Allow me to introduce you all to the three main players that allow us to conduct research at hydrothermal vents: ROV Jason, AUV Sentry, and the elevator.
The hydrothermal vents that we are after are 2,500 meters below the sea’s surface. In order to study things at this depth, scientists typically use Remotely Operated Vehicles (ROVs), Autonomous Underwater Vehicles (AUVs), or Human Occupied Vehicles (HOVs). On this first cruise, we are using vehicles designed and operated by Woods Hole Oceanographic Institution, ROV Jason, and AOV Sentry.
ROV Jason is tethered to the ship via a 6-mile-long fiber-optic cable that hangs over the side of the ship. It is controlled by three pilots from large shipping containers that are fitted with many computers and television screens that provide video feed through cameras attached to multiple locations around the vehicle. The two pilots have controllers that move the robot around and operate the vehicle’s two manipulator arms, and the third pilot controls the ship's position. Jason is equipped with sonars, sampling baskets, and many camera systems. We can put our equipment needed for studying things are depth on what’s called the main basket that sits in front of Jason. There are also two smaller baskets that swing out on both sides of Jason for extra storage. Scientists usually also attach what’s called a “slurp” to the side of the vehicle. This is essentially a really long vacuum hose that allows us to suck up animals or bacterial samples into a big chamber that has 5 rotating ports.
Jason can stay at the bottom for days, but for this cruise, Jason will only be deployed for 18 hours at a time for two reasons. First, the additional cameras that the geology team has attached to Jason to take photographs from multiple angles of the seafloor and vent structures only have a battery life of 18 hours. Second, the principal investigators of the cruise have decided to alternate dives every day, meaning Jason's basket configurations need to be switched to either accommodate the biology or geology team's equipment. When Jason is requested for a cruise, Jason, wench, mini garage, control vans/containers, and equipment storage vans/containers are all shipped from port to port where the operation team flies in and helps load it all onto the ship using a large crane. You can learn more about ROV Jason here.
Sentry is a fully autonomous vehicle meaning that it can navigate throughout the water column without direct human control or being tethered to a ship. Sentry's main purpose is to map the seafloor at a much higher resolution than multibeam sonars on ships. It can also detect hydrothermal fluxes and navigate through complex terrains close to the seafloor at depths down to 6,000 meters. Sentry can produce bathymetric, sidescan, subbottom, and magnetic maps of the seafloor while also taking photographs of the benthos. Data taken by Sentry has led to very high-resolution maps that show the extent of the lava flow from the eruption in 2006 and has led to the discoveries of new surrounding mounds and vent sites.
The basket on Jason is limited in space, and often we need more equipment at the seafloor than what can fit on Jason. The elevator is a large platform with a large yellow float at the top. It is lowered into the water with a crane and free falls to the bottom while maintaining an upright position. There are holes in the platform so that water can easily flow through, and we can attach milk crates to hold different equipment. Before deploying the elevator off the side of the ship, weights are attached to the bottom so that it sinks relatively straight to the seafloor. Once it reaches the bottom, Jason can switch out equipment between its basket and the elevator. The elevator is commonly deployed so that it will land off-axis of the vents on flat basalt. Jason can also grab the top ring and carry the elevator to different vent sites, which is very helpful when working on multiple sites during one dive. Occasionally, strobes and cameras are attached to the elevator so that it can take pictures of Jason working on the seafloor. When the elevator needs to go back up, the Jason team can send a code to the elevator that tells it to start burning a cord that will release the weights on the bottom. The yellow float then carries it straight up to the surface.