Russell J. Hemley and Ho-kwang Mao

2005 Balzan Prize
deed, one of the primary aims of modern mineral physics has been to supply the
missing link between the global and the atomic – how planetary structure, dynamics,
and evolution are controlled by the fundamental physical and chemical
properties of the component materials, and not just for the Earth but also for all
bodies in the solar system and beyond. The field of mineral physics not only supplies
that link, it has also established entirely new avenues of research. An array
of transformations in solids, liquids, and gases under the extreme pressure-temperature
conditions of deep planetary interiors have been discovered, thus identifying
the “brave, new world” of materials within planets, which is utterly different
from that observed at or near planetary surfaces. Detailed in situ measurements
of the physical and chemical properties of a broad range of relevant materials
have been carried out up to the pressures found at the center of the Earth
(3.6 Mbar). These measurements have revealed new bonding, electronic, magnetic
and structural states in materials, requiring the extension of established precepts
developed in the early years of quantum mechanics by Linus Pauling 7 and
Eugene Wigner and Frederick Seitz. 8 Due to pressure-induced changes in chemical
affinities, the reactivities of otherwise familiar elements and compounds are
totally altered, and entirely new classes of materials appear. For organic materials,
these changes occur at very modest pressures, with results that have major implications
for life in extreme environments elsewhere in the solar system. At combined
high pressures and temperatures, novel electronic and structural properties
emerge, creating new phases that can be recovered to ambient conditions. Indeed,
understanding the broad spectrum of phenomena exhibited in simple molecular
systems up to multimegabar pressures and from the millikelvin range to
the highest temperatures goes to the core of our understanding of materials. 9
Professional Background
In 1964, Mao started his Ph.D. thesis work at the University of Rochester, using
the diamond-anvil cell for studies of mantle minerals under the guidance of
William A. Bassett and Taro Takahashi. In 1968, he joined the Geophysical Laboratory,
a world-leading high-pressure center, for post-doctoral work on crystalfield
spectroscopy of lunar and terrestrial minerals with Peter M. Bell, himself a
student of Francis Birch and Percy W. Bridgman, recipient of the 1946 Nobel
Prize in Physics for his contribution to high-pressure research. At Carnegie, Mao
broadened his expertise and began to utilize other high-pressure devices such as
the hydrothermal bomb, Birch gas apparatus, Bridgman squeezer, piston-cylin-
10