Global expedition discovers mantle rocks with signs of life

An international team of scientists has collected an unprecedented sequence of rock samples from the shallow mantle of the ocean crust that bear signs of life, unique carbon cycling and ocean crust movement.

The 32-member team that recently returned from a 47-day research expedition to the middle of the Atlantic Ocean collected these unique rock samples using seabed rock drills from Germany and Britain.

This is the first time in the history of the decades-long scientific ocean drilling programme that such technology has been utilised.

"We will also gain valuable insight into how these rocks react with circulating seawater at the seafloor and its consequences for chemical cycles and life," said expedition co-chief scientist Gretchen Früh-Green from ETH Zurich, Switzerland, in a statement.

The aims of the expedition are to determine how mantle rocks are brought to the seafloor and react with seawater.

Such reactions may fuel life in the absence of sunlight which may be how life developed early in Earth's history, or on other planets.

The team that included Dr Beth Orcutt from Bigelow Laboratory for Ocean Sciences in the US also hopes to learn more about what happens to carbon during the reactions between the rocks and the seawater - processes that could impact on climate by sequestering carbon.

"During drilling, we found evidence for hydrogen and methane in our samples, which microbes can 'eat' to grow and form new cells," explained Dr Orcutt.

Similar rocks and gases are found on other planets "so by studying how life exists in such harsh conditions deep below the seafloor, we inform the search for life elsewhere in the Universe", he added.

The scientists are part of the International Ocean Discovery Program (IODP) Expedition 357, conducted by the European Consortium for Ocean Research Drilling (ECORD) as part of the IODP.

The rock cores were collected from Atlantis Massif, a 4,000-metre tall underwater mountain along the Mid-Atlantic Ridge.

The rock drills were equipped with new technologies to enable the scientists to detect signs of life in the rock samples.