McKay was so excited that he printed out the image and left it for his thirteen-year-old daughter to find. “What does that look like to you?” he asked her, trying to be casual, after she saw it. “Bacteria,” she replied candidly.
The images solidified McKay’s decision to publish the results. The carbonates, the magnetic minerals, and the PAHs appeared in every last sand-sized sample of the rock he and his team analyzed. All three features were suggestive of life. And those structures McKay had imaged could well be the visual remnants! There were other plausible explanations for each feature, but taken together, particularly in light of how they clustered in the same place, McKay concluded something astounding: that they had found the first ever evidence of primitive life on Mars.
He and his team carefully finished the manuscript and submitted it to Science, which lined up a slate of nine reviewers, including Carl Sagan, to weigh in on whether the article should be accepted for publication. In 1994, just two years earlier, Sagan had written an article himself noting that no microbes had been detected in rocks from the sky, at least not yet. He was dumbfounded when a copy of McKay’s manuscript landed on his desk. With ALH84001, it seemed that his life’s work had finally come to fruition, and just in time, as Sagan was battling bone marrow disease.
As soon as the paper was accepted, the journal scheduled a release date for the middle of August. Foreseeing the press frenzy, NASA went into lockdown, determined to keep the news under wraps until the paper’s official publication date. That left McKay about two weeks to catch his breath before he would become one of the most famous scientists in history.
He and his family set off on a camping trip along the Frio River. The state park where they set up was located on soft rock that had formed a hundred million years ago in the margins of shifting seas. It was a geological wonderland. Prehistoric animals had left their footprints in the sand, and a plateau of limestone pushed upward along a curving fault. They drove below the canopies of cypress trees, slowly winding their way over the Cretaceous rocks.
* * *
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LIKE MCKAY, I have always felt at home among rocks. When I was a child, my father loved dragging my sister and me out of the car to look at roadcuts, those sections of highway where the land had been sliced away to make room for the asphalt. There were roadcuts all along the Mountain Parkway, which is how we got from my house to my grandmother’s in eastern Kentucky. My father’s mother was a tough woman, and only got tougher as she aged. She stopped taking X-rays after my grandfather passed away, but she still gave porch perms, and she still made soup beans with rowdy irreverence in her dark, wood-paneled kitchen. My father would stop often along the way to search for fossils on those rock walls: the bryozoans and brachiopods, the roly-poly trilobites and ostracods, and the ancient crinoids, saltwater animals once attached by a stalk to the seafloor.
About halfway to Hazard, there is a stretch of parkway where the years skitter by in the tens of millions. The rocks there are stacked like pancakes, getting younger and younger with each passing kilometer. They chronicle the history of life as it climbed up onto the barren continents—as amphibians took hold, then insects, then sail-backed reptiles.
We’d be driving that road, my sister and I in the backseat of the car, when my father would open his thermos. We couldn’t stand the smell of coffee. We’d roll and moan in protest, gasping for air from the open windows. As we pretended to suffocate, my father would seize his chance.
It was often near Slade where he would veer our long gray Chevrolet over to the guardrail, where the parkway plunges down and back up an escarpment at the edge of the eastern Kentucky coal field. My mother would sigh patiently as he summoned us from the car for some fresh air and a geology lesson.
I would have been embarrassed if my friends had been with me, but they weren’t. So, like a good student, I’d take my sister’s hand and tromp over to where my father was waiting. He would point out the layers in the rock, how they’d dip and twist and disappear. My sister, Emily, would nod. She was two years older, but because she had Down syndrome, I had caught up to her in height by the time I was seven or eight. She would smile up at my father with her sweet almond eyes, tracing the junctions with her finger. Meanwhile, I’d be crouching down on my knees, hunting the rock for fossils.
I was too self-conscious to admit it, but I found it fascinating that the ground held secrets, that life had been mummified into rock. The scale of it was tremendous. The formations stretched for kilometers, recording what it was like before birds flew through the air, before flowers adorned the world with color. When the seas were shallow, when Kentucky sat on the equator.
When I first saw ALH84001, I couldn’t help but think of the crinoids preserved in the roadcuts back home. For the longest time I had thought those crinoids were crawling creatures, for they looked just like the ringed earthworms that would splay themselves across our sidewalk after a heavy rain. And I was accustomed to seeing sinuous shapes in the soft siltstones, blending in with the texture and color of the surrounding rock. Those impressions were trails in the mud left by worms, but they weren’t left by crinoids. Crinoids didn’t have serpentine, soft bodies, and crinoids didn’t crawl. It would have been awfully hard to convince me, standing in front of that rock wall, but the slender stacks of ossicles I kept seeing were the calcified rungs of the arms of ancient sea lilies, the strange and beautiful cousins of starfish.
Most things disappear, I remember my father explaining. Hard, solid things, he said—those are what remain. Everything else breaks down and washes away.
