EARTH'S TINIEST BUILDERS

THE HIDDEN WORLD OF MICROBES IN THE EARTH'S CRUST

- Abha and Deepa Jain

A few miles under the Earth's surface lies a harsh world. Temperatures remain above 152 degrees Fahrenheit (67 degrees Celsius); little pools of water within crevices are unpleasantly hot. No light and little air penetrate such depths. Surely nothing could live here.

But look closely. Those pools and rocks teem with tiny critters. And not just any critters. Some scientists now think these itty-bitty creatures have played an outsized role in creating the Earth itself.

Champs of the Extreme

Thousands of natural features freckle our planet, from deep valleys to majestic caves. You probably think physical forces such as howling winds and roaring rivers or events such as volcanoes and earthquakes carved them out. Maybe you believe potent chemicals, like rock-dissolving acids, were responsible, too.

For centuries, most scientists shared such opinions. But now, some have a different take. They reckon that microbes are just as important as physical and chemical forces in shaping our planet.

Many of these scientists are geomicrobiologists (quite a mouthful!). In Latin, geo means "rock," micro means "small," and bio means "life." Such researchers study tiny microbes, including bacteria, fungi, and viruses, that sculpt the Earth but largely live beneath its surface.

These subsurface microbes dwell in extreme environments. In the Arctic tundra, bacteria looking like mini foam-balls flourish in pockets of super-salty water tucked within the soil. Near Japan, dark blotchy fungi swell amidst coal fragments 1.25 miles (2 kilometers) beneath the ocean floor. In South Dakota's Homestake mine, white stringy chains of bacteria float in broiling puddles 8,000 feet (2,438 meters) below the ground.