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Obituary Paul W. Gast 1930–1973
Oeochimica
et CosmochimicaActa, 1076, Vol. 39, pp. 93 to 94. Pergamon Press. Printed in Northern Ireland
Obituary PAUL
w.
GAST*
1930-1973 ALTHOUGH Paul Gast had been seriously ill long before his death in May, 1973, the fact that he remained a powerful and creative force in our science until the very end made it difficult for a while to think of him in other than the present tense. Now his life and work are becoming part of our common past. This is written as an appreciation of what he did for us. I first met Paul Gast in the fall of 1953 when we both came to the Department of Terrestrial Magnetism of the Carnegie Institution of Washington. When I inquired concerning his planned research, he told me that he was going to devote his life to unde~tanding the nature of the Earth’s mantle. Most graduate students dont aay things like that. However, when Paul said this it seemed a perfectly reasonable and even modest thing to say. He set right to work doing so, probably unaware that he had set his goals too narrowly and that he would have to face the challenge of understanding the Moon’s mantle as well, At that time the mantle was a somewhat mythological place from which basalts were derived. Unfortunately, the composition of the basalts fell far short of defining the com~sition of the mantle. One of Gast’s earliest and major contributions was the recognition that the strontium isotopic composition of recent basalts was a faithful relic of the rubidium-strontium ratio of their mantle source, regardless of what chemical complexities were involved in the generation of basalts from mantle ratio was remarkably material. The value found for this ~bi~um~ontium low-an order of magnitude lower than if the source had the chondritic Rb-Sr ratio. This discovery opened the p”ay to a continuing discussion of the ways in n-hich the chemical compositions of the terrestrial planets and the parent bodies of the meteorites were different and the ways in which they were similar. These tu-o rather rare elements may have seemed a precarious starting point for such far-reaching generalizations. It is quite remarkable that the somewhat accidental linkage of these elements by their nuclear properties should have proven so geochemically useful. The geochemical sig~fican~ of ~bi~urn-s~ontium fractionation led Gast and others to a more general discussion of the role of volatility in determining the potassium-caloium and potassium-uranium ratio of planetary bodies. The abundance of the latter two elements is fundamental to the thermal and magmatic history of a planet. Other elements of course played important roles. Among these were lead and its isotopes, and the rare-earth elements, the geochemical importance of which was brought out by the neutron activation m~s~ernen~ of Haskin and others. Gast applied his geochemical insight to the question of what these and other elements could tell us regarding the chemical processes linking the Earth’s crust and mantle. One of the major fruits of this work was Gast’s 1968 paper in this journal: “Trace
* First V. M. Goldschmidt medallist (1972) of the Geoclhemicrtl Society. 93
94
PAUL TV. GAST
element fractionation and the origin of tholeiitic and alkaline magma types”. From this work followed a deeper appreciation of the primary importance of partial melting in petrogenesis and planetary difterentiation. All of this work was doubly timely. It fitted in a natural way into the plate tectonic revolution of the 1960’s, and it set the stage for understanding the chemical history of the Noon, which became possible with the advent of lunar exploration shortly thereafter. During these years Paul Gast performed well the other duties of a professional and scholarly career. He was an associate editor of three journals, and an impo~ant member of university and federal committees and a counselor of the Geochemical Society. This professional and public service barely foreshadowed the great contribution Gast was to make during the next few years. The Apollo program of lunar exploration represented an enormously complex mixture of human adventure, inspired achievements in engineering, and somewhat less inspired public relations, all in the context of a contest between the USA. and the U.S.S.R. for demonstrated technological superiority. There was no built-in guarantee that science was an essential element in this complex. The fact that the lunar program turned out to be a great scientific program as well was due in large part to the work of a small group of people, primarily associated with the Lunar Sample Analysis P~~n~g Team of the M~ed Spacecraft Center. Paul Gast was one of these. Officially reporting at a fairly low level in the federal hierarchy, they proved capable of interacting successfully at the day to day operationa level in Houston as well as being heard when necessary in Washington. Gast went even further than the others in leaving his academic position at Columbia University to become Chief of the Planetary and Earth Science Division of M.S.C. Blany of his colleagues could not understand why he did this, and feared he would be swallowed in the federal bureaucracy. It would be valuable to understand fully how he avoided this. The fact is that he built a strong scientific enclave at M.S.C. which was able to not only carry out valuable scientific investigations but to achieve a necessary and continuing place for science in the management of the Apollo program. Most men with similar formal q~al~cations would have failed at this task. Through some comb~ation of intelligence, experience, immunity to the pitfalls of power, self-confidence, honesty, and faith that the system could be made to work, he succeeded. The time he was granted to do this was too short, but he made it all count. Mastery of our current problems in most areas of national concern will require more of his kind. G. W. W.
et CosmochimicaActa, 1076, Vol. 39, pp. 93 to 94. Pergamon Press. Printed in Northern Ireland
Obituary PAUL
w.
