The hidden world under the sea: Scientists find 'parallel universe' of life INSIDE the basalt of the oceanic crust

Scientists took core samples from crust hidden beneath 2.5km of water and hundreds of metres of sediment

They found evidence of micro-organisms living in the total absence of light and almost entirely disconnected from the world above

New discoveries about how such creatures survive in the extreme environment could help inform search for life on other planets



A parallel universe of life exists hidden beneath our planet's ocean floors and could help us search for life on other planets, new research claims.

An international team of scientists found evidence of tiny creatures living inside the basalt of the Pacific Ocean floor - covered by 2.5km of water and hundreds of metres of sediment.

The results of their studies, published today in the journal Science, have revealed evidence of a vast ecosystem whose characteristics are entirely different from any previously investigated.

The thundering waves of the Pacific Ocean: Scientists have found evidence of an ecosystem 2.5km beneath the surface of the ocean, actually inside the basalt of the Earth's crust

Core samples taken from the sea floor off the west coast of the U.S. contained traces of micro-organisms living in the total absence of light, and almost entirely disconnected from the world above.

'We're providing the first direct evidence of life in the deeply buried oceanic crust,' said microbiologist Mark Lever, who worked on the study as a PhD student at North Carolina.

'Our findings suggest that this spatially vast ecosystem is largely supported by chemosynthesis.'

It's widely held 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.

But life in the porous rock material in the oceanic crust is fundamentally different. Energy – and therefore life's driving force – derives from geochemical processes.

'There are small veins in the basaltic oceanic crust and water runs through them,' said Dr Lever, who is now a scientist at the Centre for Geomicrobiology at Aarhus University in Denmark.

'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.'

Dr Olivier Rouxel, of the French IFREMER institute, added: 'So far, evidence for life deep within oceanic crust was based on chemical and textural signatures in rocks, but direct proof was lacking.'

Evidence: Left, a cross section of a basalt core shows alteration halos surrounding veins or fractures. Right, a microscopic view shows pyrite granules with changes in sulphur concentration, an element used by microbes



The oceanic crust covers 60 per cent of the Earth's surface. Taking the volume into consideration, this makes it the largest ecosystem on Earth.

Since the Seventies, 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,' said Dr Lever.

'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.

'Until now, we've had no proof that there is life down there.'

Even though this enormous ecosystem is probably mainly hydrogen based, several different forms of life are found here, the researchers say. 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.

Dr Lever is a specialist in sulphur-reducing and methane-producing organisms, and these were the organisms he also chose to examine among the samples taken from the oceanic crust.

These organisms are able to use hydrogen as a source of energy, and are typically not found in seawater.

This map shows the locations off America's Pacific west coast, where researchers took their core samples

Dr Lever had to make sure that no microorganisms had been introduced as contaminants during the drilling process, or transported from bottom seawater entering the basaltic veins.

'We collected rock samples 55km from the nearest outcrop where seawater is entering the basalt,' he explained.

'Here the water in the basaltic veins has a chemical composition that differs fundamentally from seawater, for instance, it is devoid of oxygen produced by photosynthesis.

'The microorganisms we found are native to basalt.'

Dr Lever's basalt is 3.5million years old, but laboratory cultures show that the DNA belonging to these organisms is not fossil.

'It all began when I extracted DNA from the rock samples we had brought up,' he said. 'To my great surprise, I identified genes that are found in methane-producing microorganisms.

'We subsequently analysed the chemical signatures in the rock material, and our work with carbon isotopes provided clear evidence that the organic material did not derive from dead plankton introduced by seawater, but was formed within the oceanic crust.

'In addition, sulphur isotopes showed us that microbial cycling of sulphur had taken place in the same rocks.

'These could all have been fossil signatures of life, but we cultured microorganisms from basalt rocks in the laboratory and were able to measure microbial methane production.'

Mark Lever of Aarhus University works under sterile conditions in the laboratory: Familiar tools such as a hammer are necessary for a geomicrobiologist working with rock samples from the oceanic crust.

Dr Jeff Alt of the University of Michigan at Ann Arbor added: 'Our work proves that microbes play an important role in basalt chemistry, and thereby influence ocean chemistry'.

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,' said Dr Lever.

'It is possible that life based on chemosynthesis is found on other planets, where the chemical environment permits.