“Knowledge of Deep Carbon Makes a Giant Leap”
This year, the Deep Carbon Observatory will be ten years old. Geologist Isabelle Daniel, a member of the coordinating team, reviews this active international project to study the carbon cycle under the surface of the earth and discover the abundant life that lives up to 5 km below the surface of the continents.
Photo © Elisabeth Rull / Divergence Image
At the end of 2010, an email and then a telephone conversation with one of the founders of the Deep Carbon Observatory (DCO) in the United States, brought Isabelle Daniel to this decade’s leading geology project. Its goal? To study carbon, the chemical backbone of life, in all its forms, in the depths of the earth. Surprisingly, remarkably little is known about it. Several things led this renowned mineralogist, currently director of the Lyon Observatory and vice-president of the European Mineralogical Union to be invited: her curiosity in fields of research different to her own, already wide, as she looks at the interactions between minerals, fluids and microorganisms. And her desire to test a method of project management that differs considerably from what is practiced in France. Nine years later, her enthusiasm is even stronger thanks to this multidisciplinary adventure, rich in scientific results and human encounters.
La Recherche • How was the Deep Carbon Observatory born?
Isabelle Daniel • On the initiative of Robert Hazen, a mineralogist and astrobiologist at the geophysics laboratory at the Carnegie Institution, in Washington, with the support of Russell Hemley, director of this laboratory. In 2007, Robert Hazen gave a conference at the New York Century Club on his favourite topic: the origins of life and the role minerals played in the appearance of the first biological molecules. Jesse Ausubel, a representative from the Sloan Foundation, an important American organisation that supports scientific and technological research, was in the audience. The foundation was looking to fund new projects and Robert Hazen’s presentation piqued Jesse Ausubel’s interest. After thinking about starting a programme on the origins of life, they ultimately decided to go with a similar but far less popular theme: deep carbon, this unique element that makes up most of life as we know it. In May 2008, the foundation and the Carnegie Institution organised a three-day meeting with a hundred or so scientists from various horizons, to explore the possibilities and identify the key issues and challenges. The project was officially launched in August 2009!
The idea emerged in the United States, but this is an international project. When did you join it?
From the beginning, when I had the pleasure of being invited to the May 2008 meeting. In the States, when a foundation wants to start a project, they invite a selection of scientists, chosen for their skills and also for their personality, to debate. At the end of 2010, the project founders asked me to manage one of the project areas. At the time, I was working on experimental simulation of microbial behaviour at great depths, under extreme conditions of pressure and temperature. It was quite new and the fact of studying the interactions between minerals, fluids and microorganisms was proof of my interest in varied disciplines. This wide spectrum interested them, and I was asked to be part of the executive committee, as well as to coordinate one of the parts. That was ten years ago. At only 40 years of age, I felt a little out of my depth! But I thought the project was exciting and it was an opportunity to work in a very different context from what I was used to, with the appeal of interdisciplinarity. So I went for it.
What major challenges were identified in 2008?
Data about the carbon cycle on the surface were numerous, in particular concerning emissions and carbon sinks, thanks to research into climate change. Data about the deep carbon cycle were sketchy. For example, we did not know the quantity of carbon present inside the Earth, the forms in which it was found, and its distribution between the crust, mantle and the core. These questions gave rise to the first major topic, Extreme Physics and Chemistry. The question also arose of the extension of life in deep or dark environments, either under the continents or in the ocean floor. We wanted to know which organisms were living there and how they interacted with their rocky environment. A community of Deep Life scientists that I coordinated from 2009 to 2013, was formed on this topic. First, they used an approach combining experimentation and modelling. Then, from 2011, they focused on conducting the Census of Deep Life (see inset).
What are the two other DCO topics?
The Reservoirs and Fluxes community looks mainly at the carbon cycle around subduction zones, the emission of carbon from oceanic ridges and the diffuse carbon flows outside major orogenic belts (*). It also includes a smaller group studying diamonds and how they form. The fourth community that I coordinate with David Cole from Ohio State University and more recently with Edward Young from the California University in Los Angeles, is called Deep Energy and was originally linked to the Extreme Physics and Chemistry community. After a year, we realised that we were studying quite different things, so we decided to separate them. Deep Energy looks more at the content and origin (biological or not) of hydrogen and methane in subsurface conditions, up to a few kilometres in depth. It still has a strong interdisciplinary aspect as we cross-reference observations from the natural environment with laboratory experiments and numerical simulation.
You insist a lot on the interdisciplinary nature of the project.
Yes, and on the important of meeting people who on the face of it, are not used to working together because of their centres of interest. This brings up questions that nobody would necessarily have asked alone. This way of organising projects, based mainly on the interactions between people and on the trust granted to each partner, is far more open than the administratively heavy, fixed-term projects, usually conducted by national agencies. It gives you the intellectual freedom to make discoveries.
If you could only mention one of the significant results, what would it be?
The choice is difficult. In 2014, there was a discovery, in an ultra-deep diamond, of a mineral inclusion, ringwoodite, containing 1.4% water by weight. This means that water is present in the place this diamond formed, in the transition zone between the upper and lower mantels, located between 410 and 660 km deep. It was suspected from seismological and petrological models. Now we have the proof! Another significant result, in terms of the internal structure of the earth, concerns the distribution of carbon in the depths, of which we knew almost nothing. We now have converging elements indicating that two thirds of the earth’s carbon could be in the core, in the form of iron carbide (Fe7C3), and even that there is a large proportion in the inner core, the solid part of the core (see here and here). In a different domain, I also like a result from the Reservoirs and Fluxes community, showing that CO2 emissions are five to ten times greater a few weeks prior to major volcanic eruptions. Of course, it’s not from a few days beforehand, as we would like it to be in order to evacuate populations. But I think it’s very important to show that we have precursors to these big eruptions. It was made partially possible by volcanic instruments developed for numerous DCO volcanology campaigns.
