Archaeologists return to Antikythera with advanced ocean technology
When sponge divers first chanced upon the shipwreck off the Greek isle of Antikythera in 1900, they couldn’t have known that it would become the richest ancient shipwreck ever discovered.
But they soon found that this was no ordinary wreck, as they pulled up jewelry, coins, glassware, and life-size bronze and marble statues now housed in the National Archaeological Museum in Athens. The pièce de résistance was the unique and mysterious Antikythera Mechanism, a complex clockworks device, often called the first known computer, whose gears encoded the movements of the five planets known at the time, phases of the moon, and eclipses.
More than seventy years later, Jacques Cousteau returned to the wreck. His team found hundreds more artifacts, as well as the remains of four people, including a woman. But the Cousteau expedition merely unraveled the mystery a little further. They apparently explored only the galley and stern passenger compartment, leaving the main compartment untouched since 1901.
Next week a multinational team from the of the Hellenic Ministry of Culture and Sports’s Ephorate of Underwater Antiquities (EUA), Woods Hole Oceanographic Institution (WHOI), and the Australian Centre for Marine Robotics will return to the wreck site to investigate what else it may still hold. To a Clive Cussler-like setting, they will bring James Bond-like technology: underwater robots to try to map and photograph the site, rebreathing diving gear to stay down longer, and a new robotic Iron Man-like diving apparatus called an Exosuit, which allows divers to stay under water for hours and descend to 1,000 feet. This will be the suit’s grand, experimental debut in the world of archaeology.
The team plans to explore sonar targets that could be colossal statues and another wreck nearby that could have been the Antikythera ship’s traveling companion. Many hope to find the head of a seven-foot-tall headless statue of Herakles salvaged in 1901, as well as still-missing parts of the Antikythera Mechanism, “which, to my mind, is the most astounding archaeological artifact ever discovered anywhere on any site,” said WHOI scientist Brendan Foley, who is co-director of the expedition with Theotokis Theodoulou and Dimitris Kourkoumelis of the EUA. Foley and colleagues have spent almost a decade experimenting with new marine archaeology technologies and approaches carefully tailored to the tempermental coast where the shipwreck lies.
The old-fashioned way
Foley’s collaboration with Ephorate of Underwater Antiquities began in 2005 when Katerina Delaporta, then the ephorate’s director, invited a team from WHOI and the Massachusetts Institute of Technology to help survey a 4th-century-B.C. merchant shipwreck. It was situated too deep for conventional diving, so the team turned to robots. The researchers chose an autonomous underwater vehicle (AUV), since it was untethered, suitable for shallower depths, easily deployed from smaller watercraft, and had a low operation cost compared to other robotic options.
The project’s scientific yield was bountiful: high-quality mapping and extensive photography revealing 250 large clay storage vessels called amphoras. The team even tested two of the empty amphoras for trace DNA and revealed evidence of the ship’s cargo: olive, oregano, and resin from a Mediterranean shrub used to preserve wine.
Around that time Foley caught wind of “the list.” Compiled by Greek government officials, it contained hundreds of known or reported wrecks within SCUBA-diving depth limits. “It occurred to me that in between the big projects with the robots, we could make a lot of hay by doing diving work on these reported, but not yet investigated, sites just with regular SCUBA,” Foley said.
And hay they made. In 2008, the team investigated ten ancient wrecks in ten field days, all without the help of AUVs.
As the Greeks grew confident in their relationship with the WHOI team, they invited more collaborations to explore wrecks. A new ephorate director, Aggeliki Simossi, continued the relationship started by her predecessor. She invited Foley to investigate the wreck at Antikythera, a holy grail for underwater archaeologists.
Located in an ancient high-traffic shipping lane at the crossroads of the Aegean and Mediterranean Seas, the wreck site has a syzygy of problematic features. It was too shallow to warrant a sub or a standard remotely operated vehicle (ROV), which require larger ships. It was situated near steep underwater cliffs, putting it an angle that makes it hard for laterally-moving AUVs to survey with sonar. “I’d talked to all the vehicle engineers around here and none of the robots were designed to do this site,” Foley said.
Ed O’Brien, WHOI’s dive safety officer, was called in, and as he began examining the site, it became clear: “They’d have to do things the old-fashioned way,” O’Brien said. “They’d have to get in the water.”
