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'Lost city' offers clues to genesis of life

Ocean-floor discovery intrigues scientists

By Gareth Cook, Globe Staff, 7/12/2001

Oceanographers have discovered a naturally occurring complex of vaulting, cream-colored spires on the floor of the Atlantic Ocean, a formation so impressive they call it ''the lost city'' and predict it may yield new insights into the beginning of life on Earth.

For some 25 years, scientists have been fascinated by hydrothermal vents, otherworldly landscapes where plumes of scalding water, heated by molten rock, rise from the ocean floor and support colonies of tube worms, crabs, and primitive bacteria.

But the ''lost city,'' reported in today's issue of the journal Nature, is a new kind of hydrothermal vent, with its water heated by a chemical reaction between sea water and exposed rock. This reaction can happen in vast areas where scientists have never looked for vents, meaning there are likely to be many more such lost cities under the world's oceans, supporting colonies of undiscovered life forms.

''There is a lot more life on the sea floor than previously thought,'' said Debbie Kelley, an oceanographer at the University of Washington.

The conditions at the ''lost city'' vent are thought to be similar to those in the planet's oceans several billion years ago, when the Earth was taking form. Biologists hope that studies of the site will give them glimpses into life's first chapter, perhaps even clues to how biology might work in the oceans of other planets and moons.

From the summit of an underwater mountain called the Atlantis massif, the formation rises like the work of alien architects. A field of massive columns - one nearly 200 feet tall, the world's largest hydrothermal column - thrusts up into currents of warm rising water.

Along cliff faces, rounded whitish ledges angle out like a mushroom or the shell of a giant clam. Long filaments of micro-organisms flap in the moving water.

''The main word I would apply is `spooky,''' said Jeffrey Karson, a geologist at Duke University, who, with Kelley, dove to the site in a submarine called Alvin, operated by the Woods Hole Oceanographic Institution.

When life was first found at a hydrothermal vent more than two decades ago, it shattered traditional understandings of biology. Life at the Earth's surface is built on a food chain that begins with plants that rely on photosynthesis, using sunlight to make food.

Many hydrothermal vents, however, are so deep in the ocean that no light can penetrate. What scientists have found at the vents are micro-organisms that do not rely on the sun's energy and can live by consuming chemicals in the water.

These organisms, which can live in extremely hot, pressurized, acidic environments, have forced scientists to rethink life's basic requirements and encouraged speculation that life might thrive underneath the frozen oceans of one of Jupiter's moons, or in other equally forbidding places. And proteins from these organisms, called ''extremophiles,'' have already been put to use in biotechnology.

The discovery of the lost city could have wide implications, because the chemistry driving it is fundamentally different from that at any vent ever seen, the researchers said, meaning that the micro-organisms that live there - which haven't been studied in detail yet - could be completely different as well.

The lost city was discovered by accident, on the final days of a deep-sea geology mission in December. Late at night, when video cameras started to send up images of ghastly towers, researchers knew they had stumbled onto something important: vents in a place where they just didn't belong.

The find, near the Mid-Atlantic Ridge, created immediate excitement among oceanographers.

With a chemical analysis of water trapped in the lost city field, the researchers were able to prove that the system is driven by a chemical reaction that turns a dark green mineral called olivine into another mineral called serpentine when it is exposed to sea water. The olivine-rich rock can be exposed by a variety of geological processes.

Scientists think that even more olivine-rich rock may have been exposed to sea water, generating similar oases of life, early in the Earth's history, said Duke's Karson. This, he said, raises the intriguing possibility that life began on Earth at a place like the lost city, not at the much hotter hydrothermal vents that have been the focus of attention recently.

The scientists were also able to prove that the area is dense with an ancient branch of single-celled life known as ''archea,'' but the researchers were not well-equipped to perform a biological survey.

The researchers are hoping to get funding to make another trip to the site, but say it can take more than a year to get time with one of the few vessels able to do the work.

Karson said the ''lost city'' name was inspired by the Atlantis mountain where it was found. But he also said there is a deeper meaning in likening it to the legendary city that no one has ever found.

''It's a good lesson to us, about getting locked into a certain way of thinking,'' said Karson. ''We know so little about some parts of our planet.''

-- Anonymous, July 12, 2001

Answers

I like that line, "When life was first found at a hydrothermal vent more than two decades ago, it shattered traditional understandings of biology.

Seems like biology is constantly having its traditional understandings shattered, as it gropes its way along the path of knowledge. I have seen it many times. I wonder what the next "shattering" of their traditions will be? I think I know.

-- Anonymous, July 12, 2001