Oceanographic Tools: Jason II
Jason/Medea is a remotely operated vehicle (ROV) system that allows scientists to survey and sample the seafloor without leaving the deck of their ship. The ROVs are named for the adventurous sea captain of Greek mythology and his wife.
Jason, which is about the size of a minivan, is the main vehicle. It is equipped with sonar imagers, water samplers, video and still cameras, and lighting gear. Its manipulator arms can collect samples of rock, sediment, or marine life. Medea, which is about the size of a Mini Cooper car on its side, travels behind and above Jason. Medea’s lights illuminate the area around Jason and its cameras help the Jason pilots—who are on the ship at the surface, a mile or more above—guide the ROV.
Jason and Medea are linked to the ship by a tether that is 10 kilometers (6.2 miles) long and less than an inch in diameter. The tether carries fiber-optic lines that deliver electrical power and instructions from the ship to the ROVs, and data, photos, and video from the ROVs to the ship.
Jason and Medea are linked by a tether that is just 35 meters (114 feet) long. Engineers in the Deep Submergence Laboratory at WHOI designed the Jason/Medea system with two “bodies” to protect Jason from movements of the ship at the surface. While the ROVs are on their mission, the tether connecting Medea to the ship is taut, but the one that links Medea and Jason remains slack. This allows Medea to serve as a shock absorber: If waves at the surface move the ship up and down, Medea will rise and fall, but Jason can continue to work undisturbed.
Jason is highly maneuverable. Its six thrusters give its pilots precise control in the vertical (up and down), longitudinal (forward and backward), and lateral (left to right) directions. It can hover a meter above the seafloor, nose into deep crevices, and pluck samples from a spot pinpointed by scientists on a ship two miles above.
The Jason pilots and scientists work from a control room on the ship to maneuver the vehicles and monitor Jason’s instruments and video. They follow the action at the seafloor on eight video screens, three from Medea and five from Jason.
The samples Jason collects can be placed in a basket on the vehicle, but the basket fills up fast. Returning to the ship to empty the basket and then diving back to the seafloor takes many hours—time that could be better spent gathering more samples. So the Jason engineers have devised ways to keep the ROV at the seafloor longer. Now, Jason’s manipulator arms can place samples on an “elevator,” a weighted, deep-sea platform that the team drops from the ship and that falls to the bottom. When the 6-by 6-foot elevator is loaded with samples, the Jason team on the ship signals it to drop its heavy weights. The buoyant elevator then rises to the surface, where scientists retrieve its valuable cargo of samples. All the while, Jason continues working a mile or more below.
The average Jason dive lasts 21 hours, but the elevator has made it possible to do much longer dives. On a recent mission, Jason and Medea stayed down for more than 100 hours (more than 4 days)!
Jason was first launched in 1988 and is now in its second generation, with a sturdier, more advanced vehicle having been launched in 2002. The system has been used for hundreds of dives to hydrothermal vents in the Pacific, Atlantic, and Indian Oceans. In 2010, it provided the first live look at an exploding underwater volcano.
The Jason/Medea system has also had a successful career in underwater archaeology. A prototype version named Jason Jr. was used to survey the wreck of RMS Titanic, and the fully developed Jason visited a 1,600-year-old Roman trading ship in 1989.
Medea and Jason are designed to operate to a maximum depth of 6,500 meters (21,385 feet), which gives them access to most of the seafloor. They can be operated from a variety of vessels.