* * *
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BEFORE MCKAY HAD departed for the ancient seabed of the Texas Hill Country, he’d tucked a SkyPager into his bag, just in case anything came up. After a couple of days of tubing, he realized the pager had been completely silent, and that silence was starting to make him nervous. On August 6, he decided to call the office on a pay phone outside the camp store, just to check in. To McKay’s dismay, the story of his rock was everywhere. The pager, it turned out, didn’t work beyond Houston’s city limits, and NASA was in a complete frenzy. Panicking, McKay’s wife and three daughters rushed him to San Antonio Airport so he could fly to Washington. The very next day, he found himself under the bright lights of an auditorium at NASA headquarters, in front of hundreds of reporters.
Just as the two-and-a-half-hour NASA press conference began, President Clinton stepped to a podium on the South Lawn of the White House to proclaim Dave McKay’s findings to the world: “Today, rock 84001 speaks to us across all those billions of years and millions of miles. It speaks of the possibility of life. If this discovery is confirmed, it will surely be one of the most stunning insights into our universe that science has ever uncovered. Its implications are as far-reaching and awe-inspiring as can be imagined…”
As McKay was introduced at NASA Headquarters, he looked befuddled in his striped shirt and space-themed tie, overmatched by the attention he was receiving. A portion of ALH84001 rested on the swath of black velvet in front of the dais. It was only 1.3 ounces, a small fraction of the four-pound rock that was collected twelve years earlier in the Allan Hills of Antarctica. When prompted, he nudged the case forward, nervously tucking his chin, and stared as the glass reflected the dazzling flashbulbs of dozens of cameras.
The directors of the National Science Foundation, the National Institutes of Health, and National Academies of Sciences, Engineering, and Medicine all sat in the front row. McKay listened as the NASA administrator boomed that it was an “unbelievable day” and as he repeated the president’s call for a sweeping White House summit on space exploration later that fall. “We’re now at the doorstep of the heavens. What a time to be alive!”
In the hours that followed, ALH84001 made headlines around the globe. Within days, almost a million people had seen the paper on Science’s fledgling website and Web alert service. Prices for meteorites soa
red at auction houses, leaping from two hundred to two thousand dollars a gram. Congress scheduled hearings. News crews swarmed like bees through the corridors of Johnson Space Center. After centuries of observation, after launching scores of probes, there was an answer to the question of life on Mars, and it had simply fallen from the sky.
* * *
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ALH84001 HAD LANDED in Antarctica thirteen thousand years ago, but it was the handful of years before its discovery that had made all the difference. Had ALH84001 been spotted and analyzed during the Viking mission, scientists would have lacked any reason to believe that a meteorite could have made the trip without being shocked and heated beyond hope for any meaningful analysis or that microbes could survive in truly punishing environments. Nor would they have had the sophisticated instrumentation available to McKay in the 1990s.
By that time, we had made giant leaps forward in understanding the limits of life. However, no researcher had ever found a microbe as small as the fossil in ALH84001. McKay had a reputation for being an extremely careful scientist. His description of the meteorite’s features was never questioned, but the implications he drew soon came under fire. Chief among the criticisms, called out prominently in a National Research Council report, was that those segmented compartments might not be big enough to encapsulate the biochemistry necessary for life.
Soon a young British researcher who’d been invited to join McKay’s team discovered some worrying signs that the organic material in ALH84001 might be of terrestrial origin, that it might have seeped in with Antarctic meltwater. Then, not long after, another research group at Johnson Space Center, led by McKay’s own brother Gordon, demonstrated that nearly identical-looking strings of magnetite crystals could form spontaneously in the laboratory. McKay quickly rebuked Gordon, arguing that artificially pure starting materials were used in those experiments and that such purity would never be found in nature. He maintained that a biogenic interpretation made the most sense and that the case for life was “further strengthened by the presence of abundant [fossil-like structures] in other Martian meteorites.” His critics countered that he had been seduced by morphology. Shapes can play tricks on the eye.
As the months went on, it was hard for McKay not to take the attacks personally. They poured in from all directions, with Gordon even jesting to reporters that his brother was getting “a little testy.” McKay would work all day and then return home late at night in his old Chevy van, retreating to the house he’d built on the floodplain, its walls covered with kimonos from the time he had spent with the Geological Survey of Japan. As the stress built, McKay stuck to his guns, unaware that a year after the announcement he would find himself in a hospital undergoing quadruple bypass heart surgery.
A remark that Carl Sagan made early in his career, that “extraordinary claims require extraordinary evidence,” was often repeated in the wake of the controversy. By the time Clinton’s White House summit on space exploration took place, Sagan was unable to stand, much less attend. He had always been the apologist for dispiriting results on Mars, the unwavering optimist, the soothsayer—but from a treatment center in Seattle, shortly before his death, he conceded that “the evidence for life on Mars is not yet extraordinary enough.” Others agreed, and the idea that ALH84001 contained fossil remains of Martian life was largely abandoned.
