John is a professor at the School of Oceanography at the University of Washington. As an ore deposit geologist early in his career, he became fascinated with geological processes such as volcanism and geothermal activity that can concentrate metals. After living in and working on active volcanoes of the western Galapagos Islands, and diving to the seafloor in ALVIN, he decided to focus on active submarine volcano-hydrothermal systems along the global spreading-center network. Working with a unique set of rocks from the Mid-Atlantic Ridge, it became evident that fracturing and mineral deposition on the seafloor was identical to quartz veins beneath massive copper-iron sulfide deposits on land. The idea that placing instruments within active submarine vent systems would allow direct insights into the formation of metal deposits became a compelling focus for his research. Recognition that volcanic gases provide a significant nutrient source for the microbial communities at the base of the chemosynthetic food chain demonstrated that submarine volcanoes can support life independent of the sun. The presence of volcanoes throughout the solar system and the possibility of an ocean and volcanoes on Jupiter's moon Europa converge to make the exploration of volcanoes and life at the seafloor here on earth one of the most effective approaches human beings have of learning to explore other worlds for primitive forms of life.