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Stuart Ross Taylor (1925–2021): A tribute to his life and scientific career

2021; Wiley; Volume: 56; Issue: 9 Linguagem: Inglês

10.1111/maps.13733

1945-5100

S. M. McLennan, Roberta L. Rudnick,

Geological and Geophysical Studies

Stuart Ross Taylor, always known by his middle name Ross, was born in Ashburton, New Zealand, on November 26, 1925, and died peacefully in Canberra, Australia, on May 23, 2021, at the age of 95, surrounded by his wonderful and loving family. He was one of the finest and most influential geochemists and planetary scientists of his generation. He was a gracious and humble person and had a rich and fulfilling life. Ross is survived by his wife of 63 years, Noël Taylor (née White); his children Susanna, Judith and her partner Michael, and Helen; his grandson Angelo; and his brother Forbes. Ross had many interests. He was exceptionally well read in history, especially military history, and extremely knowledgeable about the battles and politics of the First World War (which impacted his family greatly). Anyone reading footnotes to his many books appreciates his always witty and often wry historical perspectives and anecdotes. Ross also loved baroque and classical music and was especially fond of the works of Mozart. A New Yorker magazine was usually within close reach. There were only a few things that he did not much like. He had a deep skepticism of committees, often quoting the adage that "no committee ever wrote a symphony." He had an aversion to scientific jargon, for example, calling the terms allochthonous and autochthonous those "terrible twins." Aware of Churchill's assurance that "history will be kind to me, for I intend to write it," Ross left us with more thorough and personal recollections of his life and career than we could ever accomplish in this brief memorial, by way of autobiographical sketches and published interviews (Crompton, 2000; Marvin, 2002; Taylor, 1994, 2016). Ross had a truly remarkable scientific career, working on some of the most important problems in the earth and planetary sciences, that spanned 65 yr. His primary analytical approach was trace element geochemistry, Goldschmidt's own specialty, but his knowledge of geochemistry and cosmochemistry was encyclopedic. His first paper was published in 1955 (Mason & Taylor, 1955) and his last appeared in 2019 (Taylor, 2019). In between he published more than 240 papers and 10 books (see Selected Publications below). His writing style can be described as accessible and economical and always highly engaging. His scientific philosophy and approach were influenced by Karl Popper, with whom he overlapped at Canterbury University College, and Bertrand Russell, whom he read extensively and quoted often. His career began at Canterbury University College, University of New Zealand, in Christchurch where he obtained his B.Sc. (1948), double majoring in geology and chemistry, and M.Sc. with Honours (1951) in geology (working on stratigraphy) for which he received the Sir Julius von Haast Prize, his first of many awards. He was mentored by his geology and mineralogy professors Robin Allan and Brian Mason. After a brief stint in industry as a lab technician, he was invited to undertake Ph.D. research in the "new field" of geochemistry at Indiana University with Brian Mason, who moved there in 1947. Brian was Goldschmidt's last student in Oslo (but finished his own Ph.D. in Stockholm due to the invasion of Norway) and Ross was always proud of the direct academic lineage to Goldschmidt (as are Ross's students and their students). His first task as a Ph.D. student was to proofread the first edition galleys of Mason's classic book Principles of Geochemistry (Mason, 1952). Ross's Ph.D. dealt with the geochemistry of volcanic and metamorphic rocks from New Zealand (Taylor, 1954). The Indiana Geological Survey had a state-of-the-art emission spectroscopy laboratory and there Ross first learned how to make quantitative trace element measurements with Dick Leininger. He later received degrees from Oxford: M.A. in 1956 (permitting him to lecture there) and D.Sc. in 1978. With Henrich Neuman's encouragement, Ross applied for and obtained a position at the University of Oxford, initially as Demonstrator but was quickly promoted to Lecturer. There he worked closely with Louis Ahrens, then the world's pre-eminent geochemist (Taylor, 1995), and set up an emission spectroscopy laboratory focusing on improving the accuracy and precision of the method. This led to Ross being invited to help Ahrens write the second edition of Spectrochemical Analysis, Ross's first book, an experience having profound ramifications for his career a decade later. His research initially focused on alkali elements and feldspar chemistry (with Knut Heier). He met and was greatly influenced by Harold Urey who spent a sabbatical at Oxford in 1956, leading to Ross's extensive involvement in tektite research and planetary science. At Oxford, Ross also met the love of his life, Noël White from Perth, Australia, who was on a CSIRO Overseas Studentship working on organic X-ray crystallography with Dorothy Hodgkin, a future Nobel laureate. They were married in Christ Church Cathedral in 1958. In 1958, Ahrens departed Oxford to become the Chair of Chemistry at the University of Cape Town and Ross followed soon after to set up a geochemistry group in the Geology Department, as a Senior Lecturer. At Cape Town, his research on tektites really took off. His first Ph.D. students date from this time: Tony Erlank and Peter Kolbe (who finished at the Australian National University [ANU]). Although Ross's time at the University of