Weekly Bulletin
December 13, 1999
Vol. 89, No. 12
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Two miles underground ... studying subsurface microbes
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Nassau Notes

Grants available


Two miles underground

Gold mines present "ideal environment" for geologists studying subsurface microbes


Duane Moser (l) and South African ventilation engineer Cosolomon Kuhmalo (Photo by Brett Baker)


By Steven Schultz

Forr his first assignment as a post-doctoral scholar at Princeton, Duane Moser stepped into a steel cage and dropped two miles into the earth.

Heat, darkness and air pressure closed in as he plummeted downward at 40 miles per hour, shoulder to shoulder with about 30 miners. Their destination was the bottom of Shaft No. 5 in East Driefontein Gold Mine, 60 miles southwest of Johannesburg, South Africa.

Moser's quarry was not gold but microbes living deep in the earth, life forms so ancient and so alien from anything seen on the surface that they could lead to a new understanding of the origin of life on earth as well as life on other planets.

It was the start of what would become a routine of working in the lab of Associate Professor of Geosciences Tullis Onstott, who has been studying microorganisms from deep beneath the earth since 1994. Onstott recently received a $3 million grant from the National Science Foundation and NASA to establish a permanent research station in a South African gold mine.

"These mines present an ideal environment for getting at samples of rock and water from the deep subsurface of the earth," says Onstott. Not only are they deeper than other mining operations, the extensive tunnel systems allow scientists to move between rock formations and pick the samples they want. That mobility, says Onstott, could aid the discovery of novel organisms, as well as the creation of a map that describes how the microbes and the rock have evolved.

Already Onstott's research has shown signs of microorganisms that eke out an existence in minute cracks within the rock, sealed from oxygen and scorched by radiation and extreme heat.

Deep and dark and hot

Onstott has been researching deep subsurface microbes for the past six years as part of a Department of Energy program focusing on several US drilling operations. Looking for further research opportunities, he made his first foray into a South African gold mine in 1996, with the help of a former graduate student, David Phillips, who worked for a gold mining company at that time.

"It was one day, in and out," Onstott recalls. "I flew in and went down a hole. It was 'Don't step there, don't touch that.' All I knew was that it was deep and dark and hot."

On the plane home that night, Onstott didn't think about the discomfort or the danger. He worried about getting his sample to a lab quickly enough to find something useful. And he did: "a very interesting organism" similar to microbes found in boiling hot springs.

That discovery confirmed Onstott's hunch that gold mines contained a secret microbial life that was worth much more study. At about the same time, two other developments in science helped convince funding agencies to share his enthusiasm.

Tullis Onstott (Photo by Louise Gubb)



Researchers from Pacific Northwest National Laboratory in Washington State had published a landmark paper in Science describing how microbes can live off tiny amounts of hydrogen released by slow oxidizing reactions in rock. Such a novel metabolic system could allow life to exist in anaerobic, sunless environments previously thought to be entirely inhospitable.

Then in the summer of 1996, news broke that scientists had found signs of life in a Martian meteorite. Although that finding was later questioned, it sparked considerable interest in looking for life in the Martian subsurface.

"Talk about serendipity," says Onstott. "But all of us in the DOE program knew that if you find good evidence of environments that support life in the deep subsurface of Earth, then the chances are high that you will find these environments beneath Mars as well."

In the fall of 1997, Onstott secured a small grant from the National Science Foundation and, along with researchers from the University of Tennessee, pulled together a team of about dozen geologists, microbiologists and hydrologists to make more forays into South African mines.

One of his first tasks was to recruit a postdoc. He found Moser, who had just finished his PhD in microbiology at the University of Wisconsin, where he worked on methods that might be used to analyze rock samples from future missions to Mars. Moser also knew his way around underground as "a semi-hardcore recreational caver."

A healthy fear

Through a series of delicate negotiations, Onstott and his colleagues secured an agreement for access to a mine. Starting in the fall of 1998, Onstott made periodic trips between Princeton and South Africa, while Moser lived at the mine site, going underground almost every day with the miners.

"It was much more dramatic than any cave I'd been in," he said. "There was fear--a healthy fear--that was with me all the time."

The air pressure at Moser's work site was double what it is a sea level. The temperature of the virgin rock is 140°F. The mines must be continually flushed with fresh air from above to keep the heat below body temperature and to remove toxic gasses.

The tunnels stretch for miles from the main shaft to where the mining is done. At the workfaces miners and scientists move at a crouch because the sloping cavity that chases the pencil-thin stratum of gold is only about five feet tall maximum.

"The footing is bad; it's noisy; you can't see; there's dust all over the place; and the noise of the air hammers is incredible," says Moser. In that oppressive environment, the scientists built close ties with the miners, whom they relied on for everything from avoiding danger to hauling their chunks of rock out of the mine.

During the winter of 1998-99, Moser studied rock and water samples in a makeshift lab and was host to a dozen other researchers from around the world who came to collect samples.

Water seeping into the mine presented one of the best scientific resources. "It's a problem for the mine, but it's a great opportunity for us," says Moser. The scientists can collect a pristine sample that has not seen the earth's surface in millions of years.

It is now clear, says Onstott, that the samples from East Driefontein Mine contain a wealth of interesting data. Moser has isolated the DNA of several microorganisms from these samples.

How do the organisms survive under such adverse conditions? Onstott theorizes that microbes could live off of hydrogen that gets split from water by radioactivity in the deep rock. "Hydrogen gas is like junk food to a lot of bacteria," he says. It's not an easy life, however. The food supply is so sparse that the bugs reproduce maybe only once in a thousand, or perhaps even a million years. That means organisms the scientists are seeing today have had little opportunity to change since the earliest history of life on earth.

That possibility is intriguing not only to geoscientists and biologists, but also to those interested in exploring life on other planets.

NASA could begin using Onstott's findings about subsurface environments during missions to Mars that will take place within a decade, said Michael Meyer, a NASA staff scientist who reviewed Onstott's grant.

In the meantime, Onstott and Moser are eager to go back under ground in South Africa.

"With this first round of samples," says Moser, "we learned a lot. But the next time we can do it better. It's a great adventure."