* * *
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HOW MAGICAL IT had been for those few weeks, how completely riveting. It seemed so unlikely and at the same time perfectly in line with the breathtaking revolution taking place in the world of biology, where the pace of discovery was accelerating. The human genome was nearly mapped, as were the genomes of many simpler organisms. Strands of DNA were being sequenced all over the world. Every type of living organism was being tacked onto a phylogenic tree, with extremophiles leading the way back to the very root of life on Earth. Within a few weeks of the ALH84001 announcement, genomic data unveiled an entirely new domain of life, the archaea: primitive microbes capable of surviving in extreme conditions that were previously unknown to science. With the discovery, biology’s five kingdoms (animals, plants, protists, fungi, and bacteria) dissolved, replaced by a system that recognized how prevalent and diverse simple, single-celled organisms were on Earth. At the same time, Dolly the sheep was cloned. Widespread harvests of genetically engineered corn and soybeans were arriving in supermarkets. Pharmaceutical companies were fanning out across the globe in search of rare, potentially lifesaving organisms, and with samples in hand, they were discovering, patenting, and commercializing bizarre new compounds. It was a heady time. And somehow fitting that a rock capable of unlocking the mysteries of life would just show up out of nowhere.
ALH84001 was a glimpse into a future brimming with possibility. What if life on Mars was completely different from life on Earth? Every organism we knew, down at the molecular level, was just the same: DNA-based, with DNA coding for RNA, RNA coding for amino acids, amino acids coming together in proteins, and proteins building cells. What if those tiny Martian cells were built on an entirely different biochemistry? Perhaps the answers were inside a meteorite. Perhaps the rock would reveal the underlying constitutional nature of life—perhaps even evidence of a separate genesis. Or, if those cells bore fundamental similarities to life on Earth, it might suggest universal laws of biology, just as there were universal laws of physics and chemistry. In these ways, when ALH84001 fell to Earth, it had landed us on the brink of discoveries so profound that they promised to transform the very nature of science.
The possibilities didn’t end there. Even if life on Mars was exactly like life on Earth—ancestrally related, caught like a cold from the next planet over—that too would be revelatory. A microbe that had hitched a ride in a meteorite could speak volumes about the nature of evolution, allowing the tape to be replayed, the adaptive and random splitting of lineages to be re-charted. It could open a window into how differently things might have turned out for us here on Earth. Maybe Martian phylogenetics would also indicate that life started in some warm little pond? Or maybe we would discover that we didn’t need to find Martians, that we were Martians? After all, countless tons of rocks, rocks like ALH84001, were exchanged between the planets early in their histories, and more meteorites were lobbed from Mars to Earth than Earth to Mars, as debris sailing about our solar system was tugged toward the sun.
In the end, ALH84001 was not what David McKay hoped it would be. But for a moment, we held in our hands what we had been after for so long: a Rosetta stone for biology.
THE FIRST INTERPLANETARY rover, the size of a suitcase, came blazing through Mars’s thin atmosphere in the summer of 1997. It had been two decades since we’d been to Mars, and we had entered a new age of robots. The Pathfinder mission was designed to test how a rover might roam across the Martian surface, remotely piloted from mission control two hundred million kilometers away. The rover was a solution to a problem as old as exploration itself: How do you study something that is very far away? Logistics become exponentially more complicated the farther you go, introducing new constraints on what can be carried, assembled, and accomplished. Lunch in a kitchen is easier, and can be more elaborate, than lunch on a mountaintop. Never was this more of a problem for science than with Viking. So much energy and effort had gone into simply getting to the surface of Mars, and yet after all those years of planning, the lander’s instrument payload could only be deployed to investigate what happened to be right in front of it. As a result, the subject of Viking’s study was a matter of chance, and there was no way to know if better scientific targets were just out of reach.
Pathfinder was meant to change that. The rover would usher in a new age of agile, real-time planetary exploration, one where each of the ongoing observations would enable adjustments to the traverse, allowing scientists to capitalize immediately on the data returned.
The spacecraft was the first in a series of low-cost missions developed unde
r NASA’s late-1990s mantra of “faster, better, cheaper.” It was designed under the leadership of an irascible NASA administrator from the South Bronx, a former aerospace-industry executive. He was determined to show that we could not only return to Mars but we could do so for a fifteenth the cost of one of the Viking missions, in half the time, using a team a third the size. In service of that goal, NASA had jettisoned the idea of slowing down in orbit for a soft landing and instead decided, for the first time, to barrel straight into a planet.
As Pathfinder approached Mars, it was the dead of night on the planet’s surface. Because the landing site was rotated away from the sun and away from Earth, the Mars scientists who had waited twenty years since Viking to get back to the Red Planet would have to wait until sunrise on Mars to know if the little rover was safe. They gathered in mission control, holding their breath as the landing sequence commenced: the spacecraft lurching toward the surface, a parachute deploying at supersonic speed. If all was well, a flotilla of protective airbags would inflate as the probe slid down a twenty-meter Kevlar tether. The spacecraft would then thud onto the ground at highway speed, glancing off the surface like a giant beach ball.
Hours later, when at last the data began to trickle in, the team realized that Pathfinder had bounced over fifteen meters into the air, bounced several more times, then settled itself on the surface of a new world. The crash landing had worked—the airbags had miraculously cocooned the rover.
The Sirens of Mars Page 10
