Further inspection of her office would shake this initial small comfort. On her desk, under a traditional ball-and-stick model of a molecule common to chemistry classes worldwide, is a copy of a test from Ziurys's course, Astronomy 522. The test's first question asks students to draw the electron configurations for a number of molecules. Our visitor, probably wearing tweed, would wonder what an astronomer was doing teaching chemistry. This thought would only be confounded by a look at Ziurys's bookshelf, filled with dozens of multicolored binders, each binder labeled with molecular nomenclature that an astronomer with even an inkling of chemistry could see were alien combinations, and one simply titled “Extragalactic Molecules.”
“Incredible!” our visitor would assert as he put the pieces together. Ziurys is both a chemist and an astronomer. She's an astrochemist, an astronomer who studies the previously unimaginable—not galaxies, stars, or planets but the molecules around and between stars light-years beyond our Solar System. Our visitor wouldn't be glimpsing just the future but also a new universe. Until the late 1960s, it was generally considered that space was simply too harsh a place for any but the simplest two-atom molecules to survive. Ziurys's bookshelves, however, hold the story of an utterly different cosmos.
When our visitor would finally ask Ziurys how she can possibly study cosmic chemistry—observing molecules so small they are too tiny to view with microscopes on Earth—the full impact of this bizarre future would hit home. Ziurys doesn't peer through a telescope to look for molecules in space; she listens for them. She's a radio astronomer. Hers is a perspective of the universe wholly unknown to astronomers before the advent of the first dedicated radio telescopes in the 1950s. Yet when she turns the Steward Observatory's Kitt Peak radio telescope toward any point in the sky, the signal-display monitor sings with the molecular signatures of vast seas of molecules stretching across the Milky Way.
By now our visitor, quite perplexed, might turn away and toward the windows for some intellectual relief—at least daylight would be the same. However, there on the ribbon of wall beneath a rectangular slit of window, he would perhaps see the strangest item of all: a framed certificate of appreciation from the US Space Studies Board. This would be fitting for an astronomer. But he would be perplexed by the committee of which Ziurys was a member: the Committee on the Origins and Evolution of Life. This astronomer isn't just a chemist; she has something to say about biology.
In 2004, when Ziurys was on the committee and the US space program was sagging from two space-shuttle disasters, President George W. Bush announced a “reinvigorating” national program of possible American missions to the Moon and eventually Mars. What the president didn't mention, or perhaps even know about, was a far grander space race already under way: an epic quest to see our cosmic selves anew. Eight years before, in a brief address to the US Congress, NASA's top administrator, Daniel Goldin, tried to galvanize lawmakers with a new vision of the American space program, a vision that didn't involve astronauts or manned spaceflight—at least not for the foreseeable future. It wasn't even ultimately about out there. It was about us. The program was Origins. “Origins is one of the boldest challenges NASA has taken on,” Goldin told Congress, “and the results could literally change the way humans think about the universe and their place in it…. It will rewrite textbooks in physics, chemistry, biology, and quite possibly, history.” Though he was the head of the US space agency, Goldin believed that the opening century of the coming millennium belonged to biology—that “the right stuff” in space research was about life. Goldin, and others in NASA's Office of Space Science, was inspired by the previous year's discovery of the first planet around a distant Sun-like star, an exoplanet. For millennia, such planets had been the stuff of myth, speculation, and, most recently, science-fiction movies such as Star Wars. Now the space science and astronomy community reacted like Alice having fallen through the rabbit hole—it had discovered a whole new cosmos, in which the notion of planets didn't end at Pluto. Goldin championed the Origins program as an interconnected weave that would extend from exploring the origins of galaxies to the origins of solar systems and finally to the origins of life itself. Tying the program together was a single guiding question: “Where did we come from?” Origins, it turned out, was too bold a program. The United States was still deeply mired in the debate over terrestrial evolution, one in which Congress had banned NASA support for the search for extraterrestrial intelligence (SETI) program it had pioneered, and one congressman had derided the program as “the search for little green men.” Without the iconic appeal of manned exploration, Origins has yet to fully take off.