Recently, the DCO also managed to quantify the deep biosphere…
Yes, as part of the Census of Deep Life, focused on by the Deep Life community from 2011. By collecting all the analyses of samples taken by drilling at various places on the planet, Cara Magnabosco from the Flatiron Institute in New York and nine colleagues from various laboratories compiled a large database. With this and models they quantified the deep biosphere in the temperature zone where we believe life is possible (less than 122°C). According to their estimates, there are 2 to 6 x 10 power 29 cells under the continents and 5 x 10 power 29 cells under the oceans. In total, that makes 7 to 11 x 10 power 29 cells in the depths of the earth. This represents 15 to 23 billion tonnes of carbon, or twice the amount from surface microorganisms!
How did the DCO make this type of discovery?
For deep life, the winds were in our favour; we arrived at a time when we had both the ability to get samples from deeper and deeper zone, thanks to increasingly efficient drilling equipment, to analyse these samples where the cells are rare and to analyse the data obtained using big data methods. The DCO was able to take full advantage of this situation on several levels. Firstly, they facilitated data collection in new environments, by backing the work of small groups all around the world, and by supporting major drilling campaigns conducted as part of two pre-existing programmes: the Integrated Ocean Drilling Program and the International Continental Drilling Program. It also backed the massive sequencing of samples, mainly done at the Woods Hole Marine Biology Laboratory in the United States, under the responsibility of Mitch Sogin. Moreover, the extent of the DCO opened doors that would otherwise have remained shut. For example, for the work on diamonds, it fostered ties with the renowned international diamond producer De Beers, and with the Gemmological Institute of America, accessing their collections of diamonds, unimaginable at an individual level.
Does this type of project also lead to the development of new technologies?
Yes, it means we can find the funding needed to design and manufacture machines which, without its support, would never have seen the light of day. For example, to decrypt the biological or non-biological origin of methane, we needed a mass spectrometer that could not only detect isotopes of carbon and hydrogen that make up methane, but also quantify them, as their proportions indicate the origin and the temperature at which the methane forms. The backing of the DCO meant that a whole network of scientists could provide samples over the long term and that the machine had good visibility. This facilitated funding by other partners – the DCO only provided 10% of the several million dollars necessary. For the British company that made it, Nu Instrument, it was also the assurance that the adventure would be worth it. This unique spectrometer, called Panorama, has been installed in California University in Los Angeles since March 2015. Since then, it has shown that almost all natural methane samples are of biological origin. Its spectacular resolution has also provided access to the metabolic processes that produce this methane.
Is a second DCO envisaged?
No, that is not the intention of the Sloan Foundation which believes ten years is enough. This is true! So the DCO as we know it will cease to exist. However, the collaborations that have built up over these ten years will continue, especially with the young scientists. Many of them took part in the project as it is the policy of the Sloan Foundation to support them. As a result, there is now an extremely dynamic community of young researchers, used to and comfortable working in an interdisciplinary fashion. When we speak about the results of the DCO, we tend to talk about scientific results and technological progress. But in my eyes, this community is just as much of a success!
(*) An orogenic belt is an area in which mountains are formed.
THE UNSUSPECTED RICHNESS OF LIFE IN THE DEPTHS
Samples have been taken from 2.5 km under the ocean floor and 5 km under the continents, in hydrothermal vents, old mines, under volcanoes or deep in the heart of aquifers. They have been examined under the microscope and genetically sequenced. Verdict? Life is indeed present and very diverse. Mostly comprised of prokaryotes (bacteria and archae), this biosphere also contains eukaryotes, or multicellular organisms. Microscopic nematodes such as Poikilolaimus have been discovered, curled up in the pores of rocks in a South-African gold mine, 1.5 km deep. Without the sun for energy, all these organisms use chemosynthesis, a process in which they synthesize organic molecules using the energy taken from mineral compounds rather than from sunlight. Their quantity and metabolic activity usually fall when the depth increases, but with some abundance in areas where energy can be extracted. Also, generally speaking, the communities described in a specific place are complex and intrinsically varied in terms of species. However, the types and families are similar whatever the environment or geographical area considered, which intrigues researchers no end. (Image : this small nematode worm lives 1.4 km beneath the surface in the rock pores, photo © Extreme Life Isyensya / Gaëtan Borgoni).
> INTERVIEWEE
Isabelle Daniel
Mineralogist and geologist, Isabelle Daniel, who is part of the executive committee of the Deep Carbon Observatory, is director of the Observatoire de Lyon.
1991 • Isabelle Daniel obtained her teaching degree in the Life and Earth Sciences.
1995 • Got her Ph.D. in Earth Sciences from the Claude-Bernard Lyon 1 University.
1996 • Lyon 1 University hired her as a lecturer; she worked on experimentation in extreme conditions in the earth’s mantle.
2004 • Became a professor, also at Lyon 1; her research concerned the interactions between fluids and rocks under extreme conditions.
2008-2013 • Became a junior member of the Institut Universitaire de France.
2010 • Joined the Executive Committee of the Deep Carbon Observatory.
2015 • Appointed director of the Observatoire des Sciences de l'Univers in Lyon.m
