Nicolas Dauphas was awarded the 2011 James B. Macelwane Medal at the AGU Fall Meeting Honors Ceremony, held on 7 December 2011 in San Francisco, Calif. The medal is for “significant contributions to the geophysical sciences by an outstanding young scientist.”  

I am honored to introduce Nicolas Dauphas, the outstanding isotope geochemist and cosmochemist of his generation, as a recipient of AGU’s 2011 James B. Macelwane Medal. Nicolas came to Chicago as a postdoc in 2002 after getting his Ph.D. at Centre de Recherches Pétrographiques et Géochimiques (CRPG), in Nancy, France, with Bernard Marty and Laurie Reisberg and 2 years later joined the faculty of the University of Chicago in the Department of the Geophysical Sciences and the Enrico Fermi Institute.

Nicolas Dauphas’s contributions to geochemistry and cosmochemistry are remarkable for their breadth and depth, covering geochemical processes at all scales and times, from age of the galaxy to evolution of ancient and modern igneous rocks. Recently, he and collaborators at the California Institute of Technology (Caltech) discovered that the long-­sought but elusive carriers of 54Cr anomalies in meteorites are chromium-­rich nanoparticles with huge 54Cr excesses. The discovery of this new type of presolar grain solved a 20-­year-­old problem. He used the iron and nickel isotopic compositions of meteorites to show that stellar debris containing 60Fe was injected into the solar system early and was well mixed, disproving an earlier assertion of late addition of 60Fe to the solar system. He used the Th/U ratio of meteorites to measure the age of the galaxy and, with Ali Pourmand, recently used Th/Hf ratios and W isotopic compositions to conclude that Mars formed very rapidly, in only 4 million years. He used the correlation of nucleosynthetic isotope anomalies in molybdenum and ruthenium isotopes to conclude that the chemical composition of the feeding zone of planetesimals that came together to form the Earth did not change drastically with time. He developed an elegant model for the origin of the Earth’s atmosphere using two sources, blow-­off of initial gases and infall of comets, to explain the elemental and isotopic abundances of all of the noble gases, thereby solving the “missing xenon” paradox. He showed how iron isotopic compositions of mantle rocks might be used to constrain the redox conditions of mantle melting from the Archean to the present. Another recent breakthrough with Fang-­Zhen Teng involves documenting diffusive isotopic fractionation of magnesium and iron in olivine in komatiites and the Kilauea Iki lava lake and using isotopic zoning profiles to infer cooling histories. This novel technique has great potential for constraining the histories of many other igneous olivine-­bearing rocks.

Nicolas Dauphas has built a superb research group and attracted excellent students and postdocs, several of whom have already gone on to faculty positions. His honors include the Nier Prize of the Meteoritical Society, the Houtermans Medal of the European Association of Geochemistry, a Packard Fellowship, a Moore Distinguished Visiting Scholarship at Caltech, and now the Macelwane Medal. Nicolas Dauphas has a very special combination of curiosity, intuition, imagination, and impressive modeling and experimental skills, and I have no doubt that the best is yet to come.


—Andrew M. Davis, Department of the Geophysical Sciences and Enrico Fermi Institute, University of Chicago, Chicago, Ill.

Thank you, Andy, for your kind words. I first want to extend my gratitude to the individuals who supported me and to AGU for endorsing that nomination. It is a great and humbling honor to receive the James B. Macelwane Medal from AGU. Looking at the list of past recipients, one cannot help being impressed by the great things that they went on to achieve. I take this award not only as recognition of past achievements but also as inspiration to continue exploring. I have always had a passion for rocks and geology, which led me to study at the Ecole Nationale Supérieure de Géologie, in Nancy, France. I was being trained as a petroleum geologist when I had the opportunity to attend Bernard Marty’s class on geochemistry; it covered everything from stellar nucleosynthesis to chemical weathering. What kind of scientific field can claim such diverse topics? Bernard did a fantastic job connecting everything, and the following year I started a Ph.D. thesis under his and Laurie Reisberg’s guidance. I discovered that large planetary objects carried isotopic anomalies for molybdenum, which is a refractory element. This took everyone by surprise and was met with some skepticism. Ten years later, though, discoveries of isotopic anomalies for other refractory elements do not raise an eyebrow. Working with Bernard, I also learned about volatile elements, which led me to propose a model involving comets to explain the origin of Earth’s atmosphere. With the models of Pepin and Tolstikhin, it is one of the three quantitative explanations of Earth’s atmosphere. To this day I think that some of the outstanding questions in Earth science lie in the atmospheric composition, and I have strong hopes that measurement of a comet by the Rosetta mission will help resolve these questions. Since 2002 I have been working at the University of Chicago, first as a postdoc and then as faculty. There I have been surrounded by outstanding scientists who have nourished my thinking: Frank Richter, Andy Davis, Bob Clayton, Larry Grossman, Fred Anderson, Fred Ciesla, Mike Pellin, Ray Pierrehumbert, and David Rowley to name just a few. Geochemists at the University of Chicago have developed a style that is grounded in chemistry and physics, which suits me well. In my group, the Origins Lab, we have developed new analytical techniques and modeling tools that have allowed us to study the origin of the oldest sediments on Earth, to identify microbial iron respiration in sediments, to determine the galaxy’s age, to establish Mars as a stranded embryo, and to constrain the abundance of 60Fe in the early solar system, among numerous other investigations. Students and postdocs have contributed tremendously to these adventures, and I wish to thank them for joining the ship: Vincent Busigny, Ali Pourmand, Fang-­Zhen Teng, Paul Craddock, Thomas Ireland, Liping Qin, Haolan Tang, Junjun Zhang, Corliss Sio, and François Tissot. Once again, let me thank the individuals who nominated me and AGU for the tremendous honor of receiving the Macelwane Medal. —Nicolas Dauphas, Department of the Geophysical Sciences and Enrico Fermi Institute, University of Chicago, Chicago, Ill.

Nicolas Dauphas was awarded the 2011 James B. Macelwane Medal and a Conferred Fellow at the AGU Fall Meeting Honors Ceremony, held on 7 December 2011 in San Francisco, Calif. The medal is for “significant contributions to the geophysical sciences by an outstanding young scientist.”