on other planets has seemed. The second part of the equation was always the more difficult part. We can only speculate as to what the estimates should be of things like the number of times life evolves. Some speculate stingily, others, Drake and Sagan included, cast about with more hope.
At the conference in Green Bank, the attendees debated the estimates for each term in the equation. Drake’s own estimates of the number of planets with intelligent life in the Milky Way ranged from one (just us) to one million, depending on each of the parameters in the equation. Each attendee probably went home with his own estimate of the probability of contact, but what was clear, at least to those present, was that the quest was not unreasonable. The probability of intelligent life seemed high enough, given realistic parameters, that Drake kept and keeps looking. It would, Drake, Sagan, and others would argue, be unfortunate to wait a hundred years to realize that we were being signaled loudly from the side of the galaxy’s road.
There were so many independent parts of Drake’s equation that were hard to estimate that it became easy for supporters and detractors of the idea of life in space to bend the equation, intentionally or not, to their preconceived notions of what might be found. Sagan saw in Drake’s equations hope and possibility, and he convinced the broader public of as much. He would talk daily about these probabilities, attracting attention, research money, and big projects. Drake spent the time searching the skies; Sagan spent the time asking questions and ultimately, as important as anything else he would do, garnering support. To many, intelligent life in space began to seem likely. It began to seem as though contact were inevitable, and if not contact, at least some sign.
The Green Bank meeting will be remembered for making the quest for intelligent life in the universe a serious endeavor. It would lead to advocacy on several fronts for large projects to detect life in space. Sagan in particular was able to use the meeting as leverage again and again as he advocated for more telescopes and landers, more eyes to the skies. Support was to grow. By 1982, Sagan published a petition in the journal Science, signed by seventy scientists, seven Nobel winners among them, advocating more funding for the search for intelligent life. By that time, there were projects all over the world in which scientists trained radio telescopes into the sky, listening for signals. In the old lingo of CB radios, because of Drake, Sagan, and others at the Green Bank meeting, we have our ears on. But so far the universe, big mama, has been quiet.
While Drake worked to use radio telescopes to listen for signals from space, a task he would continue on bigger and bigger scales, Sagan wanted to send missions to space. He wanted to make contact.
The big quest, this time, was to go to Mars. It was not only close and relatively less hostile than the other planets. It had also been the planet Sagan had, like many, dreamed about since he was young, since he had read Lowell and Edgar Rice Burroughs the way Lowell had read Flammarion, enraptured. He dreamed Lowell’s dream. In the late 1960s, Carl Sagan seemed on the edge of realizing his dream. He was involved with the Mariner 4 project to send a probe to do a flyby of Mars.
Mariner 4’s predecessors did not inspire a great deal of hope. Mariner 1 failed during launch, crashing and burning on the launch pad. Mariner 2, an exact replica of Mariner 1, showed Venus to have cool clouds and a hot surface. Venus was warm, as Sagan had predicted earlier, but at 800°K, far too warm for any known life. But Mars was and had always been the big hope. Mars was where no one wanted to fail. Mariner 3 was intended for Mars, but died before it reached its destination. Mariner 4 would, if it were successful, be the first real view of Mars. The probe went up with Carl Sagan’s dreams tied directly to the images it might bring back. He still imagined a Martian planet lush with life.
On July 14, 1965, twenty-one photos came back. The images showed a barren and lifeless landscape. Newspapers announced that we were alone. But Sagan would not give up easily on intelligent life. Like Quixote before the windmills, Sagan was not to be dissuaded. He offered that “Had the Mariner 4 vehicle passed the same distance from the Earth that it did from Mars (6000 miles) and obtained 22 comparable photographs, no sign of life on our planet would have been uncovered.”10
When he finally did begin to have doubts about Mars, Sagan simply cast his hopes for intelligent life outside our solar system. Sagan helped launch the Voyager probes. The probes were to drift through time, further and further from Earth, bearing a note, a kind of skywriting for deep space. Sagan was instrumental in designing the message, which included a variety of symbols meant to be universal (though relatively hard to decode, at least by the intelligent lives on Earth who tried). In addition, there was a picture. It was of a man and a woman standing naked side by side. They were not holding hands or touching. It is hard to imagine how we might have more demonstrably painted our longing onto that ship, more clearly announced our desire to not be alone.
After Mariner 4, Sagan did not give up on Mars, but he would shift to talking about smaller life. He became a proponent of the idea that microbial life would be found there. He predicted it would happen soon. Here was an aspect of his interactions with Margulis surfacing. If she had imagined any life in space at all, she would have imagined microbes, perhaps even symbiotic ones. Now Carl Sagan would imagine them too.
Eventually there would be rovers that patrolled the Martian surface, but even before then the hopes of man-beasts in the Martian light had vanished. For those who grew up imagining vast cities on Mars, the idea of any life there other than intelligent life seemed like a let-down. For Sagan though, microbes would be life and if there were life nearby, there might be life far away, there might be life everywhere. While Frank Drake went on listening for signals, for wild calls in the dark, the new race was to find life, any life, on our nearby planets. For many astrobiologists, that there is life somewhere else in the universe seems a near guarantee. Statements about the self-evidence of widespread life in the universe are easy to find, written by fool and Nobel Laureate alike. But just as conspicuous as statements about the high probability of life was the lack of data. That was soon to change.