Did You Know?
ROVs can travel much deeper than a human diver and stay down for much longer without concerns about air or decompression.
A deep dive
ROVs are categorized into classes based on size, depth capacity, and horsepower; as with any tool, the right ROV for the archaeological job is dependent on the environment and the goals of the project.
Going down — like way, way down? Work-class ROVs, like the one used as part of the 2007 “Mardi Gras” shipwreck project in the Gulf of Mexico, dwarf their operators. Huge, heavy, and expensive, the minivan-sized ROVs can be equipped with a variety of manipulators and go to depths of 10,000 feet or more. A smaller ROV might sound more agile and therefore easier to drive, says Mark Gleason, an ROV pilot and an assistant professor specializing in marine education at Michigan’s Grand Valley State University. But the heft of the work-class ROVs helps keep them on course when tugged about by strong ocean currents in deep-water environments.
In the case of the Mardi Gras shipwreck — named after the nearby oil and gas pipeline system — the mystery ship rested 4,000 feet below the surface, off the shore of New Orleans. It was, at the time, the deepest wreck explored in the Gulf.
Led by Texas A&M University with a team of more than a dozen archaeologists, plus a film crew, ROV pilots, and support staff, the Mardi Gras project’s goals were to record the site and recover artifacts for analysis. Work was underway 24 hours a day, live-streaming to a bullpen of monitors on the ship so several sets of eyes were always on the work being performed.
Because recovering artifacts was a primary goal, the project’s work-class Triton ROV was modified to wield unique retrieval tools: a suction package with a filter, baskets and containers, shovels and brushes, pincers, and claws. It was painstaking work — archaeologists aboard the ship relayed instructions to the ROV pilots, who then had to perform the delicate maneuvers to pluck, scoop, or suck coins, buttons, tools, dishes, bottles, sand-glasses, weapons, and even the ship’s stove from the ocean floor.
“Not one artifact was destroyed,” says Peter Hitchcock, who was involved as part of A&M’s Department of Oceanography. “That’s pretty remarkable when you consider the glass and china we recovered.”
Still, “most archaeology is tactile,” notes nautical archaeologist Ben Ford, part of the project’s team through A&M’s Department of Anthropology. “You handle artifacts, rotate them, squint at them, look at them under microscopes.” To watch in 2D as the artifacts were recovered was tricky, he says, as was relaying all his thoughts and directions to the ROV pilots rather than performing the actions himself.
Hitchcock disagrees. “It’s not really different,” he says. “Every shipwreck has a story, and you want to know what it is. The ROV is simply a tool to get to the artifact to get to the story.”
And the Mardi Gras ship’s story?
The artifacts the ROV recovered were traced to manufacturers in Great Britain, France, Mexico, the U.S., and Germany, and dated; based on the age and availability of the items on board, researchers placed the wreck between 1808 and 1820. More importantly, the project gave the team an opportunity to experiment with the ROV as a deep-water archaeological tool.
“As nautical archaeologists, we realize more and more that the tools ocean explorers were using, we could use too,” Hitchcock says.