Still, at more than 200 feet deep, the Antikythera site remained out of reach of conventional SCUBA diving.
The right tool for the job
Back in 1900, it is a wonder that the original Antikythera divers salvaged anything at all. They shared a single diving suit with lead boots and a brass helmet pump-fed air through a hose. Divers took turns of ten minutes twice per day.
“Despite the divers’ great skill and personal bravery, two men were severely injured and another diver lost his life,” according to the research team’s website. “By the end of the operation in September 1901, only five men were still fit to dive.”
By the time of Cousteau’s expedition, SCUBA gear had arrived, but that still allowed his divers only ten minutes on the bottom to work. And then there’s the weather factor.
O’Brien had watched the old TV show on Cousteau’s expedition to Antikythera and saw scenes of Cousteau’s ship Calypso surging ominously close to the rocky coast. The local meltemi winds had provoked the sea into jagged mounds. Every wave threatened to intimately introduce ship to rocks. These meltemi winds, infamous for rising swiftly and suddenly, have been a scourge of ships for millennia.
“If the weather starts getting rough, it’s quite a dodgy operation,” O’Brien said. On regular SCUBA gear, if the research team had forty minutes of underwater working time, they could be in the water up to eighty minutes. The latter half of the dive would be spent in a mandatory slow rise to the surface called decompression.
When divers breathe from their tank at depth, gas from their lungs eventually dissolves into their tissues. Without decompression, bubbles could form. They can expand rapidly and perhaps lethally at lower pressures at the sea surface. The slow ascent gives the body time to expel the bubbles into the bloodstream and out the lungs.
Unfortunately, if weather picked up, the boat could not wait a leisurely forty minutes to depart the turbulent waters and looming rocks. To explore the Antikythera wreck, O’Brien needed to find something beyond typical SCUBA gear. The search brought him out of the realm of recreational, and into commercial and military diving.
The rebreather
O’Brien considered many dive technologies: surface-supplied air and multi-tank technical diving, but neither satisfied his not so modest wish list: a longer time span for working on the bottom, the capacity to travel deep, logistically unfussy equipment with simple upkeep for use in a remote area, and the ability to surface at a moment’s notice should weather turn sour. It was a tall order, but the cocktail of needs could be met with a device called a closed-circuit rebreather.
Regular recreational SCUBA diving involves breathing air in from a tank and back out into the water. In an average breath, divers take in about twenty-one percent oxygen, but only use about five percent of it. What if divers could harness the leftover sixteen percent? What if they could re-breathe it?
Rebreathers are based on that theory. They work by turning divers’ exhales into inhales—using a chemical filter to “scrub” out carbon dioxide, a waste product of our metabolism, in exhales.
But rebreathers had a bad reputation. For the better part of this century, rebreather divers’ accident rates were less than encouraging.
“There was some mystique about the rebreather as a type of a death trap,” O’Brien said. “But we took away the curtain and tried to see if it was the right thing for us.”
It was. Decades of technological improvement and diver training overhauls had increased rebreathers’ reliability.
In 2012, the research team went out to the Antikythera site with rebreathers. By design and default, the expedition was as much a technological test bed as it was an archeological project. Rebreather training ran for two weeks in Greece. Half the team collected data while the other received rebreather instruction, so as not to squander precious days in the field.
“Once we got trained on the rebreathers, none of us wanted to go back to SCUBA,” Foley said. By re-using oxygen, divers didn’t need to carry as many gas tanks and could remain under water for up to three hours. The rebreathers regulated gas levels, allowing divers to breathe more oxygen and avoid a buildup of nitrogen in their bloodstreams. This alleviated “narcosis,” a sort of drunk feeling and post-dive fatigue caused by elevated nitrogen levels. Most important, it reduced the need for divers to surface slowly to decompress nitrogen. If they had to, they could surface fast, before the meltemi even had time to get their pants on.
“This is a game-changer for us,” O’Brien said.
Orbiting Antikythera
Now that they had increased their underwater work time, the question became what to do with it. “We started to think seriously about how to get better coverage, get more productivity for each of our dives,” Foley said. In previous seasons, they had tried to cover more area by using jetpack-like thrusters mounted on their conventional scuba tanks, but the batteries gave out in forty minutes, long before their oxygen did.
