"I'm not surprised," said Julie Huber, an oceanographer at the Marine Biological Laboratory in Massachusetts who wasn't involved in the study. "There's barely a place in the world that doesn't hold life."
Scientists at the Japan Agency for Marine-earth Science and Technology found the microbes by drilling off the Shimokita Peninsula in Northern Japan. Remarkably, they seem to have more in common at the genetic level with life found in terrestrial soil than that found in the marine seabed.
Scientists say their home — most likely the ancient wetlands of Japan — was pushed underground more than 20 million years ago, creating layers of coal deposit under the ocean and becoming an extension of the ocean's vast and extremely diverse biome. The trapped microbes have survived in the environment for ages, and scientists say the discovery could provide a unique window to what terrestrial life was like all that time ago.
The life forms are not abundant, and their metabolisms run at very low levels. Still, they are alive and well, surviving on powdered coal and hydrogen and pumping out methane, the signature molecule leftover by life in extreme environments. They belong to the less commonly known domain of life called Archaea, home also to the extremophiles living in volcanic hot springs and deep sea hydrothermal vents.
"They're kind of just really cool bugs," Huber said. "They are very successful organisms."
There are still a number of questions left to answer. Have these new microbes changed over the course of time? Have they adapted or branched off into new species? Or have they always been the same critter just barely eking by?
This is the deepest investigation ever into life in the sub-seafloor. Most earlier studies focused on easy-to-reach marine sediments, but the microbes collected there were found to be distinct from the new, deeper forms.
To collect information on life forms deep under the floor requires advanced technology and techniques to ensure the samples are free from contamination — that is, to make sure microbes are actually from the place they're being pulled.
Scientists found cells of the microbes in every sample they took in the 8,090 feet-tall column drilled into the ocean floor. They were most abundant in samples from coal deposits, which provide the main source of energy needed to support life.