We have learned that sunlight is a prerequisite for life on Earth. Photosynthetic organisms use sunlight to convert carbon dioxide into organic material that makes up the foundation of Earth’s food chains. Life in the porous rock material in the oceanic crust is fundamentally different. Energy — and therefore life’s driving force — derives from geochemical processes.

Now new findings suggest that this spatially vast ecosystem is largely supported by chemosynthesis.

There are small veins in the basaltic oceanic crust and water runs through them. The water probably reacts with reduced iron compounds, such as olivine, in the basalt and releases hydrogen. Microorganisms use the hydrogen as a source of energy to convert carbon dioxide into organic material.

Our Extended Biosphere

The oceanic crust covers 60 per cent of Earth’s surface. Taking the volume into consideration, this makes it the largest ecosystem on Earth. Since the 1970s, researchers have found local ecosystems, such as hot springs, which are sustained by chemical energy.

The hot springs are mainly found along the edges of the continental plates, where the newly formed oceanic crust meets seawater. However, the bulk of oceanic crust is deeply buried under layers of mud and hundreds to thousands of kilometres away from the geologically active areas on the edges of continental plates.

Even though this enormous ecosystem is probably mainly based on hydrogen, several different forms of life are found here. The hydrogen-oxidising microorganisms create organic material that forms the basis for other microorganisms in the basalt. Some organisms get their energy by producing methane or by reducing sulphate, while others get energy by breaking down organic carbon by means of fermentation.

Exploring the oceanic crust is still a young science. However, the prospects are great.

“Life in the deeply buried oceanic crust is supported by energy-sources that are fundamentally different from the ones that support life in both the mud layers in the sea bed and the oceanic water column. It is possible that life based on chemosynthesis is found on other planets, where the chemical environment permits. Our continued studies will hopefully reveal whether this is the case, and also what role life in the oceanic crust plays in the overall carbon cycle on our own planet,” says Dr Lever, the leader of the study.

Source(e):Sciencedaily

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