Magazine article Oceanus

Mummified Microbes: Life Thrives in Niches Deep below the Seafloor

Magazine article Oceanus

Mummified Microbes: Life Thrives in Niches Deep below the Seafloor

Article excerpt

Scientists have found evidence that microbes can thrive deep below the seafloor--sustained by chemicals produced by reactions between seawater and rocks in Earth's mantle.

It's difficult to gain direct access to the mantle, but a team led by Woods Hole Oceanographic Institution scientist Frieder Klein analyzed samples of ancient mantle rocks that had been thrust up from Earths interior toward the seafloor. The scientists found lipids, amino acids, and proteins of mummified microbes that were preserved and encased in tiny pockets in the rocks.

Fueling this life in the mantle--then and presumably still--is a confluence of chemical conditions that begins when seawater percolates through fractures in the seafloor. The water gets heated along the way. When it encounters a type of rock in Earth's mantle called peridotite, it reacts with minerals in peridotite and generates hydrogen, methane, and other gases. The seawater is chemically altered into hot hydrothermal fluids, which rise buoyantly toward the surface. When hydrothermal fluids mix again with seawater, together they provide a banquet of energy- and nutrient-supplying chemical compounds for microbes such as bacteria and archaea.

"All the chemical ingredients necessary to support life and drive these ecosystems came from inorganic materials: seawater and rock," Klein said. "Colonies of bacteria and archaea feeding off these chemicals became engulfed in the minerals in the fractured rock. This kept them completely isolated from the environment. …

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