Cape Town was productive, by 1960 Noël and he became very uncomfortable with the political situation in South Africa. Accordingly, in 1961, John Jaeger recruited Ross to the Department of Geophysics in the Research School of Physics (later the Department of Geophysics and Geochemistry, finally becoming the Research School of Earth Sciences [RSES] in 1974) at ANU. At RSES, Ross set up an emission spectroscopy laboratory (producing publishable data until 1980 when his innovative ICP-OES facilities became fully operational) but also pioneered spark source mass spectrometry as a more sensitive and precise method for analyzing a wider range of trace elements. The trace element group was small by RSES standards, which suited Ross's approach to science very well. At any given time, he usually had one graduate student, one Research Fellow, and one or two technical staff working with him. However, the vitality of the group was ensured by a constant stream of visitors from all over the world—first-year graduate students to highly seasoned scientists—who came to work with Ross and collect reliable data. Everyone followed the same rules: Stay in the lab for at least 3 months and collect your own data. For nearly 30 yr, Ross's research endeavors at RSES flourished. Ross retired in 1990 (which was then mandatory at age 65) and departed RSES; in spite of his research program being vibrant, Ross's political situation at RSES had always been challenging. Nevertheless, he remained at ANU, taking up Visiting Fellowships in the Department of Nuclear Physics in the Research School of Physics and from 2000 in the Department of Earth and Marine Sciences (EMS) where he re-discovered classroom teaching and, with Richard Arculus, offered a popular course in planetary science. In 2008, EMS was incorporated into RSES and Ross returned home to much improved circumstances as Professor Emeritus. Ross's "retirement" was certainly a success, resulting in five books and about 60 papers. Throughout his career, Ross traveled extensively. Al Hofmann once described him as "the human demonstration of the Heisenberg uncertainty principle" (Hofmann, 2003)—if you encountered him, you knew where he was at that exact moment (usually a campus, conference, or pub) but you could not predict where he might be the very next moment. For many years, he was a regular visitor at the Lunar and Planetary Institute in Houston, where he worked on many of his books. Later, he often visited and worked with his friend and collaborator Chris Koeberl, at the University of Vienna. Wherever he went, he greatly enjoyed discussing all aspects of science and was equally enthusiastic talking to a field geologist or a theoretical astrophysicist. He especially enjoyed the company of young scientists, believing that they provided the most up-to-date and least filtered views of any subject and the energy that drives the scientific process. Ross's influence on the discipline of geochemistry went far beyond his own published works. He routinely took part in the governance of both the Geochemical and Meteoritical societies and organized many conferences and conference sessions. He had a remarkable 35-yr tenure as Associate Editor of Geochimica et Cosmochimica Acta (1964–2000) working especially closely with Executive Editors Al Levinson (with whom he wrote his second book) and Denis Shaw. He also served extended terms on the editorial boards of Chemical Geology (1974–2000), Journal of Geodynamics (1982–1990), Journal of Lanthanide and Actinide Research (1984–1990), and Meteoritics & Planetary Science (1987–2002). Looking at Ross's publication list shows his remarkably wide interests and influence—from trace elements in fossils (thinking about such matters in 1956!) to the geochemistry of feldspars, tektites, lunar rocks, sedimentary rocks, island arcs, lower crustal xenoliths, and much more—all in the pursuit of better understanding the composition, origin, and evolution of the Earth's crust, the Moon, and the solar system itself. A key feature of his approach was that once he set his eye on a problem (and mostly they were important problems), he bombarded it with data (often quoting Ernest Rutherford's directive that "a scientist must make measurements") until significant progress was made, as it almost always was. Below we briefly review some of the major problems to which Ross devoted his career. Ross remained a Principal Investigator for lunar samples for two decades. He continued to make fundamental discoveries about the Moon and its place within the solar system. With Petr Jakeš, he developed the famous Taylor–Jakeš model for lunar evolution, seeing the Moon as a highly differentiated body in which mare basalts were derived from layered cumulates that formed within the mantle after crystallization of the thick anorthositic highland crust from a magma ocean. He developed models for the evolution of the lunar highlands with Ted Bence and lunar origins with Horton Newsom. The Moon remained his passion and Marc Norman was the last Research Fellow to work with him on the problem before retirement. In 2006, he led the famous Taylor Clan (Ross—Father; Larry—Son; Jeff—Holy Ghost) in an important paper: The Moon: A Taylor perspective (informally called Taylor-cubed). Ross is also renowned for his comprehensive and authoritative books on lunar science. Shortly after the preliminary examination of Apollo 11 and 12 samples, Al Levinson and Ross wrote Moon Rocks and Minerals (1971), a book Ross has described as "the pump primer." After the Apollo program concluded, he published two of the most influential books on lunar science: Lunar Science: A Post-Apollo View (1975) and Planetary Science: A