The robotic undersea vehicle Puma went plume hunting Monday afternoon. It was programmed to descend more than 3,200 meters (2 miles) below the ocean surface and fly over an area about 2 by 2 kilometers (1.25 by 1.25 miles) wide. At the same time, it flew up and down roughly between 100 and 400 meters (325 to 1,300 feet) off the seafloor. At that depth, other researchers aboard had found evidence of waters that were rising from seafloor hydrothermal vents and spreading out into a plume. Equipped with sensors to detect temperature, chemical, and particle signals, Puma set out to help pinpoint the plume. Mission accomplished. It was ready to resurface at about 7 a.m. Tuesday.