Earth in Five Reactions

Defining Earth's Most Important Reactions

Earth in Five ReactionsEver 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” (“E5R”) synthesis project.

The E5R project has identified and is using the five most important reactions as the central themes to synthesize and disseminate deep carbon knowledge and findings, providing a new and integrative perspective for scientists to understand and advance deep carbon science. By organizing DCO’s abundant and disparate discoveries into a coherent structure, the program-wide E5R 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.

What Makes Earth Habitable?

E5R Postcard
These reactions were selected for their roles in making Earth a unique planet with an oxygenated atmosphere and an abundant array of life. Click to download this postcard with the key printed on the back. Credit DCO/Josh Wood.

Deep Carbon Observatory polled its community members about what they considered the five most important carbon-related reactions on Earth. After lively and sometime contentious debate, these reactions were selected for their roles in making Earth a unique planet with an oxygenated atmosphere and an abundant array of life. All of the following drive some aspect of the deep carbon cycle. 

1. Hydrogenation | Dehydrogenation
CH4 + 2H2O ⇌ CO2 + 4H2
Nature’s battery: this reaction may have powered Earth’s first life forms. In cow intestines, it paves the way for methane formation.

2. Carboxylation | Decarboxylation
6CO2 + 6H2O ⇌ C6H12O6 + 6O2
Without this reaction, we would have neither oxygen to breathe nor food to eat. Photosynthesis is an example of a carboxylation cycle.

3. Carbonation | Decarbonation
CO2 + CaSiO3 ⇌ CaCO3 + SiO2
Processes occurring at Earth’s surface, like weathering, modulate the amount of carbon in the atmosphere and help maintain a temperature range suitable for life.

4. Carbon dioxide dissolution | Outgassing
CO2(aq) ⇌ CO2(g)
Through this reaction, Earth’s volcanoes release carbon dioxide, like bubbles in a bottle of champagne, balancing the deep carbon cycle.

5. Hydration | Dehydration
H2O + CO2 ⇌ H2CO3
CO2 + 18Mg2SiO4 + 6Fe2SiO4 + 26H2O ⇌ CH4 + 12Mg3Si2O5(OH)4 + 4Fe3O4
One example of this reaction at work is ocean acidification. The ocean takes up carbon dioxide from the atmosphere, threatening marine life by making it harder for organisms like corals to build their skeletons.


Redox freezing | Melting
MgCO3 + 2Fe ⇌ C + 3(Fe2/3Mg1/3)O

Metal silicate reaction
C(metal) + 2FeO(silicate) ⇌ CO2(silicate) + 2Fe(metal)

Metal freezing | Melting
FeCx(l) ⇌ FeCy(l) + Fe7C3, where y<x


Sharing E5R

Deep Earth Haiku
Deep Earth Haiku gives visitors a chance to post their own poetry about deep Earth.

The Engagement Team is working with the E5R editorial team to develop a suite of resources that explain the Earth’s deep carbon in five reactions geared to a variety of audiences through a number of channels. Audiences range from scientific peers to interested non-experts, and they will be reached through publications, social media, and at conferences and events. The discussions, exercises, and debates at the 2018 E5R Workshop helped to spark many of the ideas listed below.

Underway or completed

  • Webinar – Transforming planetary perceptions: Earth in Five Reactions
    The Earth in Five Reactions project leaders Jackie Li, Simon Redfern, and Donato Giovannelli, along with project participant Jennifer Glass, share how carbon plays a central role in making Earth habitable.
  • Deep Earth Haiku
    Earth in Five Reactions researchers are using haiku to express key themes about Earth's essential reactions to the scientific community and the public. This web app allows everyone to contribute their own deep Earth haiku.
  • 2018 AGU Tutorial TalkEarth in Five Reactions: What Makes Our Planet Unique in the Solar System? 
    Jie Li (University of Michigan Ann Arbor, USA), Simon A T Redfern (University of Cambridge, UK), Marie Edmond (University of Cambridge, UK), Donato Giovannelli (Rutgers University, USA), and Louise Kellogg (University of Califorina Davis, USA) will present a Tutorial Talk, a new presentation format at AGU, to encourage discussion about the E5R project. Two postcards ("Greetings from Earth" and "Earth in Five Reactions") were created for the event.
  • Special Issue | American Mineralogist (2019)
    Editors Jie (Jackie) LiSimon Redfern, and Donato Giovannelli have assembled a writing team for a special issue of American Mineralogist. Set for publication in Spring 2019it 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.
  • Wikipedia (2018–19)
    Research from the American Mineralogist special issue is helping the DCO community improve Wikipedia articles about the five reactions.  


