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.
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.
It is possible that the serpentine samples are evidence of life living far below the surface, researchers said.
The team used data from prior studies to calculate how far below the sea floor the serpentine was formed, which allowed them to estimate that the possible microbes might live - about ten kilometres below the sea floor.
The study was published in the journal Proceedings of the National Academy of Sciences.
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