Traces of Life on Earth Below World’s Deepest Point

Scientists have discovered potential evidence of life 10 kilometres below the sea floor in the Mariana Trench – the deepest part of the world’s oceans. 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.

Researchers ventured to Mariana Trench located in the western Pacific Ocean for this exploration.

That’s the implication from a new study that found signs of microbes alive today below the deepest place on Earth, the vast underwater canyon called the Mariana Trench.

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.

In the new study, published today in the Proceedings of the National Academy of Sciences, researchers sampled mineral-rich mud from the South Chamorro seamount, a mud volcano near the Mariana Trench fueled by the subduction zone below it. Though the team did not find intact microbes, they did discover tantalizing traces of organic material, which may add to evidence that life can survive in the most extreme of environments.

Picture of underwater ROV taking a sample

A remotely-operated vehicle prepares to take a sample from deep-sea hydrothermal vents. PHOTOGRAPH BY SCHMIDT OCEAN INSTITUTE

Life may be able to survive so deep because subduction zones are relatively cool; magma doesn’t hit the sinking crust until it reaches a lower point in the mantle. As such, Plümper extrapolated that the known temperature limit of life—around 250 degrees Fahrenheit—wouldn’t come until a depth of at least six miles below the ocean floor.

That could make these microbes the deepest life known on our planet, trumping microbes found in seafloor sediment as much as three miles down.

Picture of mineral

Serpentine is a class of minerals formed when olivine in the planet’s upper mantle reacts with water. PHOTOGRAPH BY DE AGOSTINI PICTURE LIBRARY, DE AGOSTINI, GETTY IMAGES

Mineral Power

The team examined organic material found in serpentine, a class of minerals formed when olivine in the upper mantle reacts with water pushed up from within the subduction zone. The combination produces hydrogen and methane gas, which microbes can use as food.

  • Such reactions produce methane gas and hydrogen, which could be used as a food source by microbes known as serpentinization, researchers said. Serpentine is pushed to the surface of the sea floor by hydrothermal vents, where the researchers found it.
  • Outside sources of organics were a concern during the study. Among other checks, the minerals tested negative for carbonate, which would form if seawater from closer to the surface had been in contact with water within the subduction zone.
  • They found trace amounts of organic material that was very similar to that produced by microbes living in more accessible places, the ‘’ reported. 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.

(Source: PNAS)

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