Right: A closeup of the primary tool used to map hydrothermal plumes. A ring of plastic sampling bottles surrounds the CTD. The bottles are closed on command from the ship, usually when a scientist monitoring the sensors sees strong evidence of a plume. The blue frame holds a unique PMEL-developed in-situ chemical analyzer, capable of real-time chemical analyses of iron, manganese, and other plume tracers. Left: Scientists deploy the CTD. Image courtesy of Submarine Ring of Fire 2002, NOAA/OER.