St. Louis Post-Dispatch

ST. LOUIS, Mo. – There are some very old skeletons in Timothy Kusky’s rock closet.

The St. Louis University geologist takes a blistered rock from a dusty closet drawer. The rock, the size of a half-basketball, sheds some black soot, but otherwise it’s doing pretty well for 2.5 billion years old.

Fingers jut out from the rock. Inside these tubes are faint rings that enclose tiny white crystals, which under a microscope look like thin sausages. Kusky says he has the carbon signature to prove that what he sees was once alive: fossilized microbes that fed within the superheated, sulfurous tubes of a sea floor chimney.

These rocks are the oldest known sea floor rocks with life. Kusky’s find is the oldest evidence of what many scientists believe: that the sea floor, with its hot, mineral-rich water, would have been the only place nurturing enough to support life on Earth, early after its formation 4.5 billion years ago.

“The speculation is, this would be where life first evolved on the planet,” Kusky said.

Kusky made geological headlines four years ago when he found the sea floor rocks, high in a Chinese mountain range northeast of Beijing. The first rocks he found were fused, lifeless things from well below the ocean floor. He wanted to find the chimney rocks, since the sulfide-spewing vents that build the chimneys also can support life.

Kusky is 43 with a touch of gray to his sideburns. He talks like a teenager: fast, his lips barely moving. From memory, Kusky quickly sketched a map showing how he zeroed in on the rocks, known as black smoker chimneys. He hopped up onto an office chair in front of a computer. Squatting with both dress shoes pressed into the cushion, he flashed a computer slide of the intimidating Wutai Shan mountain peaks.

He trekked across the Wutai Shan mountains over a dozen trips, finally finding his quarry on a rainy summer day two years ago near a village called Stonemouth. Pressed within a rock outcrop was a recognizable chimney surrounded by chunks of sulfide deposits.

He washed the rocks in hotel bathtubs and shipped them back to the United States in book boxes, 50 bucks apiece. Recent chemical analysis on thinly sliced rock cross-sections shows that the microfossils contain carbon, a sign that they were alive. Kusky has submitted the work for academic review.

How the rocks got from an ocean floor to a Chinese mountainside is a story millions of years long. Hot magma fuels the splitting of an ocean plate at a midocean ridge. (It also provides the heat that drives sulfurous water to build black smoker chimneys.)

Eventually, the spreading, heavy ocean crust encounters a continent and dives under it. Some of the sea floor rocks can be scraped off and later lifted to the surface during a period of mountain building, said Stephen Mojzsis, a geologist at the University of Colorado at Boulder.

“This is cool because it’s far easier to drive up to these things and sample them, then to go down in bathyscaphes and look at them at the bottom of the ocean,” he said.

The deep-sea submersible Alvin first found black smoker chimneys in 1977 of the coast of the Galapagos Islands. Scientists were surprised to find clams and tube worms thriving in the 500-degree pitch dark. The animals fed on bacteria that in turn ate the sulfur percolating from sea-floor vents. It was the first ecosystem not dependent on sunlight.

These and other heat-loving “extremophiles,” like microbes found in Yellowstone Park hot springs, have DNA that has barely changed, Mojzsis said. In other words, he said, they have “ancient pedigrees” that extend further back in the tree of life than any other type of organism.

Geologists offer another reason life began on the sea floor: It might have been the only place possible. From the time the Earth formed, 4.5 billion years ago, until about 3.8 billion years ago, large meteorites slammed into the earth. Geologists have a name for it: the Heavy Bombardment Period.

“It resulted in catastrophic environmental conditions: a boiling ocean, raining molten rock, a steam and rock-vapor atmosphere. It’s a bummer. However, if you’re a microbe at the bottom of the ocean, and you’re acclimated to temperatures barely above the boiling point of water anyway, what happens at the surface means nothing to you,” Mojzsis said.

Kusky next wants to push the timeline for life-bearing sea floor rocks back by another billion years. He wants to go to the Pilbara region of western Australia, where he thinks he might find sea floor rocks 3.5 billion years old. If he’s lucky, he’ll bag some black smoker chimneys. Mojzsis said Kusky will need the luck.

“Dude – I’ve been there three times and whacked about the bush with some great field geologists. We think we see something … but not a single microfossil,” he said.

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(c) 2005, St. Louis Post-Dispatch.

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AP-NY-04-01-05 0621EST

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