* * *
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WHEN SUMMER TURNED to fall, I finally returned to Boston. I watched the skyline come into focus as the plane neared Logan Airport, all the tiny buildings. After landing, I walked out of the terminal and found a taxi. “No luggage?” the driver asked.
As we sped along Storrow Drive, I rested my head against the window, watching the sailboats bob in the river. When the taxi dropped me in front of my apartment, just off Beacon Street, it looked the same as it always had. I walked up the two flights of stairs and let myself in. There in my bedroom, on the windowsill, I noticed the mug of tea I’d made for myself the morning before I left. I’d forgotten it there, and it was as if it’d been fossilized. The liquid had vanished, and when I lifted the thread, the featherweight tea bag detached effortlessly from the ceramic. I stared at it for a long time, wondering what it said about me that I could step out of my life so easily, and what it would mean to step back in.
OUT IN SIBERIA, the Kolyma Lowland stretches across the far eastern steppe. The gray sky hovers close to the sediments, breeze-blown silts cemented by massive amounts of frozen water. Great fists of land are upturned into hummocks by expanding and contracting ice. The Kolyma Highway ebbs through it, the “Road of Bones,” named after the thousands of gulag prisoners who died constructing it. Human skulls were once so common that children used them to gather blueberries.
In the 1990s, shivering scientists had begun to drill cores along a twelve-hundred-meter stretch between the Lena and Kolyma rivers. Deep below the thawing surface, they accessed places where the temperatures never warmed, where there were no water-bearing horizons, where thick ice veins had persisted intact for a million years or more. They were careful to control for contamination—their own human cells, the microbes that lined their tools, even windblown bacteria. They slowly, painstakingly, rotated a corer to avoid using drilling fluid—twenty, thirty meters deep. They painted the cores with cells of Serratia marcescens as a marker for contamination. Then they carved away the outermost surface with sterile scalpels and sealed the pared-down batons of frozen earth within the sterile metal cases of a borehole freezer, hauled out to the middle of nowhere.
Dice-sized cubes of those cores eventually made their way to laboratories in Oxford and Copenhagen, where some of the best ancient DNA research in the world was being conducted. They were carefully peeled open, tiny rootlets snapping as they were exposed to the air—the ancient roots of ancient plants, still gripping grains of soil. Within those same frozen lumps of permafrost, the DNA of woolly mammoths, lemmings, and reindeer was uncovered, as well as spores, pollen, and the traces of ancient microbes—all perfectly preserved. These were the remains of an ice-age ecosystem, one that had been lost to the world.
After leaving JPL, I’d read about the study, transfixed by the exquisite resolution of data, the resilience of those delicate molecular fingerprints. In particular, I thought about the microbes. What happened when life was pushed to its very limits? How long had they survived in the subsurface? If life could persist underneath former western Beringia, I reasoned, perhaps life could persist on Mars too. I knew there was other water on Mars—frozen water, swaths of it laced underground. Not just at the poles but all the way down to the low latitudes, and it had been there for millions of years. To many people, the most exciting thing about that discovery—made in 2001 by a NASA orbiter—was that human explorers might one day mine that water: thawing the ice, baking it from hydrated minerals, using it as a resource in colonization. But I couldn’t stop thinking about whether life could be embedded deep in that frozen ground, beyond the reach of the acidic waters.
* * *
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IT WAS ONLY a few months later, in the dead of winter, that I found myself at the Niels Bohr Institute in Denmark. I’d proposed to Maria that some time in Europe would expose me to cutting-edge biology, and she gamely agreed to another prolonged leave from campus. When I arrived in Copenhagen, I moved into a pocket of a room on the ground floor of a laboratory building. There was just a chair, bed, desk, and window looking out onto an empty greenhouse. It reminded me of the miniature dioramas I’d made inside shoeboxes as a child.
I was in a country of strangers, and everything seemed quiet. Parents left their babies in carriages outside store windows, their sleeping bodies bundled against the cold, their faces tucked below a billowy sleeve of fabric. Danish cars glided through the Danish snow. Sun glinted off iced-over bicycles. Even the restaurants and coffee shops, with their white walls and beautiful dishware, seemed hushed.
