In March 2018, scientists from across DCO’s four research communities met at the Carnegie Institution for Science, USA, for a two-day workshop. Their goal was to decide the five most important chemical reactions that drive the global carbon cycle from atmosphere to core and make Earth a habitable planet. After much discussion, the group voted for the winners: hydrogenation/dehydrogenation, carboxylation/decarboxylation, carbonation/decarbonation, aqueous silicate melt/solid, and hydration/dehydration.
These reactions are now the focus of a special collection of papers in American Mineralogist called "Earth in Five Reactions: A Deep Carbon Perspective." Extreme Physics and Chemistry (EPC) Community member Jie Li (University of Michigan, USA), EPC and Reservoirs and Fluxes Community member Simon Redfern (University of Cambridge, UK), and Deep Life Community member Donato Giovannelli (University of Naples "Federico II," Italy) edited the collection. Articles have appeared online as they been accepted, with the complete issue of 12 papers expected in February 2020. The special issue includes a preface by the editors and a perspective paper by DCO Executive Director Robert Hazen (Carnegie Institution for Science, USA).
“The idea of this synthesis is to bring people’s attention to chemical reactions,” said Li. “It’s a very good way for people to understand the evolution of Earth and other planets, and I think that this unique perspective will have a profound impact on how we think about habitability as a whole.”
Ultimately the papers in the collection will include six invited review articles and several contributed research papers. Emily Stewart (Yale University, USA) and colleagues have published the review article on “Carbonation and decarbonation reactions: Implications for planetary habitability.” The reviews by Marie Edmonds (University of Cambridge, UK) et al., on carbon outgassing from melted rock and the uptake of carbon dioxide by alkaline water, and one by Catherine McCammon (Bayerisches Geoinstitut, Germany) et al. on deep Earth carbon reactions through time and space are in press. In submitted reviews, Cody Sheik (University of Minnesota, Duluth, USA) et al. focuses on carboxylation and decarboxylation, Shawn McGlynn (Tokyo Institute of Technology, Japan) et al. cover hydrogenation and dehydrogenation, and Alberto Vitale Brovarone (University of Turin, Italy), et al. report on hydration and dehydration reactions.
The Earth in Five Reactions special collection not only synthesizes what DCO scientists have already learned about how the deep carbon cycle contributes to a livable planet but also highlights new directions for future research. “I think we have identified a lot of unknowns, especially the kinetics of the reactions – how quickly the reactions would occur under a diverse range of geological environments,” said Li. “Earth science is about the history of our planet and time is a really critical component.”
Scientists also don’t know how some of these reactions occur at the temperatures and pressures of deep Earth. Three reactions that were nominated but didn’t make the final cut were reactions that are predicted to take place hundreds to thousands of kilometers deep inside Earth, such as the ones that form diamonds (McCammon et al, in press). Investigations into these reactions likely will factor into the next decade of carbon research.
Table of contents
Click on the titles below to access the papers.