Lunar Perspective (1982). It is not hyperbole to say that these books helped train an entire generation of lunar and planetary scientists. One of the lasting legacies of Ross's career was his seminal contributions to understanding the geochemistry, origin, and evolution of the continental crust. Ross was one of the first to estimate the composition of the continental crust through analyses of fine-grained terrigenous sedimentary rocks (shales; Taylor, 1964). Using rare earth element compositions of the shales, he deduced that they represented a 50:50 mixture of granite and basalt and used this mixing proportion to calculate the major and trace element composition of the bulk crust for major elements and 60 trace elements—certainly the most comprehensive estimate of its day! Shortly thereafter, in the wake of the "plate tectonics revolution" and working with Alan White, Ross noted the striking similarity between the average composition of the continental crust and andesite—one of the most diagnostic igneous rock types formed in subduction zones (Taylor & White, 1965). Accordingly, Ross hypothesized that continental crust is generated by addition of andesites at subduction zones, launching the "andesite model" of crust formation (Taylor, 1967), a model that remains popular to this day. Continuing with analyses of trace elements in terrigenous sedimentary rocks, Ross, with M.Sc. student Weldon Nance, established an iconic suite of shales (Post-Archean Australian Shales or PAAS) that have served as representatives of average upper continental crust to this day. Later, with Ph.D. student Scott McLennan, he explored how the composition of the continental crust may have changed over Earth history, co-authoring the authoritative treatise on this topic in their 1985 book 'The Continental Crust: Its Composition and Evolution.' The book has received more than 18,000 citations and is still one of the definitive statements on the topic. The Taylor–McLennan collaboration produced a total of two books and 40 papers. Ross's crustal studies included many papers on the geochemistry of andesites (launching careers of Ph.D. students Jim Gill, who himself became an authority on the topic, and later Mike Gorton and Dave Whitford) and the continental lower crust with his last Ph.D. student, Roberta Rudnick. Along the way he collaborated with many ANU colleagues and visitors in the study of andesites and other crustal rocks: Richard Arculus, Andy Duncan, Tony Ewart, Angelo Peccerillo, Mike Perfit, Dick Price, and Charlie Vitaliano. Always thinking in terms of the "big picture," Ross teamed up with Ian Campbell to write a seminal paper that explains why Earth has continents and for which one need only read the title to get the gist: "No water, no granites—no oceans, no continents" (Campbell & Taylor, 1983). This paper continues to be highly influential, having been cited 14 times this year alone. Early in his career, Ross became interested in cosmochemistry, meteoritics, and the broader aspects of planetary science. Between 1960 and 1965, he wrote on subjects as diverse as the fractionation of iron and rare earth elements in the solar nebula, chondritic Earth models, and meteorite chemistry. With Brian Mason, he characterized and classified the calcium-aluminum rich inclusions in the Allende CV3 meteorite that fell in 1969, including the notorious Group II inclusions with their bizarre rare earth element patterns indicating complex fractionation processes in the early nebula. For many years, he maintained a close collaborative relationship with Tezer Esat in ANU Physics. Beginning in 1982, he developed a classification for planetary crusts: primary, secondary, tertiary, and icy, a scheme that remains in common usage. Interestingly, after a highly detailed examination of the nature of planetary crusts in his penultimate 2009 book Planetary Crusts: Their Composition, Origin and Evolution, he concluded that even though planetary crusts can be so classified, "this does not imply any logical or inevitable sequence of development." Ross was always far more impressed with the diversity among planetary bodies than with any similarities. Once Ross formally retired, he no longer was able to "make measurements." Accordingly, during the final decades of his career, he turned his attention more fully to questions related to solar system evolution. The theme running through this work is the importance of a wide array of stochastic processes and events in planetary formation and evolution leading to the stunning diversity of bodies within our own solar system and among the rapidly increasing numbers of extrasolar planets; in one essay asking the question, "Why can't planets be like stars?" (Taylor, 2004). In his final book Destiny or Chance Revisited (2012), his examination of our solar system, extrasolar planets, and the evolution of life on Earth reinforced his skepticism of whether intelligent life ever existed elsewhere in the universe. Ross was indeed fortunate, being at the center of some of the most important and exciting episodes in the earth and planetary sciences, including the plate tectonic revolution, return of the first samples from the Moon, and discovery of solar systems beyond our own. The scientific community, in turn, was fortunate to have a geochemist like Ross apply his analytical expertise; his deep knowledge, intelligence, and judgment; and his superb communication skills to better understand the Earth and solar system in so many fundamental ways. We were also fortunate in having him as our mentor, teacher, and friend, and we will miss him greatly. The field of earth and planetary sciences has lost one of its great practitioners.