Ariel Anbar, Arizona State University, USA
2019 Samuel Epstein Science Innovation Award medallist
Ariel Anbar is a scientist and educator interested in Earth’s past and future as an inhabited world, and the prospects for life beyond. He is a President’s Professor at Arizona State University on the faculty of the School of Earth & Space Exploration and the School of Molecular Sciences, and a Distinguished Sustainability Scholar in ASU’s Julie Ann Wrigley Global Institute of Sustainability. In science, he and his teams have published over 140 refereed papers on topics ranging from the origins of Earth’s atmosphere to detecting life on other worlds to diagnosing human disease. He directed ASU’s Astrobiology Program from 2009 – 2015. In education, Ariel directs ASU’s Center for Education Through Exploration, which is reinventing digital learning around curiosity, exploration, and discovery.
Ariel arrived at ASU in 2004 after receiving an A.B. in Geological Sciences and Chemistry from Harvard in 1989 and a Ph.D. in Geochemistry at Caltech in 1996, and after spending 8 years on the faculty of the Department of Earth and Environmental Sciences at the University of Rochester. At Harvard, guided by Dick Holland and a suggestion from his father, Michael Anbar, Ariel conducted experiments that demonstrated the potential importance of photochemical oxidation in Archean oceans, especially as a possible source of manganese oxides before the Great Oxidation Event (“GOE”). At Caltech, Ariel worked primarily in Gerry Wasserburg’s “Lunatic Asylum”, working with Rob Creaser and Dimtri Papanastassiou to develop and apply ultra-sensitive negative thermal ionization MS methods to accurately determine the concentrations of rhenium and iridium in seawater. He also worked with Yuk Yung and Mark Allen on several modeling studies of Martian and terrestrial atmospheric chemistry.
After graduate school, first at Rochester and then at ASU, Ariel advanced a team-and-collaboration-based approach to innovation. Helped by Jane Barling and Gwyneth Gordon, Ariel established a research group that pioneered the use of MC-ICP-MS to discover, characterize, and apply natural variations in the stable isotope abundances of transition metals. This research was inspired by the potential of “non-traditional” stable isotope systems as biomarkers and as probes of ancient ocean oxygenation, developed through early interactions with Francis Albarède, Sue Brantley, Tom Bullen, Tim Lyons, Ken Nealson, and Greg Ravizza, as well as by novel ideas about the evolutionary consequences of redox-driven changes in metal availability in ancient oceans developed first with Andy Knoll, and later with graduate student Jennifer Glass and postdoc Felisa Wolfe-Simon.
Ariel’s research group was the first to report natural fractionation of molybdenum isotopes. Led by Barling, and later by Laura Wasylenki in collaboration with Tom Spiro’s group, they discovered how and why molybdenum isotopes fractionate during adsorption to manganese oxides, providing a foundation for the use of this isotopes system to study ancient ocean redox change. A cohort of graduate students and postdocs, including Gail Arnold, Tais Dahl, Yun Duan, and Brian Kendall, as well as many collaborators, worked with Ariel to apply this new isotope system to probe key hypotheses about the timing and tempo of environmental oxygenation, especially in Precambrian carbonaceous shales. With Roger Buick he co-organized a broad team, supported by NASA, to obtain and analyze pristine sediments from just before the GOE, discovering multiple lines of isotopic and other evidence of an early “whiff” of O2 – a discovery which heralded a new wave of research using inorganic proxies to understand the early production of O2 in Earth’s atmosphere and oceans.
Ariel’s group, with Brantley, Spiro, and Stefan Weyer, also conducted key early work on iron isotopes, demonstrating abiotic fractionation in low and high temperature systems, and advancing our theoretical understanding of equilibrium redox fractionation effects.
More recently, Ariel collaborated with Stefan Weyer and then Tom Algeo and Achim Herrmann to develop the uranium isotope system as a paleoredox proxy. Led by graduate students Greg Brennecka and Stephen Romaniello – later joined by Xinming Chen and Feifei Zhang and postdoc Geoff Gilleaudeau – Ariel’s group opened up the carbonate sedimentary record for investigation of changes in ocean oxygenation and their linkages to evolution. Exciting emerging paleoredox projects attempt to calibrate the magnitude and extent of the “whiff” of O2 through pyrite weathering experiments led by graduate student Aleisha Johnson, as well as through the combination of thallium and molybdenum isotope systems in a partnership with Sune Nielsen and Jeremy Owens forged by graduate student Chad Ostrander. New insights into shallow water H2S come from mercury isotopes, led by postdoc Wang Zheng. All of these studies provide fodder for recent and ongoing creative collaborations between Ariel and colleagues in the solid Earth sciences community, funded by NSF, that are providing new insights into how interactions between Earth’s surface and interior shaped the early evolution of the surface redox environment.
Along the way, Ariel encouraged novel applications of the methods of isotope geoscience, particularly to the challenge of understanding and diagnosing human disease. Notably, inspired by the ideas of Joseph Skulan, and led by graduate student Jennifer Morgan, Ariel’s group worked with colleagues at NASA and the Mayo Clinic to develop calcium isotopes as a promising way to monitor and study bone disease. He also pursued environmental applications of iron and mercury isotope systematics with Pierre Herckes, postdoc Brian Majestic, and graduate student Chris Mead.
Ariel is a Fellow of the Geological Society of America, which awarded him the Donath Medal in 2002, and was honored as a Fellow of the Geochemical Society and the European Association of Geochemistry in 2014. Ariel served as President-Elect and President of the Biogeosciences Section of the American Geophysical Union from 2015 – 2019. He was the Endowed Biogeochemistry Lecturer at the Goldschmidt Conference in 2017. He was appointed a Howard Hughes Medical Institute Professor in 2015 in recognition of his work in digital learning innovation, and in 2017 was named one of 10 “teaching innovators” by the Chronicle of Higher Education.