William A. (Bill) Cassidy, Emeritus Professor in the Department of Geology and Planetary Science of the University of Pittsburgh, passed away quietly in his home in Monroeville, PA on March 25, 2020, at the age of 92. Bill leaves behind a deep legacy of contributions to the fields of impact crater studies and meteoritics.
While pursuing a BS in Geology at the University of New Mexico in the early 50's, Bill was made aware of Campo del Cielo and the lost Meson de Fierro iron of Argentina during a class taught by Lincoln LaPaz. A Fullbright Scholarship in Australia and a PhD from Penn State University followed, leading to a Research Scientist position at Lamont-Doherty Observatory, from where Bill would mount the first of many expeditions to the Campo del Cielo crater field. Bill's studies of the site proved of historic importance- relatively young (4000 years old), the site consists of over two dozen individual craters, most small enough to be fully excavated to reveal their original geometry and impactor trajectories. Meteorites were recovered from most of these craters, providing an early indisputable link between these two planetary phenomena. Bill's research on the Campo del Cielo site continued into his eighties, and he was loved throughout the region for his consistent efforts to include Argentine scientists, technicians, artists and laypeople in the work. Bill was involved in other seminal crater studies, including investigations of the Aouelloul and Tenoumer craters in Mauritania and the Monturaqui impact site in Chile. He also conducted pioneering research on Australasian microtektites (especially the very interesting and still not much studied “bottle green” variety), Muong Nong-type tektites, and lunar samples.
Another enduring part of Bill Cassidy's legacy is as founder of the US's Antarctic Search for Meteorites (ANSMET) program. Bill was one of the first outside of Japan to recognize that nine meteorites recovered in 1969 from the Yamato Mountains of Antarctica were the vanguard of a huge number of specimens. He persistently submitted proposals to the US Antarctic Research Program until finally funded for the 1976-77 field season, the first of several conducted jointly with Japanese collaborators. Since that time the ANSMET program has operated without interruption, sending field parties to Antarctica annually and recovering over 24,000 meteorite specimens. These include several paradigm-shifting specimens, such as EET 79001 (the first meteorite determined to be Martian in origin), ALH 81005 (the first Lunar meteorite), and many samples from rare, scientifically valuable and previously unknown classifications. The inherent altruism of the US Antarctic meteorite program, which provides samples of all recovered specimens to scientists from around the world, is a direct result of Bill's decision to give up privileged access to the meteorites in favor of a program (partnering with NASA and the Smithsonian Institution) that allows other scientists to make their own discoveries. The results have been extraordinary- a program that has lasted for generations, whose long-term impact on science easily rivals that of Apollo. Ultimately Bill led 14 ANSMET expeditions, the last in 1994. He returned to Antarctica again in the late nineties as a part of a NASA-funded Carnegie-Mellon University project to develop robotic meteorite search technologies.
Multiple honors have been bestowed upon Bill in recognition of his contributions to planetary science. He was awarded the Barringer Medal of the Meteoritical Society in 1995 for his lifelong work on impact craters and their debris. Cassidyite (Ca2Ni(PO4)2 · 2H2O) is a rare mineral from Wolf Creek Crater (found in cracks and cavities in weathered meteorites). Bill was awarded the Antarctic Service Medal in 1977, and the Cassidy Glacier, a tributary of the Taylor Glacier in the Dry Valleys region of Antarctica places his legacy firmly on the map. Asteroid 3382 Cassidy places his name in the heavens. In 2015 a hall of the Parque Campo del CieloMuseum was named in his honor.
Bill will be long remembered for his dry sense of humor, his humility, and his generosity. His legacy extends far beyond the craters he explored and the tens of thousands of meteorites his projects recovered - Hundreds of scientists forged bonds of friendship, respect, and trust as a direct result of Bill's efforts during six decades of field work, both in Antarctica and elsewhere, learning to put aside personal gains or comfort in the pursuit of science.
Ralph P Harvey, John W. Schutt, Case Western Reserve University and Christian Koeberl, University of Vienna