Signs of life found below world's deepest point

Scientists have discovered potential evidence of life ten kilometres below the sea floor in the Mariana Trench - the deepest part of the world's oceans.

The trench is part of a subduction zone, where the Pacific tectonic plate slips beneath the Philippine Sea plate. The surrounding seafloor is littered with hydrothermal vents and mud volcanoes, churning out ingredients from the deep Earth. Researchers, including those from Utrecht University in the Netherlands, ventured to Mariana Trench located in the western Pacific Ocean. They used Remotely Operated Vehicles (ROV) to extract about 46 samples of serpentine from the ocean floor near the South Chamorro mud volcano, which they brought back to their lab for study. "This is another hint at a great, deep biosphere on our planet," says study leader Oliver Plümper, a researcher at the Netherlands' Utrecht University. "It could be huge or very small, but there is definitely something going on that we don't understand yet." Serpentine is a mineral that forms when olivine in the upper mantle meets water pushed up from a subduction zone, researchers said.

Such reactions produce methane gas and hydrogen, which could be used as a food source by microbes, researchers said.

Serpentine is pushed to the surface of the sea floor by hydrothermal vents, where the researchers found it.

They found trace amounts of organic material that was very similar to that produced by microbes living in more accessible places, the 'Phys.org' reported. It is possible that the serpentine samples are evidence of life living far below the surface, researchers said.

It is also possible that the organic material was produced without help from biology at all, in a natural version of the process humans use to make synthetic oil and fuel. However, this alternate possibility would still be an exciting one, according to the research team.

"If it can do that, it is amazing in itself," says Plümper, who notes that the mud volcanoes where the serpentine formed are thought to have existed when life on Earth got its start. "Then we know that geologic process can create complex organic molecules."

The team used data from prior studies to calculate how far below the sea floor the serpentine was formed. The study was published in the journal Proceedings of the National Academy of Sciences.