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Oceanographic workhorse

The submersible Alvin prepares for a dive in September 2009. Built in 1964, the hardworking sub helped turn a sunless, freezing marine world into a new frontier. More than 4,000 dives to the seafloor have allowed scientists to discover hydrothermal vents, deep-sea minerals, and hundreds of previously unknown organisms. Learn more about Alvin with the interactive feature.

(Photo by Rod Catanach, Woods Hole Oceanographic Institution)