For this mission, German and his colleagues used the plumes in the search for hydrothermal vents, employing sensors mounted on equipment and robotic vehicles to track the chemicals back to their source. This expedition used a CTD (conductivity, temperature, and depth) array augmented with sensors to detect suspended particles and anomalous chemical compositions (the latter sensor courtesy of Ko-ichi Nakamura from AIST in Tsukuba, Japan) mounted on both a water sampling rosette and the hybrid vehicle Nereus, a deep-diving robot that can operate in both in tethered and free-swimming modes.
Using the CTDs and Nereus in "autonomous" or free-swimming mode, the team sniffed out deep-sea plumes originating from the seafloor hydrothermal vents. Using a combination of shipboard and shore-based analyses of water samples for both their chemical and microbial contents, the team was then able to track the plumes toward their sources as well as to determine the likely nature of the venting present at each site. The ultimate goal was to switch Nereus into tethered or "remotely operated" (ROV) mode during the latter stages of the cruise and dive on each vent site to collect samples using Nereus' robotic manipulator arm.
"Part of the excitement of this NASA-funded project was the success of deploying a full-ocean-capable tethered vehicle to search for vents at 5000 m from the R/V Cape Hatteras, which, at 41 meters in length, is one of the smallest ocean-going ships in the national fleet. This is a first," said Cindy Lee Van Dover, co-author on the study and director of the Duke University Marine Laboratory.
The first two sites the team identified are extremely deep and were named Piccard and Walsh in honor of the only two humans to dive to the Challenger Deep the deepest part of the world's ocean. The plume detected at the Piccard site 800 meter
|Contact: Stephanie Murphy|
Woods Hole Oceanographic Institution