I’d come to Denmark to learn about ancient cells and ancient DNA, to see if cells could persist in ancient permafrost, in some of the most challenging conditions on Earth, to help figure out whether the microbial DNA recovered in those Siberian cores was DNA from living cells—potentially, possibly, surviving over ancient timescales—or simply the remains of creatures long dead, like the woolly mammoth.
I had the chance to work with one of the pioneers in the field, Eske Willerslev, as he was setting up his newly formed group. I’d met him during his research fellowship at Oxford, where I’d also spent time studying. You wouldn’t guess it from his chain-smoking or the black-and-white-checked Vans on his feet, but he had once disappeared into the wilderness for nearly four years, living part of the time as a fur trapper. He survived off moose meat as he and his twin brother canoed up untamed rivers and explored the frontier tundra. He was a brilliant scientist but also a bit of a nomad. Like me, it seemed, he traveled light.
Most days, I alternated between two labs, one in the building where I was living, and the other in an older structure across the way. The labs had been separated to isolate the cleanroom. Contamination was such a pervasive issue that the cleanroom had not only been built in a different building but also secured behind a pressurized antechamber. If there was life at all in that permafrost, we knew there wouldn’t be much, and we had to be very careful. I never entered if I hadn’t showered just before and changed into freshly laundered clothes. Inside, I worked in double gloves, sterile sleeves, a puffy Tyvek bodysuit, and a face mask. Crossing into it felt like crossing a threshold into a spaceship.
I liked my newfound proximity to the lab bench, accessible at any hour, any day. I found solace in the supreme isolation, the quiet. I hardly ever left the lab, but when I did, it was to drift through the city. I once wandered into a cemetery in the heart of Nørrebro, where the rows of headstones were desolate. Patches of snow clung to the epithet on Søren Kierkegaard’s grave: “In a little while, / I shall have won, / The entire battle / Will at once be done. / Then I may rest / In halls of roses / and unceasingly, / and unceasingly / speak with my Jesus.” I returned to my little room and spent the evening with an English copy of Fear and Trembling, listening to the whir of the generators.
After a few months of steady, constant effort, I started to see thrilling results: evidence of intact ancient cells. I’d been hoping the work would have implications for how we think about life detection, and it looked as if we’d discovered that tiny bacteria could survive over epic timescales: 300,000 years, 400,000 years, perhaps even 600,000 years.
Eske underscored the importance of proceeding cautiously. We arranged to transport a portion of the original samples to a lab in Australia, to ensure they could replicate what I was finding. But if those cells were indeed alive, how were they alive? How did they make it in a place so devoid of warmth or nutrients? How could they endure the ravages of time? I thought about it as I paced the city, as I ate granola in the mornings. Perhaps they shut down operations entirely, hunkering down and surviving in a state of dormancy? Or perhaps they found a way to repair the inevitable damage?
A couple of weeks later, we took the train to Lund, Sweden. In collaboration with colleagues there, we set up an experiment in small stainless-steel chambers. The cells would sit at subzero temperatures for nine months while tiny sensors attempted to measur
e minuscule puffs of gas as they “exhaled.” If the cells were in fact “breathing,” if those data aligned with our genomic results, then we would have a big discovery on our hands. It felt like a long time to wait, but of course it was just a heartbeat in the life of those cells.
In the weeks that followed, I continued to gather additional measurements. Within the building’s massive stone walls, I could feel the warmth of Denmark’s near-Arctic light as it fell through the windows onto my masked face and gloved hands, the heat of our enduring star. I rechecked all our positive and negative controls and ran some auxiliary experiments in the cleanroom. Late in the afternoons, as the sun began to set, I’d duck out for a tea break, pacing the halls holding my warm mug, thinking about how this place was home to some of the most remarkable contributions humans had ever made to science. The basic structure of the atom had emerged from those very rooms. Later, the Institute had borne witness to the transition from classical to quantum mechanics, to the world veering from deterministic to forever probabilistic. It was home to a vibrant intellectual history, housing its memories within sturdy walls—walls that were full of fossils, the calcified husks of lives long gone. I was there for only a moment, but in that moment I was staring into the ice age, and I was surrounded by things that were built to endure.
