World’s deepest zoo harbors clues to extraterrestrial life

Maggie Lau works in a gold mine. But what she seeks here, more than a kilometer and a half (a mile) below the South African surface, may be more precious than gold. She’s looking for life.

It’s not easy work, lit only by headlamps. At times, it can feel as hot and humid as a sauna. Some spots smell like rotten eggs, due to sulfide gas emanating from holes dug in the rock.

Until about 20 years ago, scientists weren’t even sure if life existed deep below Earth’s surface. Then in 1992, Tullis Onstott and his colleagues discovered bacteria growing on the rocks retrieved from some 3 kilometers underground. Those rocks were more than 200 million years old, at least as old as the earliest dinosaurs. And the bacteria they analyzed may have survived from that time, Onstott now says.

He’s a geomicrobiologist — a scientist who studies how microbes interact with rocks and minerals. He heads the lab at Princeton University, in New Jersey, where Lau is now a graduate student.

Scientists like Lau and Onstott now travel the world over in search of deep life. They go deep underground in mines or caverns. They drill beneath the ocean floor and in oil fields. Some of these places are near-freezing; others are hotter than Death Valley.

“The challenge is in the hunt,” says Onstott. “It’s a fantastic journey.”

And these hunts are turning up a whole zoo of microscopic creatures. Some of the deeply buried critters feed on toxic chemicals such as arsenic and uranium. One day, other scientists might tap them to clean up toxic waste. Other microbes might produce useful substances, such as new types of germ-killing medicines known as antibiotics. And perhaps most intriguing, these organisms could also help biologists learn about life beyond Earth — true extraterrestrials.

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