Water samples collected using the CTD rosette will be analyzed aboard the ship using a Gas Chromatograph to determine the concentrations of dissolved methane present. While high temperature vents emit a range of chemicals into the oceans that can be detected remotely using in situ sensors, only methane is enriched in all known forms of deep-sea hydrothermal systems and, hence, represents our measurement of choice for deep ocean exploration where we don’t know, in advance, what we expect to find.