Thermal vents spew mineral rich fluid as hot as 350 degrees INTERACTIVE     Explore life at its extremes

April 1, 1999
Web posted at: 5:11 p.m. EST (2211 GMT)

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By Richard Stenger
CNN Interactive

(CNN) -- Neil Armstrong received the glory as the first astronaut on the moon, but other earthlings actually beat him to the surface by two years. Stowaways on the Surveyor 3 spacecraft in 1967, a colony of the streptococcus mitus remained stranded on the moon until a rescue several years later by astronauts, who brought the harmless, common bacteria home where they were revived.

More than 30 years later terrestrial microbes again are pioneers in space research, but these hardy life forms are far from ordinary. They thrive in volcanic vents, bubbling cauldrons and deep sea oil deposits. They eat rocks, sulfur and silica.

In the past scientists presumed life on Earth existed within comfortable, familiar parameters. It needed water, oxygen, carbon and light, and couldn't exist in extremes of temperature, salinity or acidity.

But scientists across the world are increasingly finding life in unexpected places. And many of the forms are so different that they've require an entirely new classification, separate from plants, animals and bacteria: archaea.

Biologists, chemists and geologists with the Astrobiology Institute, a NASA-led consortium of 11 preeminent research centers established earlier this year, are taking a closer look at life at the extremes. Their research on this planet could offer clues about possible life elsewhere.

"Until we know the limits of life on Earth, then it's really hard to say what the limits in space would be," said Bruce Runnegar, Director of the Center for Astrobiology at the University of California, Los Angeles, one of the consortium members.

Europa

Those limits have expanded everywhere on Earth. Off the coast of Italy, a deep-sea diver in January collected samples of heat-loving microbes in a thermal vent near an extinct volcano.

Such hyperthermophiles, or lovers of extreme heat, could teem in hot vents and volcanic fissures that for tens of thousands of miles crisscross the ocean floors like seams on a baseball. The cracks spew molten lava, blistering water and microbial life.

Off the coast of Oregon, U.S. scientists studying volcanic activity discovered signs of life on an otherwise icy ridge 1.5 miles below the surface -- odd-looking colonies of heat- loving microbes characterized by long tendrils or whitish clouds. The natural undersea rock chimneys, called everything from snow blowers to smokestacks, issue mineral-rich fluid as hot as 350 degrees C.

Other heat lovers can thrive in deep-sea petroleum deposits with temperatures of more than 176 degrees C (350 degrees F). Renowned German scientist Karl Stetter isolated some of them deep below the bottom of North Sea. With oxygen and light scarce or non-existent, the microbes lived off the gases and organic acids caused by geochemical reactions.

Similar archaea live miles underground in aquifers heated by the Earth's core. For nutrition they rely on water and nutrients in the rock.

Some scientists estimate the total biomass of the subterranean life surpasses that on the surface by two times. Dr. John Baross at the University of Washington suggests primordial life took root deep within to avoid the barrage of meteorites and radiation on the surface.

Such organisms, theorizes Cornell scientist Thomas Gold in his 1998 book "The Deep Hot Biosphere," are the remnants of the first life forms on Earth. And some think they could resemble life forms elsewhere in the universe where similar conditions are present.

The discovery of more planets outside the solar system than in it has made scientists increasingly confident that life could exist far beyond our familiar blue sphere. Even some planetary neighbors in this solar system hold promise.

The surface of Mars as captured by Pathfinder

The moons of two gas giants further from the sun are candidate sites. Underneath its ice crust, Europa could have oceans and volcanic vents. Signs of volcanism have already been observed on Io, leading some scientists to wonder whether thermophilic life could exist deep within.

Titan, which has a thick nitrogen atmosphere, is another possibility. And further out in the far reaches of the solar system, Chiton, a large asteroid near Pluto, could hold a liquid ocean.

Searching for indications of life, NASA has missions in the works to Europa and Titan early in the next millennium.

Later this year, two probes are expected to land on Mars, looking for signs of water.

But the most promising evidence of extraterrestrials could also turn up on the red planet. Scientists theorized in 1993 that a meteorite from Mars found in Antarctica, known as the Allan Hills 84001, contained fossilized signs of bacteria-like life 3.6 billion years old.

More recently, the same NASA team announced that two other meteors thought to be from the red planet could contain similar fossilized remains.

The latest findings were from samples of a 1.3 billion-year-old meteorite that fell to Earth in 1911 near Nakhla, Egypt and a 165 million-year-old meteorite that fell near Shergotty, India in 1865.

If Martian bacteria once resided in these much younger rocks, then life may have persisted on the red planet through a drastic and still unexplained climate change.

"If this proves out, we will have shown that life spanned almost the entire history of Mars, and presumably today," said Johnson Space Center geologist David S. McKay. "Nothing has happened in the last 165 million years that would kill off life on Mars."

The Associated Press and Reuters contributed to this report.

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