Earth in Five Reactions

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Earth in Five Reactions

Ever wonder what the most important reaction on Earth might be?  This question was posed at a DCO Synthesis Planning Workshop at the University of Rhode Island in October 2015.  As one might expect, a lively and spirited discussion ensued. But the exchange illustrated a general lack of consensus among scientists about the key reactions that govern the transformation and movement of carbon in Earth.This fundamental question to identify the key drivers of deep carbon science inspired the “Earth in Five Reactions” (“5R”) synthesis project.
The 5R project intends to identify and use the five most important reactions as the central themes to synthesize and disseminate deep carbon knowledge and findings, while providing a new and integrative perspective for scientists to understand and advance deep carbon science. The effort will have ancillary benefits. By organizing DCO’s abundant and disparate discoveries into a coherent structure, the program-wide 5R synthesis project has the potential to motivate and guide future research by helping scientists identify data gaps in understanding and information needing to be refined.  It also has the potential to establish new frontiers for scientific exploration and investigation.

Serpentinization a is a key Earth process along plate boundaries and the sea floor. This sample of serpentinite is from the collection of the Department of Geology and Paleontology at Comenius University, Bratislava. Credit: Ondrej Pelech, Slovak Geological Survey

Involving the Scientific Community
The 5R project consists of multiple phases, each one building upon the previous. The process launched with a community poll to solicit opinions on selection criteria and candidates for the five most important reactions that integrate deep carbon science. Principal Investigators Jie (Jackie) Li and Simon Redfern polled scientists in person at the Third DCO International Science Meeting in St. Andrews, Scotland in March 2017. The results of this initial poll are serving as the basis for a larger poll, which is being conducted by personal email to each of the ~1,000 members of DCO’s Science Network.
After receiving input from DCO's Science Network, the project leaders plan to solicit input from non-DCO researchers in the broader community of Earth science by conducting surveys through mailing lists and newsletters of relevant organizations such as the American Geophysical Union and the Geochemical Society. They also will encourage contributions from the public through social media sites such as Twitter and Reddit.  
The poll is designed to introduce the “five reactions” synthesis initiative and collect input on how to evaluate the importance of a reaction in governing the Earth’s deep carbon cycle. Some critical reactions may have stretched over an extended (or even currently uncertain) time scale (e.g., inner core formation, extending back between 500 million years and more than four billion years, depending on which values of heat flow are considered), whereas others may be widespread spatially and occur under broad ranges of pressure and temperature (for example, redox reactions in solids and liquids). The energetics of a reaction also may be important. Other important planetary reactions may involve dominant carbon-bearing species and other complex reactions that may tie many carbon-bearing species together. Unique reactions that can be used as indicators, tracers, or diagnostic tools for carbon cycling are other possible targets of interest.
The poll consists of three tiers of questions. Respondents who complete all three tiers will be considered for the opportunity to participate in a 5R workshop in Washington, DC, in March 2018. Workshop participants will use the survey responses to arrive at a consensus, and develop a plan for sharing key advances in deep carbon science with the scientific community and broader audiences using the framework of the top five reactions. Following the workshop, a special issue will highlight the scientific products, in addition to multi-media educational resources.
Expected output
Following the workshop, a special issue will highlight the scientific products, in addition to multi-media educational resources. The theme of the special issue will be “Earth in five reactions – a deep carbon perspective.” It will present a big picture view that integrates the discoveries of the four DCO Communities over the preceding decade, what they have learned about the role of carbon in planetary function and how the five reactions are an integral part of how carbon is stored and cycled in Earth.
Another expected output of the 5R synthesis project is the creation of electronic resources that explain the Earth’s deep carbon in five reactions in accessible terms geared to non-expert audiences. These resources could range from printable posters to downloadable PowerPoint slides to info graphics that could be used in K-12 classes, for example, so, students can learn to recognize and classify the five types of chemical reactions that are most important to planetary function and deep carbon. All will be designed so they can be shared digitally to help maximize distribution to interested audiences. By borrowing the familiar term “five reactions,” the team expects to offer appealing and accessible media to enhance public knowledge and appreciation of deep carbon science, and integration of it into understanding of how Earth works. (Jackie) Li) and Redfern) are co-PIs for Earth in Five Reactions. Li is an experimental geochemist and mineral physicist who has spent more than two decades studying material properties at extreme pressures and temperatures and investigating the thermal and chemical evolution history of the Earth and other terrestrial planetary bodies. Her research encompasses a wide spectrum of deep-carbon issues and has tested the hypothesis of hidden carbon in the Earth’s inner core, evaluated carbon distribution during core formation, proposed models involving iron-carbon melt to explain anomalous seismic signals at the Earth’s core-mantle boundary, assessed the fate of subducted carbon in the Earth’s transition, and traced the delivery of carbon from proto-planetary disc to Earth’s surface as an ingredient for life. She is a member of DCO’s Extreme Physics and Chemistry Science Community.