While I was waiting for the Swedish results, I moved back to Boston and into a new apartment. I passed my generals—the qualifying exams for my PhD—and began the intimidating work of outlining my dissertation. I also worked on the DNA paper, and each time I did, it was like taking a break from my future to look back in time. I’d think about it as I jogged through Mount Auburn Cemetery and rode on the rumbling subway beneath the city. I wondered if the cells in those tiny incubation chambers were still alive, releasing tiny whiffs of gas into the stainless-steel tubes. I worried our apparatus might not be sensitive enough to see them.
* * *
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WHEN THE RESULTS came in—confirming at long last that the microbes were alive, barely but clearly respiring—I nearly burst with excitement, rushing to Maria’s office to share the news. I spent the next couple of months writing up the paper. After it was submitted, there was more waiting—for the reviews to come back, then for the editors to respond to our responses. The weeks and months passed. I’d fallen into a rhythm, working as steadily as the scullers who rowed along the Charles below my office window. Before I knew it, it had been more than two years since I’d returned to Cambridge. The migrating geese had come and gone—north in the spring, south in the fall. The tree branches had held the weight of snow through the winter and then grown anew.
One crisp autumn evening on my way back from the lab, I stopped by a bar in Harvard Square. A gathering of alums from a fellowship I’d received as an undergraduate was under way, and I’d promised a friend I’d stop by. I was wearing a backpack over my coat, the kind of thing you could only get away with in a college town. As I lifted an appetizer from a tray, a charismatic guy at the center of the room caught my attention. I noticed that his “HELLO” name tag listed the same class year as me, and he was talking to others I knew. It was puzzling. I didn’t recognize him, but it seemed impossible that I would have forgotten someone in my cohort. When I walked over to inquire, he laughed at my cross-examination. He’d just stopped by with a friend, who instructed him to scribble something to get a free drink. He glanced down at my shoulders and smiled at the backpack. I let it slide off my back as we talked for a few minutes.
He’d grown up in Boulder, Colorado, he told me. He’d started off in philosophy but was now studying to become a public-interest lawyer. I mentioned some of my work on Mars and life in the permafrost. I told him proudly about my new paper—my first as the “first author”—which was just going to press. I told him that I had demonstrated how a leading theory for cell survival—dormancy—came up short. Rather, the oldest cells displayed an amazing ability to slow down cellular activity and repair their genomes. They didn’t succumb, I said; they recovered, slowly but surely fixing the damage that had been done.
Before I walked into the cold that evening, I looked back at him, and he looked at me and smiled. Then the wind blew the door closed behind me, and I headed home through the fallen leaves.
* * *
—
THE QUESTION OF survival was a live one on Mars too. Might evidence of an ancient ecosystem linger there? Might ice in the polar Martian soil potentially become unfrozen and available to microbial cells? Might life persist between thaws? Whether extinct or extant, it stood to reason that ice and subsurface permafrost would be an ideal place to search for evidence of life. Eske’s work had also caught the attention of a Mars scientist named Peter Smith, whose thoughts careened toward Mars when he realized that the entire phylogenetic tree of life had been reconstructed from those samples from the Kolyma lowlands, the very same samples I had worked with.
Smith was born the same year as my father and had the same shock of white hair. Not long after ringing in the new millennium, he decided to propose a mission that would land on Martian polar terrain to assess its biological potential. He envisioned the mission, which he named Phoenix, rising from the ashes, like the mythical Arabian bird, recouping the lost science from Mars Polar Lander. The spacecraft would be cobbled together from spare parts, with recycled hardware and software, on just a shoestring budget. To Smith’s delight, it was selected as NASA’s very first Scout mission, a cheaper supplement to the core missions of NASA’s Mars Exploration Program.
