Lamont-Doherty Earth Observatory and Department of Earth and Environmental Sciences, Columbia University, Palisades, N. Y.
David Walker was awarded the 2010 Harry H. Hess Medal at the AGU Fall Meeting Honors Ceremony, held on 15 December 2010 in San Francisco, Calif. The medal is for “outstanding achievements in research of the constitution and evolution of Earth and other planets.”
The Harry H. Hess Medal honors “outstanding achievements in research of the constitution and evolution of Earth and other planets.” I can think of no one who is more worthy of this honor than Dave Walker.
Dave’s early work at Harvard as a graduate student and research scientist documents the excitement of the Apollo program lunar sample returns. Even though he was just starting out at that time as a young scientist, Dave quickly became a key figure in the feverish competition between the world’s best experimental labs to piece together the story of the igneous differentiation of the Moon. Much of what we now take for granted about the formation of the lunar crust and mantle came out of the Harvard experimental petrology lab in the 1970s, clearly with Dave Walker’s intellectual stamp on it.
Dave’s interest in the physical mechanisms recorded in lunar igneous rocks led him into the realm of magma physics. An early example of his creative approach to problems in this area are his novel plagioclase flotation experiments, which provided confirmation that the low-density lunar anorthositic crust could have been formed by flotation on the lunar magma ocean. A few years later, as full professor at Columbia’s Lamont-Doherty Earth Observatory, Dave extended this idea to Earth differentiation but with an interesting and equally creative twist. He hypothesized that liquidus olivines would float in silicate melt, not at the Earth’s surface like plagioclase on the Moon but at high pressure through densification of the melt owing to its relatively high compressibility. Dave was also instrumental in elucidating the genesis and evolution of mid-ocean ridge basalts using phase equilibria and pseudoternary phase diagrams. His series of papers on this topic are some of the most cited papers in petrology and geochemistry. Dave is currently a leader in experimental studies of core formation, especially the partitioning of elements between silicates and metals both solid and liquid. His work along with others in the field has elucidated the siderophile element problem for the differentiation of the early Earth, as well as the reactions thought to exist at the core-mantle boundary.
Dave also played a central role in developing equipment to advance high-pressure techniques for the fields of experimental petrology and mineral physics. He made an incredibly clever adaptation of the original multianvil design, simplifying it so that it could be manufactured by any good machine shop at a small fraction of the cost of more complex, high-cost designs. As a result, the high-pressure device known now as the “Walker-type” multianvil has found its way into dozens of experimental petrology and mineral physics labs around the world, which has facilitated research by other experimentalists to understand the constitution and evolution of planetary interiors.
In summary, Dave Walker is a true leader in experimental petrology, both in designing and improving experimental equipment and in pioneering new ideas of the evolution of the Earth, Moon, and planets. His outstanding achievements are most deservingly recognized by the 2010 Harry H. Hess Medal.
—CARL B. AGEE, University of New Mexico, Albuquerque.
I thank my nominators, Carl Agee and Youxue Zhang; my other supporters; and the AGU committees who brought me here. Mike O’Hara, a previous recipient of this medal and one of my heroes, asked these questions in his acceptance speech: Would life have evolved to its present state if each genetic experiment had required prior approval from six referees and a committee? Could Harry Hess have made his great contributions in today’s environment?
It is true, without an annoying review process, that Harry Hess used his World War II ship’s guyot-detecting pinger more than strictly necessary to move troops, but he had considerably less science support than we enjoy today.
Hess’s photo was in the Berkner room at the old Lunar and Planetary Institute adjacent to Johnson Space Center on NASA Road 1 in Houston—a room of memorable small conferences on lunar science and memorable parties. His picture was there because he was a latter-day Moses who, as an Apollo science committee chairman, guided us to, but sadly died on the threshold of, the promised land of lunar sample returns. He was a patriarch in the system of oversight committees and of generous support that built science into national efforts like World War II and Apollo. Mike and I can take our answer from this. Curiosity is a wonderful thing, but it doesn’t hurt to be curious in the context of important, inspirational national goals, which we should contribute to setting and achieving, as Harry Hess did.
I am grateful for the benefits I had from Hess’s Apollo committees. I am grateful for being part of the unique era of planetary exploration, plate tectonics, and mineral physics that illuminated planets. I am grateful to my friends and excellent collaborators, many of whom, like Carl and Youxue, started as my students, postdocs, or mentors. I am grateful to my family, who enabled my scientific activities. And, of course, my sponsors at the U.S. National Science Foundation (NSF), NASA, Department of Energy, Natural Environment Research Council (NERC), Columbia University, and Consortium for Materials Properties Research in Earth Sciences (COMPRES) share prominently in the recognition of this medal. Thank you all very much indeed.
—DAVID WALKER, Lamont-Doherty Earth Observatory and Department of Earth and Environmental Sciences, Columbia University, Palisades, N. Y.