Redfern is a mineral scientist with over 25 years research experience. The author of more than 240 peer reviewed papers (H-index 42), he has worked on a broad range of deep carbon-related research, including the behavior of carbonate minerals in the deep Earth, the biomineralization processes associated with biogenic carbonates in marine organisms (foraminifera), the role of aqueous solutions at deep Earth conditions in transporting or precipitating deep carbon, and the use of diamonds as laboratory tools for the study of materials at extreme conditions. Redfern has acted as journal editor for American Mineralogist, Mineralogical Magazine, and (currently) Frontiers in Earth Sciences: Earth and Planetary Materials, and has spent time as a British Science Association Media Fellow.
An example reaction
Redox reactions involving carbon-bearing species with variable valence state are but one example of reactions that are of interest to different communities within DCO. A search of the DCO’s publication portal resulted in 23 scholarly articles about these reactions. Redox reactions were found to influence melting in the Earth’s mantle (e.g., Litasov 2011; Dasgupta and Hirschmann 2010; Extreme Physics and Chemistry), volcanism and diamond formation (e.g., Cottrell and Kelley 2013; Sverjensky and Huang 2015; Reservoirs and Fluxes), the behavior of microbial communities (e.g., Felden et al. 2014; Contreras et al. 2013, Deep Life), and the abiogenic production of hydrocarbons (e.g., Andeani et al. 2013; Debret et al. 2014; Deep Energy). Some cross-community research projects have also been carried out to investigate the stability of glutamic acid in hydrothermal fluids (e.g., Namhey et al. 2014, Secretariat).
Given the prevalence of redox reactions in geological and biological processes, 23 articles may appear rather few. Indeed, many more articles on the DCO publication list involve a redox reaction as a key process but are not retrieved readily by the search. For instance, redox evolution often occurs during serpentinization, a geological process through which mafic and ultramafic rocks react with water to form serpentinite. In the presence of iron, serpentinization may produce hydrogen and form methane, thus profoundly influencing the deep carbon cycle (e.g., McCollom and Seewald 2013; Crespo-Medina et al. 2014). Searching for “serpentinization’ on the same site returned 83 articles. The idea is that through the 5R synthesis process, most, if not all, of the DCO findings in which redox reaction plays a crucial role could be identified, providing insights into its contribution and influence over the deep carbon cycle.



7 September 2017
Darlene Trew Crist, Synthesis Group 2019 manager

Last chance for input!  Close to 100 respondents have completed the Earth in Five Reactions Survey. Project leaders are about to select participants for the all-expense paid workshop to decide on the five most important reactions in Washington, DC in March 2018. If you haven't completed your survey, please do so today to be considered for the workshop. Simply click here to complete it.

13 June 2017
Darlene Trew Crist, Synthesis Group 2019 manager


Earth in Five Reactions project leaders Jackie Li and Simon Redfern have drafted a survey to elicit input from the DCO Science Network about the five most important carbon reactions on Earth. The survey was launched at the Third DCO International Science meeting in St. Andrews, Scotland on 23 March 2017.
The opinions of all members of DCO's Science Network are now being sought. Please complete the survey, by clicking here. The survey consists of three tiers of questions.  Respondents who complete all three tiers of the survey will be considered for the opportunity to participate in a 5R workshop in Washington, DC, in March 2018. 
We look forward to your input!

Further Reading

Andreani, M., Muñoz, Marcaillou, C., Delacour, A., 2013. μXANES study of iron redox state in serpentine during oceanic serpentinization, Lithos, 178, 70-83

Chen, B., Z., L., Zhang, D., Liu, J., Hu, M.Y., Zhao, J., Bi, W., Alp, E.E., Xiao, Y., Chow, P., Li, J., 2014. Hidden carbon in Earth's inner core revealed by shear softening in dense Fe7C3. Proc. Natl. Acad. Sci. USA 111, 17755-17758.

Contreras, S., Meister, P., Liu, B., Prieto-Mollar, X., Hinrichs, K.-U., Khanlili, A., Ferdelman, T. G., Kuypers, M. M. M., Jørgensen, B. B., 2013. Cyclic 100-ka (glacial-interglacial) migration of subseafloor redox zonation on the Peruvian shelf, Proc. Natl. Acad. Sci. USA. 110(45), 18098-18103

Cottrell, E., Kelly, K.A., 2013. Redox heterogeneity in mid-ocean ridge basalts as a function of mantle source. Science 340, 1314-1317.

Litasov, K., 2011. Physicochemical conditions for melting in the Earth’s mantle containing a C– O–H fluid (from experimental data). Russ. Geol. Geophys. 52, 475-492.

Dasgupta, R., Hirschmann, M.M., 2010. The deep carbon cycle and melting in Earth’s Interior. Earth Planet. Sci. Lett. 298, 1-13.

Debret, B., Andreani, M, Muñoz, M., Bolfan-Casanova, N., Carlut, J., Nicollet, C., Schwartz, S., Trcera, N., 2014. Evolution of Fe redox state in serpentine during subduction, Earth Planet. Sci. Lett., 400, 206-218

Felden, J., Ruff, S.E., Ertefai, T., Inagaki, F., Hinrichs, K. –U., Wenzhöfer, F., 2014. Anaerobic methanotrophic community of a 5346-m-deep vesicomyid clam colony in the Japan Trench, Geobiology, 12(3), 183-199


Kelemen, P., B., Matter, J., 2008. In situ carbonation of peridotite for CO2 storage. Proc. Natl. Acad. Sci. USA 105, 17295-17300.

McCollom, T.M., and Seewald, J.S., 2013. Serpentinites, hydrogens, and life, Elements DOI: 10.2113/gselements.9.2.129

Namhey, L., Dionysis, I. F., Sverjensky, D., Cody, G., Hazen, R. M., 2014. The effects of temperature, pH and redox state on the stability of glutamic acid in hydrothermal fluids, Geochim. Cosmochim. Acta, 135, 66-86

Pearson, D.G., Brenker, F.E., Nestola, F., McNeill, J., Nasdala, L., Hutchison, M.T., Matveev, S., Mather, K., Silversmit, G., Schmitz, S., Vekemans, B., Vincze, L., 2014. Hydrous mantle transition zone indicated by ringwoodite included within diamond. Nature 507, 221-224.

Sverjensky, D., Huang, F., 2015. Diamond formation due to a pH drop during fluid–rock interactions. Nat. Commun., DOI: 10.1038/ncomms9702