However, the new astrophysical discoveries that were driving Goldin's vision kept coming, fueling science at the intersection of astronomy and biology. At the same time that President Bush was announcing the Moon and Mars missions, the seventeen members of the Committee on the Origins and Evolution of Life were writing a landmark report joining astronomy and biology. Their report, The Astrophysical Context of Life, released in 2005, was routine in format and pedigree. But the question it asked and the conclusions it drew were historic. The authors reflected on one key question: What can astronomy tell us about biology and life? While the Bush administration was fighting the Culture Wars—tacitly, when not actively, opposing the teaching of terrestrial evolution in US schools—only several blocks away from the White House, at the offices of the National Academies, the members of the Committee on the Origins and Evolution of Life had come to the conclusion that the question of evolution on Earth was a twentieth-century issue. The twenty-first-century question was a cosmic one. Their report opened with the view that “there are compelling reasons to argue that a full and complete picture of the origin and evolution of life must take into account its astrophysical context.”
The mix of biologists and astronomers who made up the committee were far from unanimous in their view of the scope or depth of this astrophysical impact. “I think everyone on that committee felt there was life elsewhere,” says Ziurys the astrochemist in her basement office at the University of Arizona. “But there are people who felt that all life on Earth…evolved here in a soup on the Earth, with no connection out to space. And there are those of us that [ran] that committee who felt that there was a connection between what is occurring out in interstellar space and…how life evolved on Earth—or any planet.” The sticking point for the committee wasn't evolution; it was the broader notion of origins. “You would be surprised how people think in silos, even in the scientific world,” says Ziurys. “If they are biologists, working with Petri dishes in a laboratory, [they think the early] Earth was one big Petri dish.”
For Ziurys, however, the ultimate key to understanding the origins and evolution of life on Earth isn't on Earth. To understand why all terrestrial life is carbon-based, why life uses only twenty of the possible dozens of potential amino acids, why iron is the metal atom around which the hemoglobin in our blood binds—to understand any of these life mysteries—we must look to the stars. For Ziurys, and a new era of scientists, our story doesn't begin on Earth; it begins with stardust.
THE THIRD GREAT REVOLUTION
Pick up a dictionary and look up stardust, or Google the word, and you'll see that it is culturally defined primarily as fantasy rather than as fact. Stardust is the title of novels, science-fiction movies, and Hoagy Carmichael's 1927 hit song—one of the most popular American tunes of all time. Most dictionaries’ definitions of stardust are similar to this one from Merriam-Webster: “a feeling or impression of romance, magic, or ethereality.” Stardust is the equivalent of fairy dust—the stuff of fantasy, intangible and elusive.
But we're in the midst of a cultural and scientific shift, and at its heart is the new science of stardust. It's captured evocatively in NASA's Stardust mission, which in 2006 became the first mission to bring back samples from a comet: 242 million miles from Earth, the Stardust robotic probe intercepted comet 81P/Wild 2, swept through the plume of dust and water that make up the
comet's translucent tail, and made it back to Earth with an invaluable cache of microscopic grains. Some of these tiny grains are literally stardust. Wild 2 was formed from a birth cloud of dust and gas that gravitationally collapsed to form the Sun, the Earth, and other planets, as well as the countless asteroids and comets that compose our Solar System—and, ultimately, you and me. The tiny grains of sand collected from comet Wild 2 have been largely unchanged for 4.5 billion years, from the time when the Earth was forming. Stardust is now the stuff not only of fantasy but of fact and science.
Stardust science isn't a term you'll find in scientific journals. I’ve coined it for two reasons. First, it captures a profound shift in our understanding of the world and the cosmos. Second, it envelops the scope, majesty, and essence of a diverse range of research, all linked by literal stardust. Stardust science has developed gradually and spasmodically at the peripheries of the established departmental sciences of astronomy, physics, chemistry, geology, and now biology. Many scientists engaged in this work don't attend the same scientific conferences. In the increasingly fragmented, niche-specific realms in which they work, they often can't understand the details, or the importance, of each other's scientific papers. They lack a common language. For example, when biologists talk about extinction, they mean the elimination of a species. When astronomers use the term extinction, they're referring to the degree to which matter between the stars blocks their view of light from a distant star or galaxy. But indicative of the emergence of a new science, other scientists are bridging these linguistic gaps and creating interdisciplinary understanding. In the process, they're reversing a two-hundred-year trend toward increasing scientific fragmentation.
