Miller's results landed in an already bubbling biological pot of change. They were published in May 1953, less than a month after the momentous publication by James Watson and Francis Crick revealing the structure of DNA, the long-sought-after genetic molecule. Suddenly the question of the molecular origin of life was so much more than conjecture. Here now were the molecules of inheritance, DNA, and its handmaiden, amino acids, the molecules that join to form the proteins that are the core structural molecules of life. It was the dawn of a new kind of biology, molecular biology, in which the nature of life wasn't focused on species of animals but on the interplay of molecules—molecules that biologists now knew could form, in many cases, from the cosmos’ basic building blocks.
This didn't mean that Miller had shown how life had actually started, though certainly some were drawn to this Promethean promise; that in the hyperbole of the Cold War, somehow they'd nailed the greatest scientific problem on their first try. After a presentation by Miller of his results to University of Chicago colleagues, Harold Urey famously quipped to Enrico Fermi that “if God didn't do it this way, he overlooked a good bet!”
Today, the exact nature of the Earth's first atmosphere—and the rate at which it changed as a result of volcanic discharges, atmospheric chemistry, the impact of meteorites and comets, and the eventual rise of life—is a hotly debated topic. Most geoscientists don't think the primitive atmosphere was as reducing, or as hydrogen rich, as the mix of chemicals in Miller's glassware. Instead, views range widely from a mildly reducing atmosphere—with greater amounts of nitrogen, water, and carbon monoxide—to one that was relatively oxidative—with yet greater amounts of water, carbon dioxide, and sulfur dioxide. Similarly, the locale of interest for protean chemistry had moved from the atmosphere to volcanic plumes and the ocean bottom, particularly the chemistry around “hot smokers,” the mineral-rich hot vents on the ocean floor. What Miller's experiment did clearly show was the ability to gather the knowledge and skills to imagine the Earth as it was four and a half billion years ago and then re-create, in the most rudimentary form, the ingredients and conditions present when there was no life, only an organically rich planet, pregnant with promise.
Just months after Miller presented in Moscow, his results and Oparin's vision were about to take off into a whole new dimension: the space age.
LIFTOFF FOR EXOBIOLOGY
Like thousands of others in Calcutta, India, on the night of November 6, 1957, John Haldane and Joshua Lederberg occasionally glanced at the full Moon in anticipation of its imminent disappearance. Calcutta's stifling summer heat was subsiding, and the two men shared a rooftop dinner in the relatively cool evening air, waiting for the lunar eclipse. While others in the city talked about what the eclipse might portend for good or evil, few—if any—talked about the new scientific age that Lederberg foresaw. The thirty-one-year-old American microbial geneticist had come to visit one of his heroes, the British geneticist J. B. S. Haldane, who at the age of sixty-five had recently moved from London to Calcutta. They'd both been disappointed to miss the Moscow Origins of Life conference; Haldane, because of his move to Calcutta; Lederberg, because of work in Australia.
Lederberg, a New York rabbi's son, turned several generations of zeal for Talmud study into a precocious passion for the reproductive workings of bacteria. In 1946, at the age of twenty-one, he broke biological orthodoxy by showing that bacteria were not only far more genetically complex than previously thought, but that a type of bacterial sex—gene swapping—was going on, a discovery that won him the 1958 Nobel Prize in Physiology or Medicine. Lederberg was a rare breed of scientist with a deeply visceral sense of his field, one who integrated new events into a boiling pot of ideas and who thought deeply about their concrete consequences. For his part, Haldane was second only to Oparin as a father of twentieth-century reflection on the origin of life. In the 1920s, Haldane had been deeply involved in the development of evolutionary genetics, which, coupled with the discovery of viruses—remarkable microscopic organisms that appeared half-alive and able to survive only when infecting a host cell—set Haldane to thinking about evolution that might have occurred before the first cell, or even the first virus.
