What do we know about life inside deep Earth?

This global research programme is supported by the Alfred P Sloan Foundation—a not-for-profit grant-making institution that supports research and education related to science, technology, engineering, mathematics and economics—and brings together more than 1,000 scientists from around the world to understand how the deep carbon cycles power our world. Biologists, physicists, geologists and a host of other scientists have been conducting experiments at approximately 100 field sites across the world for this. “We are in the final year of this decadal programme and we are now synthesizing all the big discoveries," says Marie Edmonds, a reader in earth sciences at the University of Cambridge who is responsible for the overall scientific and intellectual oversight of DCO’s synthesis and integration activities .

 DCO’s science and work is split into four theme-based communities: Extreme Physics and Chemistry (to understand the physical and chemical behaviour of carbon in extreme conditions), Deep Energy (to understand the volume and rates of abiogenic or inorganic hydrocarbons, and other organic species in the crust and mantle through geological time), Deep Life (to assess the nature and extent of the deep microbial and viral biosphere), and Reservoirs and Fluxes (to identify deep carbon reservoirs and determine how carbon moves among these reservoirs). The field studies conducted by these DCO communities have taken scientists all the way from Costa Rican volcanic sites to the Atlantis Massif, a 14,000ft-tall underwater mountain in the north Atlantic Ocean, in search of more analysis and answers. The results are fascinating. “We’ve discovered how carbon is stored in the deep Earth and lots of new forms of minerals and mineral structures in the deep Earth... We have a much greater understanding of how carbon is transferred into the deep Earth by a process called subduction," Edmonds explains on the phone.

Apart from serving on DCO’s executive committee, Edmonds also chairs DCO’s Synthesis Group 2019 (a subcommittee) and has served as the co-chair of the Reservoirs and Fluxes community since November 2014. “A big part of this programme is focused on using diamonds as windows into the interiors of the Earth. Many people think of diamonds as beautiful gem stones but DCO scientists have actually focused on their imperfection, i.e. the intrusions in the diamonds. They are actually windows into the geological past of our planet," she says.

Some of these findings and discoveries will have a bearing on scientific research and activities in the future. For example, DCO’s work in quantifying the carbon flux from volcanoes and other tectonic regions into the atmosphere to understand the time scale in which they operate. “We’ve realized that volcanic eruptions are preceded by rapid increases in CO2 flux and that raises the possibility of being able to forecast eruptions using the CO2 flux from volcanoes," says Edmonds. The research work is not restricted to establishing volcano monitoring systems across the world. DCO scientists have gone to the deepest depth of the oceans to collect sediments and rocks in search of other forms of life.

After drilling into the sea floor and sampling microbes from sites under continents and seas, DCO scientists constructed models of ecosystems that lie deep within our planet. In December, they revealed that the carbon mass stands at around 15-23 billion tonnes, which is “245-385 times greater than the carbon mass of all humans on the surface." Edmonds says the deep biosphere findings have direct implications for understanding life on other planets. “They have shown that the biological realm has got microbes that survive many kilometres deep in the oceanic crust in the sediments on the sea floor—environments that we never thought life was even possible," she adds. Clearly, we knew less about carbon than we thought.