At its core, stardust science is perhaps science's greatest exercise ever in integration, extending the notion of ecology into the cosmos. German zoologist Ernst Haeckel coined the term ecology in 1873 to refer to the new science dealing with the relationship of living things to their environments. He developed the word from the Greek oikos, for “house,” and logia, “study of.” Thus, stardust science seeks to find our home in the greatest environment of all, the universe. As the Astrophysical Context of Life report contends, for example, the study of the molecules of life on Earth “should be connected to topics of star formation and cosmochemistry and the origin of life.” At the heart of this integration is the new field of astrobiology, the great unifying science. It draws not just on astronomy and physics but also on chemistry, biology, and planetary geology, extending all these disciplines to the stars in the search for life's cosmic origins and connections. Astrobiologists aren't probing the universe's physical structure but rather its biological nature.
Historically, astronomy and biology are the strangest bedfellows. Those who studied cells didn't study stars, and vice versa. One group looked down through microscopes into the essence of our beings; the other looked up and away through telescopes into the depths of the cosmos. But through this searching of inner and outer worlds, some biologists and astronomers have sensed a common goal and a single connected story. The old, seemingly impenetrable wall between our evolutionary nature on Earth and the cosmic story we see around us is crumbling. Evolutionary theory is entering the space age. For stardust scientists, the focus isn't on elucidating an expanding universe but rather on an evolving one. This is not the view of a scientific fringe. It is captured in the words of another landmark document, the 2008 NASA Astrobiology Roadmap: “We must move beyond the circumstances of our own particular origins in order to develop a broader discipline, ‘Universal Biology.’…We need to exploit universal laws of physics and chemistry to understand polymer formation, self-organization processes, energy utilization, information transfer, and Darwinian evolution that might lead to the emergence of life in planetary environments other than Earth.”
Through the research of scientists like Lucy Ziurys, we are in the midst of the third in a series of scientific revolutions that have shaped our understanding of our origins and place in the cosmos. The first revolution was the Copernican Revolution, which in the sixteenth and seventeenth centuries removed the Earth from its divine locus as the center of creation and joined our planet with the other planets orbiting the Sun. Three centuries later, the Darwinian Revolution removed humanity's distinct, divine biological status to place this species in the ebb and flow of all life on Earth. We are now in the midst of a third seismic shift in our understanding of our place in the living cosmos—the Stardust Revolution. It is merging the Copernican and Darwinian Revolutions, placing life on Earth in a cosmic context.
THE ORIGINS OF THE STARDUST REVOLUTION
Stardust science emerged as the unsuspected offspring of twentieth-century astrophysics, the marriage of astronomy and physics. Astronomy in the twentieth century was dominated by the question of the physical origins of the universe. Nineteenth-century astronomers had looked up at a heavens that had no known age, size, shape, or origin. The night sky was a dark well of the unknown. Twentieth-century astrophysicists, with new telescopes and the tools of physics, have performed the greatest pull-away dolly shot in history. They've moved the camera back to reveal Earth not just as the third planet from our Sun but also as a planet nestled among billions of stars in the spiral arm of a galaxy, the Milky Way. Then, in epic fashion, the astrophysics camera pulled back even farther to give us a divine perspective of a cosmos that evokes gasps as we see billions of galaxies in an infinite universe. Today you can download to your computer monitor the latest deep-space image from the Hubble camera, confident that the universe is 13.7 billion years old (give or take 0.13 billion years) and that it will continue to expand forever.
This comprehension required great intersections of scientific theory, observation, and experimentation. These included Einstein's general theory of relativity, laying out a basis for the nature of space-time and cosmic-scale gravity; Edwin Hubble's meticulous measurements of the speed and direction of distant galaxies, revealing their increasing separation and an expanding universe; and Arno Penzias and Robert Wilson's serendipitous discovery of the cosmic microwave background radiation—a universe's birthing sounds, evidence of the big bang. The universe revealed by astrophysics is full of exotic objects: exploding stars that for months are brighter than an entire galaxy; neutron stars, stellar remnants so dense that a teaspoonful of this über-compact matter weighs more than all the buildings in Manhattan; and, at the hearts of galaxies, massive black holes—objects whose powerful gravity traps even light.