In 1929, five years after Oparin's initial pamphlet version of The Origin of Life appeared on Moscow's streets in Russian, Haldane independently, and without access to Oparin's work, published his own doppelgänger English version, also titled The Origin of Life. Both scientists were riding the same wave of insight: that the primordial conditions of the early Earth atmosphere had been vastly different from those of today and had been the site of organic synthesis that turned the Earth's early oceans into a primordial soup of life's building blocks. As a result, there wasn't an impassable abyss between the complexities of the cell and the relative simplicity of the foundational organic molecules; self-reproducing organic molecules might be an intermediate link between seemingly inanimate matter and life.
As Lederberg and Haldane talked intensely that night, the Moon became a source of great expectations and deep concern. For millennia, the Moon had been a harbinger of Earthly events, and now the question was not just what the Moon could do to the Earth but what Earthlings might do to the Moon. Just a month earlier, on October 4 (a month after Oparin's meeting), the Soviet Union had launched the world's first satellite, Sputnik 1, and with it, the space age. Lederberg and Haldane, both perennially at the forefront of their respective disciplines, were awed by this technological leap and the prospect of where it might lead. Their conversation turned to a disturbing possibility. What if, to mark the upcoming fortieth anniversary of the Bolshevik Revolution and make the ultimate display of power, the Soviets were to detonate a nuclear bomb on the Moon—to symbolically put a Red Star on the Moon? The idea would have seemed ludicrous several years earlier, but under the Calcutta Moon, it appeared completely possible. Two years earlier, the Soviets had detonated their first megaton-scale hydrogen bomb. The past summer, Soviet rocketeers had launched their first intercontinental missile, blasting it an impressive and terrifying four thousand miles. Now, humans really could reach out and touch what had hitherto always been out of reach.
To Lederberg, the once faraway and pure Moon appeared deeply vulnerable. Not just its cratered face but also potential lunar microbes that he believed could hold the key to understanding the origin of life on Earth and possibly beyond. Yet, before rockets were used to explore the Moon, the real prospect existed of contaminating it with nuclear waste. As a microbiologist, Lederberg knew how easy it was to contaminate a sample and destroy an experiment; he was also aware of the ubiquitous and exponential growth of bacterial populations. For Lederberg, this wasn't just late-night, alcohol-fueled speculation to be forgotten the next morning. More than any other biologist, he saw rockets and satellites not just as announcing the dawn of the space age but also as introducing a new age of biology. Here was an amazing and unique opportunity to explore another celestial body for life, an opportunity that could be ruined by national grandstanding or ignorance. The answer to Darwin's gap might lie within reach on the lunar surface, but humanity might spoil its once-in-a-civilization opportunity.
Returning to the United States, Lederberg began a determined one-man campaign to raise concern about lunar contamination, whether by radioactivity from a superpower nuclear stunt or by inadvertent bacterial contamination from a lunar rover. It was a campaign that would mature into NASA's planetary protection program. “Since the sending of rockets to crash on the moon's surface is within the grasp of present technique,” Lederberg wrote in a paper published by the journal Science in June 1958, “while the retrieval of samples is not, we are in the awkward situation of being able to spoil certain possibilities for scientific investigation for a considerable interval before we can constructively realize them.” Politicians, bureaucrats, and scientists listened to Lederberg, even more so after the autumn of 1958, when his Nobel Prize was announced. One of the upshots of Lederberg's campaign was the US Department of Defense P
roject A119, launched the same year, in which a young astronomer named Carl Sagan was hired to make calculations of the results of a lunar nuclear blast.
Also in that year, President Dwight D. Eisenhower officially entered the United States into the space race through the National Aeronautics and Space Act, creating NASA as the US space agency. Soon after, NASA's first deputy administrator, inspired by Lederberg, asked the National Academy of Sciences to set up a Space Sciences Board to advise NASA. The Space Sciences Board was divided into several subpanels, including one on extraterrestrial life, the forerunner of the Committee on the Origins and Evolution of Life. Its first chairman: Joshua Lederberg. But as Lederberg immersed himself in astronomy papers and talked with the committee members he recruited, including Harold Urey and Carl Sagan, he saw that what they were discussing was something much bigger than preventing lunar contamination. The space age was also liftoff for a new science. Lederberg dubbed it “exobiology”: biology beyond Earth. “Twenty-five centuries of scientific astronomy have widened the horizons of the physical world, and the casual place of the planet Earth in the expanding universe is a central theme in our modern scientific culture,” he wrote, in what appears as a precocious précis of the Stardust Revolution.
