In the late 1980s, a remotely operated vehicle (ROV) named Jason (seen hovering over the Isis shipwreck above and being hoisted overboard off the coast of Ashkelon, Israel, in 1999, below), developed by Robert Ballard and a group of engineers at the Woods Hole Oceanographic Institution, allowed archaeologists to peer deep beneath the sea to find shipwrecks that were once far out of reach.
Jason allowed Ballard and Harvard archaeologist Lawrence Stager (shown above, at left, with project conservator Dennis Piechota) to explore two Phoenician ships (the Tanit and the Elissa) in 1,300 feet of water off the coast of Ashkelon, Israel. Jason’s cameras took hundreds of photos of the wreck sites, which were then “stitched” together to form an overall picture of the site. Ballard also retrieved objects selected by Stager with Jason’s padded grippers.
A neutrally buoyant tether connected Jason to a smaller unmanned sled named Medea, which was connected to the ship at the surface by a steel-armored electro-optic cable (see drawing above). Medea provided sufficient weight to make Jason’s long 035cable manageable, prevented wave motion from disturbing Jason, and provided lights to complement those on Jason. Medea also acted as a relay station for signals between Jason and the control room on the mother ship above.
Another generation of robotics technology is already being developed for archaeological exploration. Engineers with the Institute for Exploration, the Woods Hole Oceanographic Institution and Woods Hole Marine Systems are working on a new ROV called Hercules. This vehicle will be attached to a support ship by a steel-armored cable, which will power the ROV and carry information back to the ship. Hercules’s first mission is expected to come in the summer of 2003, when it will be used for further exploration of the Tanit.
A gantry will be erected to hold Hercules firmly in position. This aluminum frame—roughly 25 feet long, 10 feet wide and 2 feet high—will allow the ROV to work without using its thrusters, which would ruin visibility and possibly disturb the site. The frame also allows the ROV easily to move off-site and later return to the same working position.
Hercules will be equipped with several kinds of water jets, including jets with nozzles producing point-shaped and fan-shaped sprays, as well as brushes of different sizes and stiffnesses. The sediment kicked up by the water jets and brushes will be cleared away with a suction nozzle. In addition, a large “ceiling fan” propeller will push clear water downward from above to flush out the area and help maintain visibility.
Hercules will excavate selected objects with two mechanical arms. Computer-controlled sensors will allow the excavators to define areas as “off limits” to avoid damage to partially buried artifacts. The ROV’s sonar will generate bathymetric maps of the site every few minutes, so that the excavators will always know just where the mechanical arms are with respect to the site, thus preventing accidental contact.
The selected artifacts will be placed in the vehicle’s holding basket until they are brought to the surface. The final stage of the excavation will involve back-filling the site to reduce further deterioration.
Since excavation is an inherently destructive, non-repeatable means of gathering information, every effort will be made to document the work thoroughly, and only a small portion of the Tanit site will be excavated during the inaugural voyage of Hercules. We hope not only to discover more about the Phoenician shipwreck but also to learn what this new technology has to offer—what works well and what does not.