Five Billion Years of Solitude (36 page)

The sky overhead was hazy when they reached the northernmost point of their journey. Even though they were more than 200 kilometers north of the tree line, smoke from the fire-ravaged southern forests still reached them on strange, unseasonal winds. Atop a treeless knoll, they stumbled upon five stone cairns. Old Inuit graves—the first sign of humans Seager and Wevrick had seen since Kasba. Scavengers or looters had scattered some of the rocks aside, revealing artifacts of rusted metal and wood, as well as a small sun-bleached human skull. Seager snapped a photograph. She wondered what the person had looked like, how they had died, and why they had chosen to live so far from the world she knew. She looked up from the skull to the surrounding hills, spotted with pale grass and summer wildflowers, rolling on and on. The silence was broken only by the whisper of wind rippling from horizon to horizon. Silver and blue circles of sky pooled in the clear, cold water of countless lakes. In that moment she understood why someone might abide in such everlasting solitude.

After crossing back south beneath the tree line, they entered what Seager called “Esker Territory,” a seemingly interminable warren of sandy pink hills coiled in complex double and triple ridge systems, with small lakes and woods lying in the valleys between. It was beautiful, but exhausting to cross. The days blurred, and the geography rolled by like even-spaced rumble strips on a lonely highway. All was esker. Then lake. Forest. Esker. Lake. Boulder-filled streambed, esker, and lake. They smoothly, silently paddled and portaged for hours, now adapted to the rhythm of the land long ago laid down in the ebb and flow of ancient ice. No words were needed. They were in unison, almost reading each other’s thoughts. On one of their last evenings in the far north, Seager stood alone atop a spruce-sheltered ridge, contemplating the blue lakes and pink eskers as the Sun sunk lower in the sky. They were in a different world, one made all the more real by its distance from the bright, baleful cities and ever-scurrying crowds. Perhaps someday the cities and crowds would encroach here, too, driven poleward by drowned coasts, but for now the land lay empty. They had seen no one
else for over a month, yet they were not lonely. They ate when hungry, slept when sleepy, and lived simply, yet never yearned for more. “We had grown so content with each other’s company that we had no psychological or emotional cravings for anything or anyone from ‘outside,’” she later wrote. “The trip became our perfect life.”

When their plane lifted off from the airstrip at Kasba on August 28, Seager looked down with wistful thoughts at the windswept lake and the little rivers that blindly meandered through the grasslands and conifer woods. “In sixty days, ‘real’ life had become so dim as to seem partly impossible and mostly unbearable,” she would recall. “The solitude, the vast wilderness, the free and compelling lifestyle, the constantly changing terrain, and my excellent companion were a truly unbeatable combination.” She realized she had not only fallen in love with remote desolation; she had fallen in love with Wevrick, too. Soon after they returned, Seager asked him to move with her to live together in Cambridge. Without hesitation he agreed.

•   •   •

A
t Harvard, Seager initially focused on cosmology, specifically the basic physics behind “recombination,” an event that occurred less than a million years after the Big Bang. Back then, our universe was still just a hot expanding mass of plasma, an opaque fog of electrons and protons with no atoms, no molecules, no stars and galaxies. For hundreds of thousands of years the plasma cooled and expanded, until it reached a critical transition, becoming cold enough for electrons to “recombine” with nuclei, glomming together to form atoms. In a literal flash, the atoms froze out of the primordial plasma, transforming the expanding fog of plasma into a transparent cloud of hydrogen and helium, unleashing a flood of light that still reverberates through the universe today. We detect it as an omnidirectional all-sky glow of microwave radiation with a temperature less than three degrees above absolute zero. As Seager worked on recombination, the first discoveries of hot Jupiters were
trickling in. She approached her advisor, Dimitar Sasselov, looking for ways to segue into exoplanets, which she saw as a more interesting topic. Sasselov steered her toward modeling hot-Jupiter atmospheres, since, as with the epoch of recombination, the associated calculations partially concerned the mechanics of high-temperature hydrogen and helium. From that seed sprang Seager’s subsequent PhD and her career-defining early work that led to the first detection of an exoplanet’s atmosphere.