The dynamics of celestial bodies, as observed from the earth, is the richest inspiration for the generalization of our concepts of mass and energy throughout the universe. The spectra of the stars likewise testify to the universality of our concepts in chemistry. But biology has lacked tools for such extension, and “life” until now has meant only terrestrial life…. For the most part, biological science has been the rationalization of particular facts, and we have had all too limited a basis for the construction and testing of meaningful axioms to support a theory of life.
Exobiology could address Darwin's gap by providing comparisons not only by studying life on Earth but also, Lederberg envisioned, by comparing terrestrial molecules with molecules on the Moon. Four years earlier, President John F. Kennedy had stood in Houston's Rice Stadium and delivered his famous “We choose to go to the moon” speech. Now Joshua Lederberg was envisioning that day and what it would mean, not for engineering, geopolitics, and the history of human adventure, but for understanding our origins.
The seeds of something profound had been planted in his mind that Calcutta night. Lederberg, the biologist, saw the Moon not as distant and other but as sharing a common lineage, one that might be preserved on the lunar surface. He thought that the Moon's ancient cratered surface might contain prebiotic molecules untrammeled by the geological processes that have transformed the Earth. In his article “Moondust,” Lederberg sounded more like an astronomer, referring to a new upstart field that was challenging the way astronomers viewed the heavens. Lederberg argued that the keys to understanding the origins of life on Earth might be found in the microscopic pores and surfaces of moondust. The Apollo missions might be the equivalent of Darwin's journey on the HMS Beagle, providing vistas for contrast and comparison.
But it wouldn't so much be dust from the Moon that would deepen our understanding of our origins. Rather, it would be something that, after millennia of stargazing, astronomers had only just begun to glimpse: cosmic dust. With all eyes on the Cold War race to the Moon, it was technology from an earlier war that would open astronomers’ eyes to a whole new realm, a realm between the stars.
We now know that our origins lie in the dust of interstellar space, that our Earth and ourselves are condensates of the dark gaps between the stars, the same yawning expanses that are visible within the Milky Way on any clear night.
—James B. Kaler,
Cosmic Clouds: Birth, Death, and Recycling in the Galaxy,1997
THE ORIGINAL DARK MATTER
For anyone pitching possible venues for a family holiday, Canada's Grasslands National Park might not sound at first like a must-see destination. In fact, when I made the suggestion to my wife, she asked, “Why would we go to somewhere called Grasslands? What are we going to see, grass?” She's far from alone in this opinion. Located in the extreme south of the province of Saskatchewan, just north of the Montana border, near the middle of the North American continent, Grasslands is one of Canada's newest and least-used national parks. And yes, there's a lot of grass. The park protects one of the few remaining stretches of North America's bald prairie. Most of the North American prairie has been paved, plowed into wheat and canola fields, or pastured into cattle range. But Grasslands National Park is semiarid, receiving mere millimeters of rain a year more than a desert. It is land too marginal for even the most failure-hardened farmer.
I realized while camping at Grasslands that what makes it remarkable is that you go not to see things but to be seen. Not by other people but by the elements. Of course, there are lots of sights: the majestic flat-topped buttes with views across glacial-spillway-carved valleys, the spectacular flowering prickly pear cacti that appear as bursts of color amid the grasses, and the bison, their powerful humped shoulders silhouetted against endless distance. Most of all, though, in Grasslands National Park, there's the sky. Saskatchewan's vehicle license plate motto is Land of the Living Sky, a phrase that captures something as ephemeral, fleeting, and yet powerfully real as a towering thundercloud looming over the land on a scorching August afternoon. Here, on the flat, bald prairie, the sky swallows all. You watch menacing storms move in from the distant horizon; the weather forecast there for the seeing. Above all, it is the Sun, in all its blazing glory, that is omnipotent. There is nowhere to hide—no shade, no place where you can escape the Sun's gaze.
