Deep drilling off the American Pacific coast has finally proven that life exists beneath oceanic crust.
The findings were reported in the International Weekly Science Journal.
A team of scientists made the discovery by drilling 600 metres into seafloor sediment and then going a further 2.5 km down into underlying basaltic oceanic crust.
The results of the study could reveal the largest ecosystem on the planet as 70% of the Earth's crust lies below sea level.
“There are small veins in the basaltic oceanic crust and water runs through them" said lead study author postdoc Mark Lever, of Aarhus University’s Department of Bioscience in a release.
"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".
The theory that life existed in oceanic crust has been around since the 1800's and recent studies looked at hydrothermal vents along ocean ridges.
The issue of proving life existed was always difficult because most of the ocean's crust is deep under layers of mud, rock, and sediment.
New drill technology allowed scientists to get to the depths required, drilling on the eastern flank of the Juan de Fuca Ridge.
To ensure that the organisms found were native to the basalt and not transported there by seawater, drilling was performed 55 kilometres away from the nearest ridge that could contaminate results.
The findings are significant because most life on Earth derives energy from sunlight but these organisms use geochemical processes involving carbon dioxide - also known as chemosynthesis.
Researchers hope to use the findings to see if life based on chemosynthesis could exist on other planets.