Meanwhile, Wevrick forged a successful career of his own writing and editing high school science and math textbooks. Throughout Seager’s Harvard tenure they escaped the city for the countryside whenever they could, and they eventually married in 1998, the same year that Seager completed her PhD thesis. The following year they relocated to Princeton, New Jersey, where Seager had secured a five-year fellowship at the Institute for Advanced Study, the same establishment where Einstein had spent the last years of his life. There, with the encouragement of another mentor, the late astrophysicist John Bahcall, Seager began meeting with several exoplanet-oriented researchers at nearby Princeton University, developing concepts and techniques that could be used to characterize exoplanet atmospheres and surfaces with one of NASA’s forthcoming TPF telescopes.

After one such meeting, Princeton’s David Spergel was inspired to conceive the coronagraphic masks that became a technological pillar for TPF-C. After another, Seager and two Princeton astronomers, Eric Ford and Edwin Turner, devised an exquisite method to gain information about an Earth-like exoplanet solely from the fluctuating brightness of its pale blue dot as seen across interstellar distances. They began by developing a model to calculate the amount of scattered starlight any given planet could project toward a distant observer, and as a test case ran it based on Earth-observing satellite data. As our virtual pale blue dot turned in various viewing geometries beneath their model’s scrutiny, over time the team found they could discern what region of the planet they were looking at solely from its brightness, despite its reduction to an unresolved starlike point.

Looking down on the equator, for instance, each day like clockwork the relatively bright continents of North and South America would rotate into view, sandwiched on either side by long dark stretches of open Atlantic and Pacific Ocean. In their repetition, such patterns revealed the length of Earth’s days. With the rotation rate established, Seager, Ford, and Turner could attempt more granular mapping, trying to discern the bulk fraction of ocean versus land, as well as finer features such as forests, prairies, deserts, and ice sheets. They feared bright reflective clouds would confuse their observations, but they found that clouds tended to arise and dissipate in predictable ways—more often at land-sea interfaces and less frequently over open ocean and dry continental interiors. They learned to distinguish the reliably cloud-free Sahara Desert by the intense near-infrared brightness of its hot sand and the lush, verdant Amazon Basin by its constant blanket of clouds. They saw hints of ice sheets, lakes, and seas by occasional spikes in brightness, when their smooth, flat reflective surfaces glinted sunlight back into space like mirrors. Given enough time, they suspected, they could even discern the varying reflectances of shifting vegetation, clouds, and ice cover that would come through changes in weather, seasons, and climate. All purely from a single wavering point of light, without the need to first obtain planetary spectra using an 8- to-16-meter mirror in space. Of course, they had the advantage of already knowing what they were looking at; teasing apart such features for the unknown environment of an actual faraway terrestrial exoplanet would be much more difficult. But the technique offered hope that even a relatively small 2- to-4-meter space telescope might be able to roughly map any Earth-like planets around the handful of closest stars. Seager pressed on, churning out a series of papers outlining how extremely precise measurements of transits could reveal properties such as an exoplanet’s rotation and atmospheric structure.

Now midway through her fellowship, Seager began searching for what would come next. Despite her leadership in the rapidly growing field of exoplanets, she received polite dismissals from many potential
employers, who seemed to believe Seager’s optimistic visions of finding other Earth-like worlds would never come to pass. The exception proved to be the Carnegie Institution, which offered her a job in 2002. With Bahcall’s blessing, she left the Institute for Advanced Study and moved with Wevrick to Washington, DC. At Carnegie, she became even more involved with planning for NASA’s TPFs, and was for the first time exposed to the rigor of geophysics. Seager began exploring how to theoretically and observationally constrain not only an exoplanet’s surface and atmosphere but also its deep interior—things like its bulk composition, or its likelihood of volcanic activity and plate tectonics. Transits were key, since they allowed astronomers to measure a planet’s radius, its size. Paired with mass estimates from radial-velocity measurements, this yielded a planet’s density. Seager and others developed mass-radius relationships for worlds of various compositions, estimating how planet hunters could distinguish between, say, one Earth-size planet made of pure water and another composed of mostly carbon, or iron. The work would later prove crucial as more and more worlds of intermediate dimensions were detected. When they transited and their densities were calculated, many of the so-called super-Earths astronomers were finding proved in fact to be “mini-Neptunes,” gassy worlds with thick, opaque atmospheres of hydrogen and steam, rather than rocky planets with thin layers of translucent air.

