Researchers have long considered the ancient oceans, gently sloshing and full of nutrients, to be a likely birthplace of the first cells. Now it seems that life could have emerged in a harsher cradle: the scalding, dark world of deep-sea volcanoes. Scientists have created a molecule that may have been an important biological ingredient for life from the metal-rich black "smoke" spewed from undersea vents. The finding, reported in tomorrow's issue of Science,* raises the odds that life could have arisen deep in oceans--perhaps even in extraterrestrial underwater volcanoes, such as those speculated to exist on Jupiter's moon Europa (see yesterday's story ).
Many scientists suspect that a "primordial soup" of amino and nucleic acids spawned the first one-celled organisms, which preyed on each other. Dramatic evidence for this came in 1953, when Stanley Miller jolted a chamber of gases with electricity, creating amino acids and other basic constituents of life. But a problem emerged: Geochemists began to suspect that the early Earth's atmosphere differed from the one Miller zapped. In 1988, Günter Wächtershäuser, a patent attorney in Munich, Germany, and a chemist by training, proposed instead that the first cells were not predators, but lived on chemical energy.
Now he and Claudia Huber, a chemist at the Technical University in Munich, say they have created what might have been a key ancient metabolic molecule without having to use a rich broth of amino acids. The pair combined gases and metals known to spew from volcanoes: carbon monoxide and methyl thiol with nickel and iron sulfides. The resulting molecule, called thioacetic acid, closely resembles a metabolic chemical called acetyl coenzyme A that "is one of the most central compounds in every cell, from mammals to the lowliest bacteria," says Wächtershäuser. Like coenzyme A, thioacetic acid is "activated," or ready to react with other molecules, so the team plans to investigate whether it can build more complicated biological molecules, like lipids. Wächtershäuser speculates that cell membranes and genetic material arose later, after complex metabolic pathways developed.
The volcanic concoction has other scientists intrigued. "Nobody has done anything like this before," says Robert Crabtree, a chemist at Yale University who specializes in reactions with nickel. If the thioacetic acid represents a way to produce life without a primordial soup, he wonders if life could be present in deep water on other planets. Everett Shock, a planetary scientist at Washington University in St. Louis, says the finding is "promising" and that Wächtershäuser has "one of the more plausible theories of the origin of life."