Born in Durham, Ontario, Canada, Mac grew up in Saskatchewan and studied Engineering at the University of Saskatchewan (B.Sc. 1961). He turned toward geology after carrying out fieldwork for a mining company. He received his Ph.D. from Johns Hopkins University in 1968. After a brief postdoctoral appointment at the University of California at Los Angeles, he joined the faculty at Brown University in 1970 and taught courses on field geology, geologic hazards, volcanology, meteorites, and igneous petrology. Mac retired in 2006 but continued to engage in advising and research at Brown until the very end. His last experiment was run on September 4, 2023.
Mac had a distinguished career and was a world expert on volcanic rocks from Earth, Mars, and the Moon. His early-career scientific interests were shaped by two events on the world stage: the NASA Apollo program and the 1980 eruption of Mount St. Helens. The latter motivated a sequence of pivotal contributions, culminating in an integrated experimental and field approach for placing crucial constraints on the environmental conditions at which magmas were stored underground prior to eruption and the rate at which magma ascends to the surface. He applied this approach to eruptions of Mount St. Helens, Soufriere Hills Volcano, El Chichón, Pinatubo, Campi Flegrei, Novarupta, Unzen, Mazama, Black Butte, and other volcanos. His method was embraced by the volcanological community and has become a part of ʻpetrologic monitoring’ of restless volcanoes.
The return of Apollo samples inspired Mac to embark on a series of experimental investigations of phase equilibria of lunar magmas. This led to fundamental contributions to our knowledge of silicate liquid immiscibility, the origin of lunar granite, the differentiation of lunar magmas, and the solubility of sulfur in mare basalts. He played a pivotal role in the study of the origin, speciation, and concentrations of volatiles in the lunar interior. While continuing to work on magmatic processes on the Moon and Earth, Mac studied Martian meteorites in his later years, exploring their petrogenesis, oxidation state, surface alteration, and relationships to spectral properties of the surface of Mars, which is crucial to the interpretation of remote sensing data from Mars.
Mac was a Fellow of the Mineralogical Society of America. He served as Chair of the Department of Geological Sciences (1986-1991), Co-Editor-in-Chief for the Journal of Volcanology and Geothermal Research (2009-2012), and as chair or member on countless NASA, AGU, and University committees and panels. Mac was generous and supportive of his colleagues and students. He fostered a warm, collaborative research group and mentored dozens of students and postdocs who went on to NASA, university faculties, the United States Geological Survey, federal labs, and industry. He was keen to lead geological field trips and was an avid participant in the Lunar and Planetary Science Conferences. His legacy of science and mentoring extends to all corners of the Earth and across the solar system.
Mac is survived by his wife Helen, and three sons, Brian Rutherford, Tim Rutherford and his wife Lisa, and Greg Rutherford and his wife Natasha, as well as his three grandchildren, Brooke, William, and Cameron, and his two siblings, Kay Hilborn and Don Rutherford.
A celebration of Mac’s life and contribution was held on November 15th. Learn more.
