A hilly green campus in Washington, D.C. houses two departments of the Carnegie Institution for Science: the Geophysical Laboratory and the quaintly named Department of Terrestrial Magnetism. When the institution was founded, in 1902, measuring the earth’s magnetic field was a pressing scientific need for makers of nautical maps. Now, the people who work here—people like Bob Hazen—have more fundamental concerns. Hazen and his colleagues are using the institution’s “pressure bombs”—breadbox-size metal cylinders that squeeze and heat minerals to the insanely high temperatures and pressures found inside the earth—to decipher nothing less than the origins of life.
From This Story
Hazen, a mineralogist, is investigating how the first organic chemicals—the kind found in living things—formed and then found each other nearly four billion years ago. He began this research in 1996, about two decades after scientists discovered hydrothermal vents—cracks in the deep ocean floor where water is heated to hundreds of degrees Fahrenheit by molten rock. The vents fuel strange underwater ecosystems inhabited by giant worms, blind shrimp and sulfur-eating bacteria. Hazen and his colleagues believed the complex, high-pressure vent environment—with rich mineral deposits and fissures spewing hot water into cold—might be where life began.
Hazen realized he could use the pressure bomb to test this theory. The device (technically known as an “internally heated, gas media pressure vessel”) is like a super-high-powered kitchen pressure cooker, producing temperatures exceeding 1,800 degrees and pressures up to 10,000 times that of the atmosphere at sea level. (If something were to go wrong, the ensuing explosion could take out a good part of the lab building; the operator runs the pressure bomb from behind an armored barrier.)
In his first experiment with the device, Hazen encased a few milligrams of water, an organic chemical called pyruvate and a powder that produces carbon dioxide all in a tiny capsule made of gold (which does not react with the chemicals inside) that he had welded himself. He put three capsules into the pressure bomb at 480 degrees and 2,000 atmospheres. And then he went to lunch. When he took the capsules out two hours later, the contents had turned into tens of thousands of different compounds. In later experiments, he combined nitrogen, ammonia and other molecules plausibly present on the early earth. In these experiments, Hazen and his colleagues created all sorts of organic molecules, including amino acids and sugars—the stuff of life.
Hazen’s experiments marked a turning point. Before them, origins-of-life research had been guided by a scenario scripted in 1871 by Charles Darwin himself: “But if (and oh! what a big if!) we could conceive in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc., present, that a proteine compound was chemically formed ready to undergo still more complex changes....”
In 1952, Stanley Miller, a graduate student in chemistry at the University of Chicago, attempted to create Darwin’s dream. Miller set up a container holding water (representing the early ocean) connected by glass tubes to one containing ammonia, methane and hydrogen—a mixture scientists of the day thought approximated the early atmosphere. A flame heated the water, sending vapor upward. In the atmosphere flask, electric sparks simulated lightning. The experiment was such a long shot that Miller’s adviser, Harold Urey, thought it a waste of time. But over the next few days, the water turned deep red. Miller had created a broth of amino acids.
Forty-four years later, Bob Hazen’s pressure bomb experiments would show that not just lightning storms but also hydrothermal vents potentially could have sparked life. His work soon led him to a more surprising conclusion: the basic molecules of life, it turns out, are able to form in all sorts of places: near hydrothermal vents, volcanoes, even on meteorites. Cracking open space rocks, astrobiologists have discovered amino acids, compounds similar to sugars and fatty acids, and nucleobases found in RNA and DNA. So it’s even possible that some of the first building blocks of life on earth came from outer space.
Hazen’s findings came at an auspicious time. “A few years before, we would have been laughed out of the origins-of-life community,” he says. But NASA, then starting up its astrobiology program, was looking for evidence that life could have evolved in odd environments—such as on other planets or their moons. “NASA [wanted] justification for going to Europa, to Titan, to Ganymede, to Callisto, to Mars,” says Hazen. If life does exist there, it’s likely to be under the surface, in warm, high-pressure environments.
Back on earth, Hazen says that by 2000 he had concluded that “making the basic building blocks of life is easy.” A harder question: How did the right building blocks get incorporated? Amino acids come in multiple forms, but only some are used by living things to form proteins. How did they find each other?
In a windowed corner of a lab building at the Carnegie Institution, Hazen is drawing molecules on a notepad and sketching the earliest steps on the road to life. “We’ve got a prebiotic ocean and down in the ocean floor, you’ve got rocks,” he says. “And basically there’s molecules here that are floating around in solution, but it’s a very dilute soup.” For a newly formed amino acid in the early ocean, it must have been a lonely life indeed. The familiar phrase “primordial soup” sounds rich and thick, but it was no beef stew. It was probably just a few molecules here and there in a vast ocean. “So the chances of a molecule over here bumping into this one, and then actually a chemical reaction going on to form some kind of larger structure, is just infinitesimally small,” Hazen continues. He thinks that rocks—whether the ore deposits that pile up around hydrothermal vents or those that line a tide pool on the surface—may have been the matchmakers that helped lonely amino acids find each other.