Cooking up a key chemical of life

Some scientists believe that hydrothermal vents on the ocean floor could have provided the ingredients and energy needed to create the planet’s first life. Experiments reproducing the pressure cooker conditions at these seafloor geysers have bolstered this idea by generating several of the organic compounds that cells need to grow and reproduce (SN: 1/9/99, p. 24:

Now, a team from the Carnegie Institution in Washington, D.C., reports in the Aug. 25 Science that such conditions create pyruvic acid, an organic chemical vital to cellular metabolism.

The scientists placed small quantities of formic acid, iron sulfide, and nonyl thiol—a long hydrocarbon chain that ends with a hydrogen-sulfur group—in a welded gold tube and heated the mixture to 250ºC at elevated pressures for 6 hours.

Thiol molecules, formic acid, and iron sulfide are typically found in the superheated water spewing from hydrothermal vents, says Robert M. Hazen, one of the authors of the report. For this experiment, the researchers used nonyl thiol because it’s a liquid at room temperature and pressure and therefore easier to handle in the lab than the shorter thiols present at hydrothermal vents.

Some of the experiments simulated conditions found at vents about 3 to 4 miles down in the ocean. Others reproduced pressures likely among fractured rocks a couple of miles deep within Earth’s crust, says Hazen.

All of the tests generated some pyruvic acid, but this key chemical was more abundant in experiments run at the higher pressures. Hazen says the lab-made brews also contained simple organometallic compounds, which methane-producing bacteria use like enzymes to catalyze their own vital chemical reactions. Such bacteria have been found near hydrothermal vents.

“This is the first time anyone’s been able to synthesize organometallic sulfur compounds from basic ingredients in any environment,” says Hiroshi Ohmoto, a geochemist at Pennsylvania State University in University Park. “It’s a big deal.”

Says Hazen: “We’re not saying life evolved in these conditions, but these experiments show that hydrothermal vents could be an engine of synthesis for the complex organic chemicals needed for life to evolve.”

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