Two thousand years ago a storm drove a Roman ship against a sheer rock wall on the north side of the remote Greek island of Antikythera. The boat sank, along with tons of treasure: coins, gold jewelry, dozens of large marble and bronze statues, and an extraordinary, bronze clockwork device now counted as the first analog computer.
The wreck lay at the sea bottom, 165 feet down, untouched until 1900, when one day sponge divers came upon it. The divers were equipped with little more than a helmet and a long hose to the surface for air; they struggled just to reach the decayed vessel. One of them died, and two others were paralyzed.
The next expedition did not come until 1976. Jacques Cousteau and his crew explored the site using standard scuba gear. To leave time for the ascent, which had to be slow to avoid “the bends”—the fast expansion of nitrogen in the body that can destroy nerves and kill—the divers could stay on the bottom only for a few precious minutes during each dive.
Limited time on the seafloor evaporated last October during a new expedition to Antikythera. Explorer Phillip Short stepped off the stern of a borrowed boat, Petros Iro, wearing a computerized breathing system with multiple tanks called a closed-circuit rebreather. The gear cut down on the rate at which nitrogen builds up in the tissues, allowing him to prod the shipwreck for an hour and a half before turning back. The return ascent still had to be slow after such a long submersion; Short brought along a magazine so he could read at the planned stops upward. During two weeks of dives, Short and his fellow explorers uncovered all kinds of encrusted objects, from double-handled ceramic jars to a seven-foot-long bronze spear.
After Short and others had made several round-trips, Edward O'Brien of the Woods Hole Oceanographic Institution put an even more exotic technology to the test. Onboard a Greek navy ship, Thetis, he climbed inside a glistening, muscle-bound shell called the Exosuit, making him appear like something between Iron Man and Buzz Lightyear. At 10:40 on a sunny morning he was lowered from Thetis into the surf and descended to 200 feet, just adjacent to the wreck site. The suit maintains surface air pressure, allowing divers to stay submerged for many hours and to come right back up, without the need to stop ... or read. “You don't have any sense of pressure or depth,” O'Brien exclaimed after his exuberant return to the ship. “Fifty feet feels the same as 200 feet, except maybe it's darker at 200.”
The equipment that Short and O'Brien used is emblematic of the powerful technologies that marine scientists now have at their disposal. They are quickly and cleverly adapting innovations from other professions to bolster their own capabilities. The Exosuit, for example, was designed for workers who have to tread through water and sewer tunnels that can be miles long, but now J. F. White Contracting has altered it for ocean archaeology.
As a result, many valuable sites that have been difficult to reach are now opening up to exploration, yielding finds in a matter of weeks that might have taken years not long ago. At Pavlopetri, Greece, for example, the site of the oldest submerged harbor town ever found, divers swimming just a few feet under the surface pushed a small optical mapper that took thousands of digital, three-dimensional photographs. Software stitched them together, revealing submerged houses, streets, trading centers and tombs that made up a full, shore-side town from 4,000 years ago. At excavations near the Egadi Islands off Sicily, where in 241 B.C. Roman and Carthaginian ships sank during the last battle of the first Punic War, sonar scanners pinpointed more than a dozen submerged wrecks. Robot submarines with strong, nimble pincers snared a variety of battle gear and raised it to the surface.
I spent more than a week with divers and expedition members at Antikythera, shuttling back and forth between the boats and the shore. On one evening Brendan Foley, the Woods Hole marine archaeologist who led the excursion, sat for an interview at a breezy cliffside storeroom above the docks. Behind him on a wall was a trophy of the first few days—a large printout of the first photomap ever made of the site. “We are at the beginning of a new era,” he told me.
“We can cover more area, faster and more accurately. And remember,” he continued, “shipwrecks are archaeological sites frozen in a moment of time. They are unlike land sites,” which are constantly raided, rebuilt and ravaged in other ways. Bronze statues, for example, were routinely melted in bygone eras to make cannons, but on the ocean floor they can be found whole; most of the best ancient statuary in museums has come not from land but from the sea.
Because time stops on shipwrecks, objects untouched for thousands of years can provide great cultural and scientific insights into past societies. The chance of realizing that promise is greater now. “It used to be that in marine archaeology, working underwater was a problem,” says Jon Henderson, an archaeologist at the University of Nottingham in England who co-led the Pavlopetri expedition. “It's no longer the problem. We've moved on.”
Automapping at Antikythera
The new technology is so empowering that it is launching grand new dreams. One of them is mapping entire regions of deep seafloor relatively quickly, using a small fleet of autonomous underwater robot vehicles. Foley, for one, would like to chart the entire Aegean Sea bottom between Crete and the Greek mainland. The area has been a busy maritime traffic corridor for 5,000 years, and sonar-toting robots should be able to readily see bounty on the bottom. In one experiment, Foley found, confirmed and videotaped 10 possible shipwrecks in just 10 days.
In the past, marine archaeologists have had to painstakingly map out a prospective site using hand tools: tape measures and wood frames with string to make grids that indicated where objects might lie and how they might relate to one another. Mapping or digging deeper than 100 feet quickly became problematic because divers could stay submerged for only a few minutes before having to ascend again.
At Antikythera, a team of engineers at the University of Sydney lowered a tandem of yellow torpedoes from the stern of a modest boat into the clear Aegean waters. The researchers then let the robot loose to find the bottom. Team leader Oscar Pizarro did not have to operate the autonomous, underwater vehicle, named Sirius, because it followed a preprogrammed mission on its own. Sirius glided 10 feet above the wreck site, making 40 parallel, overlapping runs—lawn-mower-like—firing strobe lights along the way to brighten the bottom for its stereo cameras. The vehicle knew its location to within three feet or so, thanks to a GPS signal, but it obtained far more precise location information for every rock, dip and protrusion by combining the data from each image with data about its own speed, depth and orientation. Each bit of information was used to make corrections and adjustments. If in one image there was a shadow behind a rock, for example, another image from another angle filled the shadow.