As an emerging leader in the burgeoning field of exoplanetology, Seager began receiving frequent invitations to speak at high-profile conferences, meetings, and colloquia, and her retreats to the wilderness with Wevrick grew few and far between. In 2003, the trips for work and play were both sharply reduced—Seager became pregnant, and gave birth to their first child, a boy. They named him Max. Another boy, Alex, followed two years later.

By the autumn of 2006, though the field’s fortunes had fallen when NASA pulled the plug on TPF, Seager’s star was continuing its rise. MIT had lured her from Carnegie with an offer of immediate full tenured professorship—the equivalent of a lifelong golden ticket for
any academic, but one particularly valuable for a researcher so young and just starting a family. Seager and Wevrick placed a mortgage on a grand old house in Concord, Massachusetts, a fixer-upper not too far from Walden Pond. She would begin her professorship in January of the New Year. Seager was pleased with her progress, and broke the news to her father on a visit back home. He had recently been diagnosed with terminal cancer, and though he was fighting hard, they both knew he was in rapid decline. Her gamble on astronomy had worked out, she said. She was thirty-five, already with tenure at one of the world’s premier institutions—she told him it was the best she could expect to do. Seager hoped he would be proud. Instead, he transfixed her with an icy stare and answered slowly, with a voice like cold steel, “I never want to hear you say that anything is the ‘best’ you can do,” he said. “I never want you to be limited by your own negative thinking. I know there’s an even better job, and I know you’ll get that one too, someday.” Not long after their talk, her father died. To the very end, he pushed Seager to never stop thinking big.

At MIT, she began thinking bigger than ever before, assembling several research groups and pursuing multiple different initiatives designed to extend her expertise from theory into observation, engineering, and project management. To have any hope of being at the helm of a future TPF, she would need experience in all four realms. Personally, professionally, her focus was fixed on the future—every day, it seemed, the boys grew, looking more and more to her eyes like their father. Wevrick taught Max and Alex how to paddle a canoe, bait a hook, and make a fire. Seager taught them, too. She would tell her wide-eyed boys about the origin of the Sun and the Moon, the history of the Earth and its companion planets, and the newly discovered worlds that circled so many stars like grains of sand. Max loved logic and numbers—perhaps he would become a mathematician. Alex enjoyed puzzles and games, and like his parents was drawn to the outdoors. Perhaps he would be an artist, an inventor, or a forester. By the time they were men, she thought, NASA could again be preparing for TPF. She would be
ready, having raised a family and acquired new skills in the interim. Her life, intertwined with Wevrick’s, was coming into fuller bloom than she could have ever hoped or planned.

In late September of 2009, Wevrick began to notice a dull pain and occasional sharp cramps in his lower abdomen. It seemed to flare up randomly—he could find no correlation between the pain and anything he did. At first he didn’t worry much—after all, he regularly exercised, ate healthy food, and didn’t smoke—but after weeks of discomfort he began consulting medical websites, yielding indeterminate results. By mid-November, the pain had grown worse, and he was worried enough to seek advice from friends. His friends suggested one malady after another: appendicitis, inflamed gallbladder, irritable bowel syndrome, ulcers, diverticulitis, a hernia, Crohn’s disease. None perfectly matched his symptoms, which were stubbornly general. Seager convinced him to see a doctor, who, after cursory poking and prodding, found no signs of serious illness. Over the next two months, he experienced a few bouts of pain and vomiting, which he assumed to be food poisoning. In mid-January of 2010, he suffered another attack, more severe than before, and ended up in the emergency room. A CAT scan, colonoscopy, and biopsy revealed grim news: a large mass of what appeared to be cancerous cells had blocked most of his small intestine. He’d had Crohn’s disease after all, asymptomatic and undiagnosed for years, but the chronic inflammation had finally sparked cancer.