Francis Nimmo

2007 James B. Macelwane Medal Winner

University of California

Francis Nimmo was awarded the 2007 James B. Macelwane Medal at the AGU Fall Meeting Honors Ceremony, which was held on 12 December 2007 in San Francisco, Calif. The medal is “for significant contributions to the geophysical sciences by a young scientist of outstanding ability.”


Francis is an outstanding planetary scientist. He has contributed to the interpretation and modeling of a remarkably wide range of solid bodies, both rocky and icy. His work is characterized by a deep appreciation of the physical processes that control the evolution and appearance of planetary bodies, and a highly developed ability to respond quickly to the remarkable recent flow of spacecraft data about our solar system, perform relevant calculations, and make balanced judgments of competing hypotheses. The strength of his effort and merit for the James B. Macelwane Medal lies in the cumulative impact of his work. The pace and diversity of significant contributions for the past 3 or so years are particularly outstanding. At the risk of naming every solid body in the solar system above a certain size, important contributions have been made to our understanding of Mercury, Venus, Earth, Mars, Europa, Ganymede, Enceladus, and Triton. He has even gotten involved in the interpretation of isotope systematics and their application to our understanding of planetary accretion. I expect I have left something out.

Francis is English; he began his research career with a Ph.D. at University of Cambridge, working with Dan McKenzie on the tectonics of Venus. He subsequently spent some time at California Institute of Technology, at University College London, and at University of California, Los Angeles; he is now well established at UC Santa Cruz. In this career path, he has moved steadily away from collaborations that were mainly with much more senior scientists to diverse collaborations with a large number of scientists, many of whom are more junior, including students. Very briefly, these efforts have included an innovative analysis of the deformation of viscoelastic shells on icy bodies with application to the different kinds of features seen on the surface of Europa and Ganymede; an assessment of the possible role of 40K in the thermal history of Earth’s core, motivated by a possible shortfall in energy sources needed to sustain the geodynamo over geologic time; quantitative models of crustal evolution on Mars and Mercury; and a well-argued case for true polar wander on Enceladus. This work on Enceladus shows many of the abilities that Francis has: the bringing together of several physical ideas (models of ice upwellings, deformation of the brittle layer, resulting true polar wander), a concise and technically outstanding quantitative analysis, and an effective collaboration.

One would not normally expect to see a single scientist develop so many collaborative efforts in such a short time. These collaborations make sense and are a wonderful way to have a large impact in planetary science. His breadth is also expressed in review papers, where Francis shows a well-developed appreciation of the contributions in so many areas.

There are usually more people deserving of the Macelwane Medal than the number awarded. An additional consideration is the impact that the awardee is likely to have in the future. In this respect, Francis is particularly outstanding in the promise that he holds, and I look forward to his future efforts.

—DAVE STEVENSON, California Institute of Technology, Pasadenaz


Thank you, Dave, and thanks also to AGU and the committee for this unexpected honor, and to my nominators for their support. The list of previous winners, and what they went on to achieve, is frankly intimidating; in my view, this award really recognizes the extraordinary scientific advances made by spacecraft missions in the past decade. Observational constraints in planetary science are usually sparse and disparate, so that unselfish collaboration in research is not so much a choice as a necessity. Even so, my collaborators have been exceptionally generous with their time, data, and talents. Essentially none of my work would have been possible without their help, so I regret having to thank them collectively, rather than individually; they know who they are, though. I have also been exceptionally lucky with my graduate and postdoctoral advisors, Dan McKenzie and Dave Stevenson. They were both always available to dispense sage advice, scientific and otherwise, and were willing to share their opinions on absolutely anything. Now that I am advising students, I appreciate their mentoring skills much more than I did at the time. A final, but very important, person to thank is Professor Emily Brodsky, my wife. She was willing to move institutions, and disrupt her own research program, in order to give mine a chance to get started. I am, and continue to be, extremely grateful, and cannot imagine a better person to share my life with. The organization most central to my work is NASA, 50 years old in 2008 and an outstanding example of AGU’s principles. Not only are NASA data made freely available worldwide, but also NASA allows foreign scientists to take part in spacecraft missions. The only reason I am doing planetary science today is because Dan was a team member on the Magellan mission. One lecture on Venus was enough to convince me that planetary science was much more exciting than any terrestrial topic (even dinosaurs). Two other organizations that greatly helped my early career were Magdalene College, Cambridge and the Royal Society. Both provided research support with almost no strings attached, and were willing to let me spend significant amounts of time in the United States. More recently, my colleagues at University of California, Santa Cruz have been both very welcoming and a source of great intellectual support. Because planetary science is often data-limited, one has great freedom in developing theories, while the time-scales of spacecraft missions mean that it is often the next generation that will prove you wrong! More seriously, the expansion of our knowledge of this, and now other, planetary systems in the past half century has been truly breathtaking, and I hope it will continue in the next. Thank you once again.

—FRANCIS NIMMO, University of California, Santa Cruz