GAST*
1930-1973 ALTHOUGH Paul Gast had been seriously ill long before his death in May, 1973, the fact that he remained a powerful and creative force in our science until the very end made it difficult for a while to think of him in other than the present tense. Now his life and work are becoming part of our common past. This is written as an appreciation of what he did for us. I first met Paul Gast in the fall of 1953 when we both came to the Department of Terrestrial Magnetism of the Carnegie Institution of Washington. When I inquired concerning his planned research, he told me that he was going to devote his life to unde~tanding the nature of the Earth’s mantle. Most graduate students dont aay things like that. However, when Paul said this it seemed a perfectly reasonable and even modest thing to say. He set right to work doing so, probably unaware that he had set his goals too narrowly and that he would have to face the challenge of understanding the Moon’s mantle as well, At that time the mantle was a somewhat mythological place from which basalts were derived. Unfortunately, the composition of the basalts fell far short of defining the com~sition of the mantle. One of Gast’s earliest and major contributions was the recognition that the strontium isotopic composition of recent basalts was a faithful relic of the rubidium-strontium ratio of their mantle source, regardless of what chemical complexities were involved in the generation of basalts from mantle ratio was remarkably material. The value found for this ~bi~um~ontium low-an order of magnitude lower than if the source had the chondritic Rb-Sr ratio. This discovery opened the p”ay to a continuing discussion of the ways in n-hich the chemical compositions of the terrestrial planets and the parent bodies of the meteorites were different and the ways in which they were similar. These tu-o rather rare elements may have seemed a precarious starting point for such far-reaching generalizations. It is quite remarkable that the somewhat accidental linkage of these elements by their nuclear properties should have proven so geochemically useful. The geochemical sig~fican~ of ~bi~urn-s~ontium fractionation led Gast and others to a more general discussion of the role of volatility in determining the potassium-caloium and potassium-uranium ratio of planetary bodies. The abundance of the latter two elements is fundamental to the thermal and magmatic history of a planet. Other elements of course played important roles. Among these were lead and its isotopes, and the rare-earth elements, the geochemical importance of which was brought out by the neutron activation m~s~ernen~ of Haskin and others. Gast applied his geochemical insight to the question of what these and other elements could tell us regarding the chemical processes linking the Earth’s crust and mantle. One of the major fruits of this work was Gast’s 1968 paper in this journal: “Trace
* First V. M. Goldschmidt medallist (1972) of the Geoclhemicrtl Society. 93
94
PAUL TV. GAST
element fractionation and the origin of tholeiitic and alkaline magma types”. From this work followed a deeper appreciation of the primary importance of partial melting in petrogenesis and planetary difterentiation. All of this work was doubly timely. It fitted in a natural way into the plate tectonic revolution of the 1960’s, and it set the stage for understanding the chemical history of the Noon, which became possible with the advent of lunar exploration shortly thereafter. During these years Paul Gast performed well the other duties of a professional and scholarly career. He was an associate editor of three journals, and an impo~ant member of university and federal committees and a counselor of the Geochemical Society. This professional and public service barely foreshadowed the great contribution Gast was to make during the next few years. The Apollo program of lunar exploration represented an enormously complex mixture of human adventure, inspired achievements in engineering, and somewhat less inspired public relations, all in the context of a contest between the USA. and the U.S.S.R. for demonstrated technological superiority. There was no built-in guarantee that science was an essential element in this complex. The fact that the lunar program turned out to be a great scientific program as well was due in large part to the work of a small group of people, primarily associated with the Lunar Sample Analysis P~~n~g Team of the M~ed Spacecraft Center. Paul Gast was one of these. Officially reporting at a fairly low level in the federal hierarchy, they proved capable of interacting successfully at the day to day operationa level in Houston as well as being heard when necessary in Washington. Gast went even further than the others in leaving his academic position at Columbia University to become Chief of the Planetary and Earth Science Division of M.S.C. Blany of his colleagues could not understand why he did this, and feared he would be swallowed in the federal bureaucracy. It would be valuable to understand fully how he avoided this. The fact is that he built a strong scientific enclave at M.S.C. which was able to not only carry out valuable scientific investigations but to achieve a necessary and continuing place for science in the management of the Apollo program. Most men with similar formal q~al~cations would have failed at this task. Through some comb~ation of intelligence, experience, immunity to the pitfalls of power, self-confidence, honesty, and faith that the system could be made to work, he succeeded. The time he was granted to do this was too short, but he made it all count. Mastery of our current problems in most areas of national concern will require more of his kind. G. W. W.