Phoenix was a precarious concept right from the start. It would become the first Mars mission ever to be run and operated out of a university—the University of Arizona—rather than a NASA center. Pulse thrusters were going to be used for landing, not the inflatable airbags that had safely cocooned Pathfinder and the Spirit and Opportunity rovers. And somehow it was going to operate on the polar terrain, whereas almost all the successful missions to Mars had touched down within a relatively tight band around the equator. The limitation on solar energy would place severe constraints on the amount of power available for the instruments.
Smith suggested landing on the northern polar plains, a Mars latitude similar to that of Canada’s Northwest Territories, not the doomed southern polar plains, where Mars Polar Lander had crashed. It was too dangerous to land on the pole itself, on solid ice—but at least the low elevation of the northern half of Mars would mean the spacecraft would have more atmosphere to slow it down, making for a safer landing. The targeted area in Vastitas Borealis was one of the cold, mysterious places that had just been identified by the Mars Odyssey mission as having extremely high amounts of water ice in the permafrost just beneath the surface.
In the spring of 2008, as the Phoenix lander approached Mars, a couple of hundred scientists and engineers filled two operations buildings on the outskirts of Tucson. The structures were single-story and had been dirt-brown until the University of Arizona’s art students painted a fiery mural on the south wall. Meanwhile, Smith left for Pasadena to prepare for the press conference at JPL. He’d been told over and over to expect the mission to fail, so when he arrived, he stood in the von Kármán auditorium, at the same podium as all his predecessors who had led Mars missions, rehearsing a press conference revealing that the mission had crashed into the surface. The press office prepared press releases for a half dozen doomed scenarios, such as the parachute failing to open. The days unfolded one by one, with tension presumably similar to what he’d felt as a child when his virologist father became one of the first people to ever receive the vaccine for yellow fever (it was self-administered). “Well, Dad, how are you feeling today?” Smith had asked him, day after day.
The landing was scheduled for Memorial Day weekend. On a whim, the media team at JPL decided to set up a Twitter account. They reasoned that a feed would allow NASA junkies to follow the events with their cellphones. Twitter was relatively new, and at first it wasn’t obvious that
anyone would sign up. Veronica McGregor, JPL’s media-relations manager, elected to have an email sent to her with every new subscriber. She also realized with her first tweet that using “I” instead of “the spacecraft” or “Mars Phoenix” would help her stay within the 140-character limit. It was a small adjustment, largely inadvertent, but it humanized the little lander. As Memorial Day neared, and the spacecraft’s plucky new account got mentioned in an online Wired article, McGregor’s computer started dinging like “a Vegas slot machine.”
When the landing day came, a high-resolution camera on the Mars Reconnaissance Orbiter captured a remarkable photograph of Phoenix plummeting toward the pole. The parachute opened a full six and a half seconds later than expected. It pushed Phoenix to the very edge of its landing ellipse, yet the retro rockets fired flawlessly, placing the spacecraft down perfectly level, in front of a giant crater. The lander did a pirouette as it opened, aligning its solar panels in an east-west direction to maximize the light hitting them. @MarsPhoenix tweeted, “Cheers! Tears!! I’m here!”
* * *
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THERE WERE MULTIPLE cameras on Phoenix, the smallest able to resolve the surface structure of a grain of sand, and when they flipped on, the vista was incredible. The polar terrain stretched without end and looked like one of my grandmother’s well-loved old quilts. The patchwork ground had been broken into intersecting polygons, some a couple of meters in size. It was a gorgeous worn geometry, formed by the repeated expansion and contraction of subsurface ice. The team knew that their size was determined by the distance from the ice table. Some crinkling of the surface—shallow knolls and dips—had been seen from orbit, but when Phoenix landed, they saw “polygons within polygons within polygons,” all formed under different climatic conditions. It meant the periglacial environment on Mars was complicated and remarkably active.
The Sirens of Mars Page 16
