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Life Thrives Deep Down Underground

Tiny worm lives more than a mile down

A subterranean worm, photo by Gaetan Borgonie

More than 9,000 feet below ground, small worms are alive and well – and raising new possibilities of how life may exist on other planets.

The discovery of halicephalobus mephisto, a roundworm, has scientists totally revising their understanding of what kind of animals can survive, indeed thrive, in places they never imagined.

Scientists have long known that bacteria can live deep underground, but when a small team went deep down into a South African goldmine, they found a worm living in the pressurized atmosphere, in total darkness, at temperatures that exceed 100 degrees, and where the only food is bacteria. Lead biologist Gaetan Borgonie of Belgium’s Ghent University reports on their findings in the journal Nature.

Halicephalobus is very small – about two hundredths of an inch – and is classified as a nematode. We know of about 28,000 kinds of nematode, and many of them can live almost without oxygen, in extremely acidic environments, and despite prolonged starvation.

Borgonie says he has developed “a healthy respect for their ability to withstand stress.” For example, when the space shuttle Columbia disintegrated upon re-entering Earth’s atmosphere in 2003, roundworms in a canister on its wings survived. That leads Borgonie and his colleagues to suggest that we need to widen our expectations as to where life might be found on other worlds.

“The ability of multicellular organisms to survive in the subsurface should be considered in the evolution of eukaryotes and the search for life on Mars,” he said.

Borgonie now believes that creatures like halicephalobus may well be found all over the world, including far below the ocean floor, where some scientists think Earth’s life originated.

“Harsh conditions do not automatically preclude complexity,” he said. “If life arose on Mars and it is still there deep underground, then it may have continued to evolve into something more complex than we are willing to entertain today.”