Hydrothermal exploration with the Autonomous Benthic Explorer

We describe a three-phase use of the Woods Hole Oceanographic Institutionʹs Autonomous Benthic Explorer (ABE), to locate, map and photograph previously undiscovered fields of high temperature submarine hydrothermal vents. Our approach represents both a complement to and a significant advance beyond the prior state of the art. Previously, hydrothermal exploration relied upon deep-tow instruments equipped with sensors that could locate sites of active “black smoker” venting to within a few kilometers. Follow-on CTD tow-yos could then resolve the sites of seafloor venting to length scales of less than a kilometer but rarely to better than a few hundreds of meters. In our new approach ABE: (i) uses sensors to locate the center of a dispersing non-buoyant hydrothermal plume 100–400 m above the seabed; (ii) makes high-resolution maps of the seafloor beneath the plume center whilst simultaneously detecting interception of any rising, buoyant hydrothermal plumes; and (iii) dives to the seafloor to take photographs in and around any new vent site to characterize its geologic setting and reveal the nature of any chemosynthetic ecosystems it may host. By conducting all of the above under long-baseline navigation, precise sites of venting can be determined to within 5 m. Our approach can be used both to address important scientific issues in their own right and to ensure much more efficient use of other deep-submergence assets such as human occupied vehicles (HOVs) and remotely operated vehicles (ROVs) during follow-on studies.