Taken together, it's an astrophysics story that culminates in the present-day Standard Model of Cosmology, the scientific theory that explains the origins and structure of the universe. This theory ties together particle physics and cosmology, and predicts the existence of, as yet invisible, dark matter and energy, thought to account for about 95 percent of cosmic mass. It provides the scientific shoulders from which physicists such as Stephen Hawking reach for a unified theory of physics, one that joins the theory of the biggest objects, general relativity, with those of the smallest, quantum mechanics. Yet, as Hawking concludes in A Brief History of Time, even this achievement wouldn't close the circle. “A complete, consistent, unified theory is only the first step,” he writes. “Our goal is a complete understanding of the events around us, and of our own existence.” How do we fit into this story of the universe?
The puzzle of our cosmic origins is the great untold science story of the past five centuries. It's been at the core of work by scientists whom we know for other work: Newton's monumental insights on gravity and light; Pasteur's legendary experiments on the microbial basis of disease; Bunsen's iconic chemistry burner; and Einstein's defining theories of space and time. It was there, sometimes as a secret, at other times as a surprise or beyond the realm of experimentation, at the core of most of the great scientific debates—evolution, the spontaneous generation of life, the origin of the universe, the nature of stars, the origin of atoms. Each debate provided an odd-shaped piece in a great jigsaw puzzle whose assembled pieces now rev
eal the outline of an incredible image barely hinted at by any one piece. This is a cosmic puzzle for which we haven't had a box-cover image to guide our assembling. We've had to grope, feeling the shape of each piece, finding edges that fit—or that seemed to fit—only later to be dramatically taken apart and rearranged, and then often with our forgetting that we'd ever arranged them otherwise. All along, we thought that this puzzle was about the world out there, about Nature or the cosmos, but not about us. Yet in that amazing tradition of outward journeys in which we find ourselves, we've created an image in which we are now faced with our own reflection.
NEW WAYS OF THINKING
Stardust science seeks to place the Earth and our existence in a historical, cosmic context. For stardust scientists, the question of biological evolution doesn't begin with the creation of the Earth but pushes back in time and space. In cosmic genealogy, the Earth is a recent arrival, only a third the age of the universe. How do we understand the origins of life in a cosmos brimming for billions of years before the Earth existed? When astrophysicists discovered the first molecules in outer space in the late 1960s, the scientists who studied them gave themselves the mongrel title “molecular astrophysicists.” They thought in physics terms about these molecules light-years away—in terms of their quantum energy states and the wavelengths of light they emitted when energized. But during the 1970s, a new breed of astronomers looked at the molecules between the stars not as physicists but as chemists—astrochemists. It was a profound difference of perspective. Where physicists see stars as objects that produce light and heat, astrochemists see stars as the source of elements and molecules, and, therefore, ultimately, life.
The prophet of this new way of looking at the heavens was the American astrophysicist turned astrochemist Carl Sagan. Sagan was above all a critical thinker. While he inspired millions as one of the great astronomy popularizers of the twentieth century, he also sought to marry this new view with new ways of thinking. His book The Demon-Haunted World, for example, explored the boundaries between superstition and science. His critical thinking as an astrochemist and astronomer led him to a singular conclusion: it's not just the Earth but the entire universe that's alive. The opening sequence in Sagan's PBS television series, Cosmos, evokes this verdant view. Sagan, standing atop a cliff on the wind-blown coast of a Hawaiian island, introduces viewers to a new story: rather than being a barren, inanimate desert of high-energy particles and black holes, the cosmos is a fertile sea awaiting our discovery. As Sagan wrote in the companion book to the TV series: “The surface of the Earth is the shore of the cosmic ocean…. Recently we have waded a little out to sea, enough to dampen our toes or, at most, wet our ankles. The water seems inviting. The ocean calls. Some part of our being knows this is where we came from.”
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