Life discovered in hot, deep ocean sediments

Fluorescence micrograph of deep subseafloor microbial cells
Fluorescence micrograph of deep subseafloor microbial cells detected at Site C0023

An international research team has discovered single-celled microorganisms where they didn’t expect.

Researchers have found organisms living in sediments 1,180 metres below the seabed at 120 degrees Celsius – way past the boiling point of water at the surface.

Sediments that lie deep below the ocean floor are harsh habitats. Temperature and pressure steadily increase with depth, while the energy supply becomes increasingly scarce. In spite of these conditions, microbial diversity below the seafloor is as rich as on Earth’s surface.

This research tells us that deep sediment is habitable in places that we did not think possible

URI Professor of Oceanography Arthur Spivack

Expedition 370 of the International Ocean Discovery Program drilled 1.2km into the Nankai Trough off the coast of Japan to find the extraordinary organisms. Marine sediments represent a massive microbial ecosystem, but we still do not fully understand what factors shape and limit life underneath the seafloor.

Deep-sea scientific vessel, 'Chinkyu' part of the work of Expedition 370 of the International Ocean Discovery Program.
IODP expedition 370 involved the scientific deep-sea drilling vessel Chikyu. Credit: JAMSTEC

With the deep biosphere so little understood, it brings up fundamental questions: Where are the limits of life – and so what might we find in outer space?

SOURCE 1, SOURCE 2

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