Oct. 8, 2004 — Mount St. Helens' recent eruption may be replaying a scene straight from the geochemical drama that led to life on Earth.

Besides ash and lava, most volcanoes also release a toxic gas called carbonyl sulfide (COS) that has now been shown to cause amino acids in Earth's primordial soup to form chains — a very big step in the walk toward the first life.

"It's plausibly the missing link, in our thinking," said Reza Ghadiri of the Scripps Research Institute.

Ghadiri and his colleagues Luke Leman and Leslie Orgel presented their COS discovery in this week's issue of the journal Science.

For years, scientists have been trying to figure out how amino acids started getting together in strings of twos and threes, called peptides, on early Earth. The step is important because you need peptides to build the huge RNA and DNA molecules that are essential to life as we know it.

"There are multiple ways you can make peptides," said Ghadiri.

Not many of those ways, however, would be very efficient or likely under the conditions of early Earth.

Suspecting that COS might be an unsung hero, Ghadiri and his colleagues exposed a watery solution containing amino acids to COS at room temperature. It worked. The COS produced ample peptides. The researchers got even more peptides if they added dissolved metals like lead or iron to the mix.

"We tried it even in ocean water and it works," said Ghadiri. "It's quite efficient."

Not only does COS do the trick, but there is every reason to believe it was common on Earth near volcanic craters on land, as well as at undersea hydrothermal vents, billions of years ago, said early life researcher George Cody of the Carnegie Institution.

Although no one knows exactly what Earth was like when this happened, it's likely that the first peptides were made when amino acids on rocks near volcanic eruptions were exposed to COS and grew into peptides, said the researchers, a process called polymerization.

The rocks could have even provided some of the metals that make even more peptides possible. This scenario is what they are calling "polymerization on the rocks."

"I think it's beautiful," said Cody about the COS discovery and its place in filling in at least one blank in the geochemical sequence that led to life.

Of course, it's still a long way from peptides to DNA, he said, but this is an essential step in the right direction and a landmark piece of research.