Robin M. Canup

2004 James B. Macelwane Medal Winner

Southwest Research Institute

Robin M. Canup received the Macelwane Medal at the 2004 Fall Meeting Honors Ceremony on 15 December, in San Francisco, California. The medal is given for significant contributions to the geophysical sciences by a young scientist of outstanding ability.


It is a great honor to introduce Robin Canup as a recipient of this distinguished and richly deserved award. Robin studies the formation of planets and their satellites—a subject of intrinsic significance and current fascination. As astrophysicists accumulate evidence of planets around other stars, the question of how to make a solar system like our own has yet to be answered. This tough and complex issue has been tackled by geochemists, but just as importantly by a select number of theoretical astrophysicists who deduce the dynamics of accretion. Robin is a relatively new player in this elite group, but her work has put her at the forefront. There are several important contributions one could highlight.

Her research started with a tidal accretion model that she developed with Larry Esposito, which allowed her to explain some of the rings and moons of Saturn, but also enabled her to demonstrate that an extended protolunar disk would be required to produce our Moon outside the Roche limit. Together with Ida and Stewart, she followed this with N-body simulations of lunar formation and demonstrated that accretion of the Earth’s Moon could have taken as little as a few months.

With Hal Levison and her student Craig Agnor, she performed direct N-body simulations of terrestrial planet accretion. These were the first to utilize modern numerical methods to analyze the large impacts defining the main stages of terrestrial growth, and they confirmed and refined the statistical approach previously utilized by George Wetherill. Following this, Robin, together with Al Cameron and Bill Ward, showed how the mass and angular momentum of impact-ejected material scaled with various impact characteristics. Canup and Asphaug then published their highly regarded 2001 Nature paper demonstrating that a single impact from a Mars-sized object is capable of simultaneously producing an Earth with its final mass, a disk capable of yielding an iron-depleted, lunar-mass Moon, and an Earth-Moon system with its current angular momentum.

Robin has now taken on the formation of the Galilean satellites. Previous models could not reproduce their properties in the light of improved compositional and dynamical constraints. Robin and Bill Ward now have proposed an alternative model in which the satellites form during a protracted period of slow gas inflow into orbit around Jupiter at the end of accretion. This has important implications for the chemistry of these objects.

Linking chemistry with the physics of accretion will be a major feature of this field in the future. Robin and others are already working on this, and the end result should be a proper understanding of how to make a solar system like our own.

Robin Canup is an outstanding scientist who tackles tough issues of deep scientific interest with highly original approaches. She is a wonderful communicator and has an enthusiasm for her science that is inspiring. She has already been recognized by other societies, and in 2002 she was the recipient of the Harold C. Urey Prize of the AAS. It gives me great pleasure to present her to you as a very worthy recipient of this year’s James B. Macelwane Medal..



Thank you Alex, for this very generous citation. It is a great, and to be honest, humbling, honor to be recognized for one’s work by such a large and diverse organization as the AGU. I will do my best to live up to the expectations associated with this award and its distinguished list of previous recipients, and I thank my nominators and the committee for their efforts and support.

I owe a debt of gratitude to many individuals who have helped to shape my personal and professional life. My parents instilled in me a love of science and creative pursuits, and were unlimited in their support of all of my varied interests, from science fairs to ballet classes. Wonderful teachers at Duke—Alex Schramm, John Kolena, and Horst Meyer—inspired and encouraged my interest in physics and astronomy. I remember vividly the afternoon I first interviewed for a graduate research position with my eventual thesis advisor, Larry Esposito. He asked me a list of questions about my relevant experience, and even though I had essentially none, he still hired me, and offered support and wise guidance throughout graduate school.

I am fortunate to have spent the last 6 years as a member of SwRI’s Department of Space Studies in Boulder, Colorado. Our director, Alan Stern, has created an incredible environment for planetary research from which I have benefited greatly, and the talented and energetic people in the group are a joy to interact with. It has been my particularly good fortune to work with Bill Ward, who has been very influential to me as a colleague, mentor, and friend.

I am indebted to NASA and NSF, on whose support I have directly depended for a decade. It is a pleasure and privilege to be able to work in planetary science, a field in which discoveries are ongoing, new ideas and exciting debates abound, and which often captures the imagination and interest of the public as well. Finally, and most important, I thank my best friend (and husband), Rick Mihran, for his inspiring sense of life and 12 wonderful years.

—ROBIN M. CANUP, Southwest Research Institute, Boulder, Colorado