‘Worms from hell’ unearth possibilities for extraterrestrial life

Carl Pilcher, director of NASA’s Astrobiology Institute in California, said that the nematode discovery illustrates the usefulness of research on Earth for learning about possible extraterrestrial life.

“It is entirely plausible, in fact extremely likely, that subsurface environments like those described in these papers exist on other worlds in this solar system and in other planetary systems,” he said of the new work and Onstott’s earlier discoveries.

“We can now say that worlds with such subsurface environments could, in theory, harbor subsurface life, both microbial and multicellular,” Pilcher said. “That knowledge . . . can help guide us in developing missions and experiments to study other worlds.”

At least one of the bacteria species discovered earlier by Onstott and Lisa Pratt of Indiana University lives entirely disconnected from anything on the Earth’s surface or produced by photosynthesis. It uses the radioactive decay of nearby rocks as the energy source to break apart molecules that it then feeds on.

Borgonie speculates that the nematodes, which feed on bacteria, traveled through the cracks and crevices of rock in search of food. While they were determined to have lived deep underground for 3,000 to 10,000 years, the bacteria discovered by Onstott was found to have lived at its great depth between 3 million and 40 million years. A major difference between the two appears to be that while the nematodes adapted, the bacteria have evolved.

Complete worms, up to one-third of an inch in length, were found in two mines, and DNA of another was found in a third. They were found in water flowing from boreholes in the rock of the mines at depths from two-thirds of a mile to more than two miles. The worms nearer the surface were brought to a lab and survived, while the specimen at the deepest level was a DNA sample from a nematode but otherwise impossible to identify.

A primary hurdle the team had to overcome was proving that the nematodes had not come into the mines on the shoes or clothing of miners or through mine ventilation water. The contamination issue was resolved through extensive testing of the soil and mining water, which contains two disinfectant bleaches that would kill nematodes.

Borgonie, working with a team from South Africa’s University of the Free State in Bloemfontein, descended into the deep mines about 25 times to collect samples. He said there is good reason to believe nematodes, and other multi-celled organisms, also live deep below the surface of many other parts of the world, and especially below ocean beds.

Research into the distribution of underground microbes in recent decades has led scientists to conclude that more than half of the biological mass on Earth is below the surface.