John Guest (1938-2012) was a pioneer in planetary geologic mapping, contributing to the first geologic map of Mercury and the first comprehensive map of the eastern equatorial region of Mars with Ron Greeley. He participated in the Mariner 10, Viking and Magellan missions. Along with Ron, he helped to select the Viking 2 landing site. Primarily John was a volcanologist, happiest when he was in the field, especially at Mt. Etna. He founded the NASA Regional Planetary Image Facility at University College London, and taught many students there. His 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. In 1991, he was awarded the GSA G.K. Gilbert award and the asteroid 1982 HL was named Guest by the IAU. He is survived by his wife Mary and sons James and Ben.
Ellen Stofan, Angus Duncan, Rosaly Lopes and Chris Kilburn. http://www.ucl.ac.uk/es/news/esnews/2012-05-21