Involving the Scientific Community

Workshop attendees

The E5R 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 (University of Michigan, USA) and Simon Redfern (University of Cambridge, UK) polled scientists in person at the Third DCO International Science Meeting in St. Andrews, Scotland in March 2017. The results of this initial poll served as the basis for a larger poll, which was 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 solicited 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 encouraged contributions from the public through social media sites such as Twitter and Reddit.  

The poll was designed to introduce the “five reactions” synthesis initiative while collecting ideas about how to evaluate the importance of a reaction in governing the Earth’s deep carbon cycle. Some critical reactions, for example, have stretched over an extended or 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 are more widespread spatially and occur under broad ranges of pressure and temperature (e.g., redox reactions in solids and liquids). Other important planetary reactions involve dominant carbon-bearing species and other complex reactions that may tie many carbon-bearing species together. Unique reactions that could be used as indicators, tracers, or diagnostic tools for carbon cycling were other possible targets of interest.The importance of the energetics of a reaction also were considered.

The poll consisted of three tiers of questions. Respondents who completed all three tiers were considered for the opportunity to participate in the E5R workshop in Washington, DC, in March 2018. There, Workshop participants used 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 of American Mineralogist, was initiated, in addition to multi-media engagement resources.

Expected Outcomes

AIdea board special issue of American Mineralogist 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 E5R 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.



About the Organizers

  • Jie Li, University of Michigan
    Jie (Jackie) Li University of Michigan, USA
    Jie Li, University of Michigan
    Jie (Jackie) Li
    University of Michigan, USA

    Dr. Jie (Jackie) 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.

  • Simon Redfern, University of Cambridge
    Simon Redfern University of Cambridge, UK
    Simon Redfern, University of Cambridge
    Simon Redfern
    University of Cambridge, UK

    Dr. SImon 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.

  • Donato Giovannelli, Earth-Life Science Institute, Japan
    Donato Giovannelli Earth-Life Science Institute, Japan
    Donato Giovannelli, Earth-Life Science Institute, Japan
    Donato Giovannelli
    Earth-Life Science Institute, Japan

    Dr. Donato Giovannelli is a microbial ecologist working on the microbiology of extreme environments. He currently holds an appointment as a joint EON Research Fellow at the Earth-Life Science Institute, Tokyo and Rutgers University, USA He is also  a Visiting Scholar at the Institute of Advanced Studies in Princeton, USA, and an Adjunct Researcher at the National Research Council of Italy. He received a B.Sc. in Marine Biology (2005) and M.Sc. in Marine Ecology (2007) from the Polytechnic University of Marche, Italy. His current research focuses on two major linked themes: 1) the metabolic and taxonomic diversity of prokaryotes in different geothermally influenced marine ecosystems; and 2) the emergence and evolution of early metabolism. Giovannelli is a member of DCO’s Deep Life community, a leader DCO’s synthesis projects Biology Meets Subduction and Earth in Five Reactions, and was a recipient of DCO’s emerging leader award in 2015.


E5R Group Records Webinar

The Earth in Five Reactions project leaders Li, Redfern, and Giovannelli joined project participant Jennifer Glass in a webinar to share how carbon plays a central role in making Earth habitable. 

Deep Earth Haiku launches

The web app "Deep Earth Haiku" offers would-be poets a chance to write an ode to their favorite deep Earth reaction.

E5R Featured in AGU Tutorial Talk

Earth in Five Reactions is a featured in a Tutorial Talk at AGU's Fall Meeting in Washington, DC.

Lively Workshop Debate

Lively it was! In spite of being threatened by a late spring snow fall in Washington, DC, 50 scientists made their way to Washington DC for the 22-23 March workshop. Beginning at an icebreaker the night before the workshop, participants joined in early and often in the dicussion to determine the five most important carbon-related reactions on Earth.  A full report of their discussion and findings is here.

Giovannelli Joins the Editorial Team

Donato Giovannelli joins the editorial team for Earth in Five Reactions and the special issue of American Mineralogist

Workshop Plans Underway

Details regarding the Earth in Five Workshop were released. Learn more.

Workshop Participants Chosen

And the winners are: 50 scientists were selected to participate in the Earth in Five Workshop in March 2018 based on their survey responses. Those who provided compelling arguments for the  importance of one or more carbo-related reactions received an invitation this week to travel to Washington, DC and defend their position.

Opinions Sought

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 E5R 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

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