When the Sun sets, though, the sky turns from stunning to sublime. This is when Land of the Living Sky takes on new meaning. Grasslands National Park is a dark-sky preserve, part of a current global trend to protect not just threatened habitats and species of animals and plants but also the simplicity of the truly dark sky, free from human-caused illumination. In this sense, Grasslands is about as good as it gets in the easily car-accessible parts of North America—in the center of the park, you're about twenty miles from the closest porch light or streetlight.
In the early morning hours, I awake to look at the stars. I’ve seen many a deep, dark night sky, but this view engenders awe. Over the buttes and valleys, the Milky Way spills from horizon to horizon, a great slit of luminescent eye, like some celestial sea creature peering out from the darkness. I know I am looking edge-on into the heart of our galaxy, seeing the cumulative light of hundreds of millions of stars. It's so bright I could read a book by the light of these distant suns.
What's also clear in this deep dark of night is that, for all its stars, the Milky Way isn't all light. There are dark lanes. Not the gaps of darkness between the stars, but here and there great swaths of darkness, starless eddies in the galactic stream. Here, or at sea, or in those remote corners of our globe where the night sky is still wild, it's not just the stars that stand out; it's the darkness. What I peer into over Grasslands National Park is a crucial piece of the Stardust Revolution: the mystery of the original dark matter.
For astronomers, the term “dark matter” has long referred to something that appears to be out there—usually observed, by implication, but with no explanation in the existing astrophysics or cosmology. The search to explain today's dark matter, the sought-after and wonderfully named phantom weakly interacting massive particles (WIMPs), is inferred through the need for more matter to explain the gravitational behavior of galaxies. The dark voids of the Milky Way were astronomy's original dark matter. In them, we would discover an intimate link between darkness and light, the birth and death of stars, and our own dusty beginnings. The astrobiologist Joshua Lederberg had imagined moondust as holding the secrets of human origins. But we'd have to travel far beyond the Moon to find our stardust past.
These dark patches amid the stars have intrigued stargazers for millennia. The Inca of Peru, deeply reverent stargazers from mountain sites such as Machu Picchu, gave descriptive names to the dark constellations they saw in the Mi
lky Way: a writhing patch of darkness was “the serpent”; a blob, “the toad”; a large patch, “the llama”; and, best of all, a rope-shaped extension of the llama was dubbed “the umbilicus of the llama.” As European astronomers from the seventeenth century used telescopes to probe deeper into the heavens, they discovered not just stars but also a surprising menagerie of relatively dark, blurry patches of a variety of shapes and sizes—smaller versions of the Milky Way–scale dark swaths. There were also intermediate luminous objects—though not stars—that were dark, but not totally dark. Astronomers dubbed these stationary fuzzy objects nebulae, Latin for “clouds.” The term captured both the similarity of their appearance to terrestrial clouds and the nebulous nature of early astronomers' understanding of them.
The most famous of these nebulae, the Orion Nebula (also known as M42 or Messier object 42), was first reported by Nicolas-Claude Fabri de Peiresc in 1611. In the late 1700s, the great British astronomer William Herschel described small, glowing clouds that he called planetary nebulae because of their circular shape (thus sowing seeds of confusion for future generations because these nebulae aren't related to planets but to dead stars), made from “a shining fluid of a nature totally unknown to us.” By the early twentieth century, as some astronomers categorized star types, a smaller group turned to mapping the dark bits between the stars. In 1919, the American astronomer E. E. Barnard, after years of observing (while wearing his caribou-skin coat to stay warm), amassed a catalog of almost two hundred dark objects. Barnard was convinced that these dark clouds weren't just starless gaps of empty space but rather that they were some thing, some dark matter in the heavens obscuring starlight in these regions.
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