John Guest (1938-2012) was a pioneer in planetary geologic mapping, contributing to the first geologic map of Mercury, as well as the first comprehensive map of the eastern equatorial region of Mars with Ron Greeley. He participated in the Mariner 10 and Viking missions, as well as the Magellan mission to Venus. Along with Ron, he helped to select the Viking 2 landing site. Primarily though, John was a volcanologist, happiest when he was in the field, especially at Mt. Etna. John did his PhD work at University College London, mapping volcanic fields in Chile, including the Chao Dacite and the Upper Tertiary ignimbrites in Antofagasta Province. He then went to the University of London Observatory to work with Gilbert Fielder on lunar craters, quickly realizing that craters on the Moon are not volcanic, but impact, starting his long interest in planetary science.
He founded the NASA Regional Planetary Image Facility at University College London, and taught many students there, including Rosaly Lopes, Chris Kilburn and Ben Bussey. John founded the European Planetary Geology Consortium in 1976, along with Philippe Masson, Gerhard Neukum, and Marcello Fulchignoni, which sparked many collaborations among its members. John’s work on Mars, Mercury, the Moon and Venus, as well as his very extensive work on terrestrial volcanology, leave a rich legacy.
He had a particular talent for being able to interpret geology from surface morphology - whether in the field, from aerial photographs or planetary images. He was much loved by his collaborators and students for his kind and generous spirit, and his sense of humor, which included terrifying his students in the field with tales of hairy lava tube rats and deadly snakes camouflaging in ropy lava. He was awarded the GSA G.K. Gilbert award in 1991; that same year the asteroid 1982 HL was named Guest by the International Astronomical Union Nomenclature Committee. He is survived by his wife Mary and sons James and Ben.
Prepared by Ellen Stofan, Angus Duncan, Rosaly Lopes, and Chris Kilburn.