The abundance of life on the Earth’s surface is mind blowing. Scientists have long known about the existence of a deep biosphere. Yet, estimating the mass and variety of life in the underground ecosystem – to several km depth – is even more difficult. This microscopic life plays a key role in controlling what happens on the surface, both on land and in the oceans, but it still escapes the known rules of life by seeking new ways to sustain itself and to survive.
About the project
The Deep Carbon Lab at the University of Bologna stems from the DeepSeep project, a European Research Council (ERC) grant that aims at answering a fundamental scientific question: what sustains life underground?
The main target of the DeepSeep project is the source of natural energy this hidden life needs, deep inside the Earth. This energy is similar to the ones we use in society, such as hydrogen and methane gases. However, it has a different and totally independent origin and forms tens of kilometers deep. This deep energy is not directly exploitable by humans, but could represent a fundamental source to feed microscopic life forms that inhabit the subsurface, the so-called deep biosphere. To investigate processes generating deep energy, we use rocks that have recorded what is happening at depth within the Earth. These rocks rise to the surface as a result of Earth’s movements (such as plate tectonics) and provide a window into the deep. Rocks are the key players of DeepSeep and hold information about parts of the Earth where humans can’t reach and can’t see.
Where do we work?
DeepSeep involves field sampling through expeditions in remote places where key rocks crop out of the Earth, laboratory analysis of the collected samples, and theoretical simulations.
Sampling locations across five continents, from Italy to Canada and Mongolia, are chosen on the basis of their geological characteristics well before getting in the field. These are places where the forces of plate tectonics have shuffled the Earth’s layers as a magician does with a pack of cards, bringing to the surface rocks that were once at the bottom of the pack.
How and why do we study rocks and minerals?
In the laboratory, our rock samples, collected during fieldwork, are cut into thin slices – so thin that they become transparent to light! They are placed under a microscope where light interferences produce colors characteristic of each mineral. It is here where the real work of the DeepSeep team begins.
The rocks we study contain microscopic bubbles of gas rich trapped inside minerals – we call them fluid inclusions, and they are proof that they formed deep inside the Earth. The fluid inclusions we study are rich in hydrogen and methane gas. These gases form from interactions between particular minerals, such as olivine (a olive-green-coloured magnesium- and iron-rich silicate), and fluids that stir within the rocks. These interactions generate new molecules, such as hydrogen and methane.
Olivine, as the most abundant mineral in the lithosphere (which comprises the Earth’s tectonic plates), is the focus of the DeepSeep project. The reaction between olivine and water, under certain conditions in the Earth, produces hydrogen and methane gas through the oxidation of iron, a component in olivine’s mineral structure. Hydrogen and methane are sources of energy for primitive microscopic life forms such as particular kinds of bacteria. Thus, rocks and water combined can create energy that life in the subsurface needs to survive.
By means of microscopic and chemical analyses, we study how and when these gases formed, and how effective they can be at feeding deep life in the darkest parts of the underground world.
Why is the DeepSeep project innovative?
Scientists have known for a long time that energy can be produced deep inside the Earth, but evidence supporting these ideas is still lacking because of the technical and financial difficulty in reaching such a great depth – under the roots of continents.
The DeepSeep project aims to break down this obstacle by exploiting Earth’s movements which has allowed rocks, once deep within the Earth, to emerge at the surface. We aim to learn from the Earth’s past to determine what might be needed for life to subsist in the present-day deep biosphere. There are several fields that the results we expect from this project can be applied to. They include: improving theories of how life originated on planet Earth and whether/how it might exist elsewhere; contributing to climate sciences through a stronger understanding of the deep carbon cycle; opening new windows for novel biotechnology studies based on hydrogen gas.
The team
DeepSeep is a multidisciplinary project. The core DeepSeep team includes members from five different countries who chose the Deep Carbon Lab at Bologna University as their research environment. The group consists entirely of geologists with different backgrounds and capable of unearthing clues from the subsurface in rocks. However, expeditions and research collaborations are often carried out with joint groups of experts in other fields, such as microbiologists and geodynamicists, that broaden the scope of the project.