“They were a good idea,” O’Brien said, “but they weren’t really the right tool.” Phil Short, their technical diving instructor and Kevin Gurr, managing director at VR Technology, recommended trying a diver propulsion vehicle (DPV), a torpedo-shaped scooter that pulled the diver through the water.
The team’s first DPV trial was an attempt to cover roughly three miles. The dive took them an exhausting three hours and ten minutes, the last half of which was spent mostly, “gritting our teeth and getting through it,” Foley said.
Designed to be hands-free, the scooter was secured to the diver by a strap running between the legs. This meant that divers’ pelvises were constantly being pulled toward their heads, compressing their backs.
“If you’re doing something and you start to feel miserable at it, then you are going to be less efficient,” O’Brien said. But a ninety-minute dive with DPV still covered more ground than a three-hour dive sans DPV, so using DPVs for shorter timespans provided the most efficient balance.
Two or three dive teams rotated into the water throughout the day. Team one would send up two buoys once they had been in the water 90 minutes, which told the next team where to pick up where they had left off.
“It really worked out great,” Foley said.
So great that the team circumnavigated the 21-mile coastline of Antikythera in eight operational days. Between the rebreathers and the scooters, “it really was quite a change in our productivity curve. We were able to do things under water that I don’t know that anybody outside the military can do,” Foley said
2014: the return to Antikythera
For this year’s expedition, the team will continue their technological trail-blazing. They have assembled a small well-equipped army, a characteristically ambitious plan, and a shopping list that would make Cousteau jealous.
First, before they disturb the site in any way, the Australian team will dispatch AUVs to make precise maps of the wreck site. During the 1900-01 salvage operations, several colossal boulders were dragged into deeper water to get at Antikythera’s bounty. But one boulder was brought up on deck, almost sinking the ship in the process. Cleaning revealed it to be the statue of Herakles, now in the National Archaeological Museum in Athens. During the 2012 expedition, the team used sonar to identify targets whose whereabouts matched the presumed locations of the exiled “boulders” which could be more statues. A Hellenic Navy ship on site will have a five-ton-capacity crane to hoist heavy objects from the deep.
After a week of AUV work, ten rebreather divers, including six Greek active-duty Navy SEALS, will comb seafloor sediments and the wreck with metal detectors to home in on possible archaeological targets. The divers will then excavate several test trenches based on initial surveys.
Finally, the team plans to bring in the Exosuit, which allows divers to go on deeper and longer dives. It has thrusters and articulated joints that make maneuvering easier and cameras and a fiber-optic tether that delivers live images to the surface. Inside the Exosuit, the pressure is maintained at one atmosphere, so divers can surface quickly if they have to. With the Exosuit, divers can explore the exiled “boulder” targets that lie in about 260 to 460 feet of water, beyond the reach of SCUBA divers, even those using rebreathers.
The Exosuit has never before been used for marine archaeology, so the expedition will experiment with its capabilities. Ten team members are certified to dive the Exosuit. “We hope to dip the Exosuit at least twice per day, every day the system is available and the weather cooperates,” Foley said.
The team has many mysteries to solve. The Antikythera wreck clearly was a luxury ship and, as O’Brien, who has a background in maritime casualty response pointed out to Foley, luxury ships don’t travel alone, especially in a time when piracy was common.
In 2012, the team found evidence of a second wreck about 800 feet south of the Antikythera wreck with the same sort of amphoras and anchor. “It looks like it is from the exact same time period,” Foley said. Chemical analyses of lead in the anchor and Antikythera’s anchor would reveal their sources and help determine if they are sister ships.
“Each shipwreck is a book,” Foley said. Each artifact is a page with which scientists can piece together stories about agriculture, technologies, economies, art, and geopolitics of the past. Applying modern technology, his team is striving to advance our ability to reconstruct the lost history of civilization on our planet.
Sponsors of the Antikythera expedition include: Hublot, official diving watch; OTE–COSMOTE, official telecommunication sponsors; Aikaterini Laskaridis Foundation, academic partner in Greece and support in-kind with vessel GLAROS; Swordspoint Foundation, benefactor; J.F. White Contracting Co., provider of Exosuit; Mr. and Mrs. James H. Orr, Jr., benefactor; family of Michael Dubno and Loren Blackford, benefactor; Richard and Laetitia Garriott de Cayeux, benefactor; private sponsors of Woods Hole Oceanographic Institution; Domestic Property Committee of Kythera and Antikythera.
Source : www.whoi.edu
