Sean C. Solomon

2005 Harry H. Hess Medal Winner

Carnegie Institution of Washington, Washington, D.C.

Sean C. Solomon received the Harry H. Hess Medal at the 2005 Fall Meeting Honors Ceremony, which was held on 7 December in San Francisco, Calif. The medal is given for outstanding achievements in research on the constitution and evolution of the Earth and other planets.


“It is a privilege to present Sean C. Solomon as the American Geophysical Union’s Harry H. Hess Medal recipient. During more than 30 years of accomplished research he has established himself as one of the remarkable leaders in geophysical research today.

“Sean began his career working on the nature of seismic attenuation and the implications for upper mantle structure. This early work was the beginning of a long-term interest in understanding the thermal structures of planetary interiors.

“In 1978, he published a noteworthy paper in Geophysical Research Letters that provided an elegant explanation of the thermal evolution of small one-plate planets like the Moon and Mercury in the absence of plate recycling. This ‘one-plate planet’ concept has become the paradigm for understanding the tectonics of the terrestrial planets. Sean has played the leadership role over more than two decades in the understanding of the contrasting evolutionary paths of Venus and Earth and is responsible for some of the most important results from the Magellan mission.

“Sean’s interest in the Earth’s mid-ocean ridge system has been long-standing and diverse. His most important contributions, following his earliest work on shear wave attenuation and melting beneath the Mid-Atlantic Ridge, have been in the understanding of the seismicity of oceanic ridges and transforms, and the use of active and passive marine seismic experiments to probe crustal and upper mantle structures and processes. During this era Sean was actively involved in seagoing fieldwork and at MIT [Massachusetts Institute of Technology, Cambridge] led one of the earliest ocean-bottom seismometer groups.

“Recently, Sean has developed an interest in testing the plume hypothesis for the origin of hot spots, and with his colleagues in the Department of Terrestrial Magnetism (DTM) at the Carnegie Institution [Washington, D.C.], he is playing the lead role in an impressive set of experiments.

“Sean maintains a major leadership role in studies of the terrestrial planets. He has long been interested in the role of cooling strain in the evolution of one-plate planets, and to make a major step forward in these efforts he created, and has become the principal investigator of NASA’s mission to Mercury (called MESSENGER, the Mercury Surface Space Environment, Geochemistry, and Ranging mission) that was successfully launched in 2004.

“Throughout his career Sean has been a selfless mentor to his younger colleagues and students, many of whom are today leaders in their own right. He has contributed substantially to the community through the leadership of agency initiatives at NASA and the U.S. National Science Foundation, through his leadership of the AGU, and through his superb job as director of DTM.

“Sean’s contributions to our science are remarkable in their depth and diversity. His research papers are notable for their rigor—they stand the test of time in fast moving fields that cause many lesser publications to be superseded. He combines a keen understanding of the importance of high-quality observations with an ability to develop elegant theoretical insights that build compelling and powerful models. Sean is unique in the breadth of his abilities and the magnitude of his research accomplishments, and thus it is wise and appropriate that he receive the Harry H. Hess Medal from the American Geophysical Union.”

—G. MICHAEL PURDY, Lamont-Doherty Earth Observatory, Palisades, N.Y.


“The Harry H. Hess Medal has special meaning to me on several levels, including tonight’s citationist, the professional society sponsoring the award, and the individual for whom the medal is named.

“Mike Purdy and I have partnered in five oceanographic cruises, cosupervised six Ph.D. students, and coauthored 15 papers. As anyone who has been to sea with Mike knows well, at every dinner he dresses more or less as you see him now, a sartorial model for us all. Thank you, Mike.

“AGU is my principal scientific society. I have given 40% of my professional talks at AGU meetings, published 50% of my papers in AGU journals, and devoted time to AGU governance. I even chaired the committee that persuaded John Orcutt to stand for AGU president. A coincidence tonight, I am sure.

“The first AGU meeting I attended was in spring 1967. The plate tectonic revolution was at its eruptive peak, and in two remarkable sessions the giants of the field rose one by one to lay out the latest observations in support of seafloor spreading, subduction, and plate kinematics. As a first-year graduate student I was enthralled, and I returned home quite sure that what I had witnessed would be typical of every AGU meeting I would attend thereafter.

“One of those who spoke then was Harry Hess, a scientific hero of mine. A man of remarkable breadth, Hess made fundamental contributions to mineralogy, petrology, the understanding of layered igneous complexes, marine geology and geophysics, and deep crustal drilling. Moreover, his creativity did not ebb with age; his deduction of the nature and cause of the anisotropy of the oceanic upper mantle and his paper “History of ocean basins”—the revolutionary shot heard round the geoscience world—were written late in his life and stand as inspirations to all of us with graying hair and expanding foreheads.

“Hess, too, felt a responsibility to return what science had given him through professional service and to write about the science issues of his day. He was president of two sections of AGU. He chaired the Space Science Board during the years in which plans were laid for the geological exploration of the Moon and the opening search for evidence of life on Mars. Sadly, Hess died in 1969 while chairing a meeting of that board, weeks before he was due to be sent some of the first lunar samples returned to Earth by the Apollo 11 astronauts.

“I am extraordinarily fortunate: I’ve worked at two institutions—MIT and the Carnegie Institution of Washington—that have allowed me to set my own research directions; I’ve collaborated with dozens of outstanding students, postdoctoral scientists, and colleagues; I’ve been blessed with a supportive wife and family; and I’ve been alive when the exploration of the solar system and much of the detailed investigation of the Earth’s interior were first carried out.

To my nominators, the medal committee, and the Union I am deeply appreciative of their recognition of that good fortune.”

—SEAN C. SOLOMON, Carnegie Institution of Washington, Washington, D.C.