Although one three-hour session, followed by a few more hours of computer work, would have been enough to take the old wreck's full portrait, the team did two more passes for additional accuracy. The final, composite image contains 50,000 individual photographs, each accurate to tenths of an inch. And the image is three-dimensional, so it can be tilted and viewed from the side.
Team member Stefan Williams says that a survey of similar scope done elsewhere a few years ago took more than a month to complete. His group did it three times, in a single weekend.
Breathe and Rebreathe
Once the mapping was finished, divers could descend to specific spots, repeatedly if desired. The sponge divers who did reach bottom in 1900 spent barely three minutes there, although even that was enough to recover an ancient analog computer, now called the Antikythera mechanism. Deep diving is dangerous because the great water pressure compresses gases in human tissue to a mere fraction of their usual volume. The body's cells compensate by using air from tanks breathed in by divers to pack tissue and resist the pressure. That means the body must cope with a large volume of air, mostly nitrogen. The longer a person is underwater, the more the gases build up.
The biggest threat is that when divers start to ascend, the gases in the tissues can release and expand, like fizz from an opened soda bottle. It is essential that divers rise slowly so the gases escape slowly; if they emerge too fast, they can form bubbles in the blood that can block circulation in small blood vessels and cripple nerves and organs. Nitrogen is particularly troublesome.
On the cramped dive boat, Short wrestled with about twice as much gear as he would on a regular scuba mission, twisting and turning to get all of it on his body. Instead of a simple metal bottle of air, as in standard scuba, the rebreather draws from two cylinders that Short pulled up onto his back, one containing oxygen and one a “trimix” cocktail of helium, oxygen and nitrogen. The rebreather takes the diver's exhalations, scrubs out the carbon dioxide, then injects oxygen to replace what the diver has used. Software monitors the oxygen level, in effect creating a custom mix of gases for all phases of the dive.
Each evening there was also an hour's work dismantling, cleaning and reassembling the high-tech equipment. “I admit to being completely OCD about this stuff. It's got to be just right,” Short said, as he knelt beside the tanks and the wrist-mounted computer display that controls them. “When everything's working well, it's no problem. But you have to be alert and prepared for what to do when something goes wrong, say, with the electronics. That's what you need training for—possible emergencies.”
Less high-tech but very helpful during the early dives was an underwater metal detector. After 2,000 years, the wood parts of ships have largely dissolved, and most artifacts have been buried in sand and sediment, many of them “concreted”—encased in calcium carbonate and other minerals so they look like big, white rocks.
Just as on land, the wandlike detector sounds off with a whine when it finds a metallic object. In the first few days, the divers detected several strong signals and laid down stones painted yellow to identify the hotspots for later searches.
After waiting out a few subsequent days of 30-mile-an-hour winds and eight-foot waves, diver Alex Sotiriou went back to the tagged areas and began to dig. Here is where the disadvantages of water turned to an advantage. Dry ground is often hard, demanding that land archaeologists slowly pick away at a site with shovels, trowels and finally brushes to unearth artifacts. But at sea the “ground” is soft and easily swept away by the pass of a diver's hand. Trenches can be dug with ease, and suction hoses can draw up silt and sand and dump it elsewhere. With a single swoosh of his glove, Sotiriou whisked away inches of silt. Another swipe, and the butt end of a bronze spear appeared. He kept fanning along the shaft and finally found the large, sharp tip. In all, the intact spear was seven feet long.
Archaeologists on the team think that the spear is too heavy to have been a weapon and that it was probably once in the grip of a great, bronze warrior statue still buried at the site. The divers also brought up a red terra-cotta jug about a foot and half high, probably used to serve wine. They found a bronze ring for tying up the ship's rigging, as well as two decorative rings from a Roman bed. The divers hauled up the smaller objects in handheld bags. For larger items such as the spear, they unpacked flat tubes they had carried down with them, inflated them with air from one of the breathing tanks and tied them on the objects, gently floating them up to the boat.
The most intriguing discoveries, however, were 600 feet away—far enough from the main wreck that the divers think they found a second ship, which might have been traveling with the first. There they uncovered a second anchor, a piece of lead pipe that might have been from the vessel's bilge pump, and a stack of jars that looked as if it had never been disturbed. Their shapes and markings indicated that they had come from four ports: Pergamon, Ephesus, Kos and Rhodes—the same four varieties that had been found on the main ship.
Excited when the origins were confirmed onshore, Theotokis Theodoulou, an expedition leader at the Greek Ephorate of Underwater Antiquities, declared that “this place still has many secrets. And we want to come back again and again to uncover them.”
The Excellent Exosuit
Progress on the next trip, if it happens, could be quicker still, thanks to the most talked about new technology that was rolled out during the Antikythera dives: the Exosuit.
After two weeks of delays because of nasty winds, on October 7 O'Brien, inside his Exosuit, was swung off the deck of Thetis and lowered by cable into the surf. It was the first mission for the suit, built by Nuytco Research. “The first time in saltwater,” exclaims Jim Clark of J. F. White Contracting, which owns the armor.
When O'Brien was in the water, operators detached the cable, and he dropped to the bottom 200 feet below, close to the wreck. There he put the suit through its paces. It has 18 flexible joints that allow natural movements of the arms, legs and torso. If needed, O'Brien could kneel down, lie prone on the ocean floor and contort into the many postures working divers find themselves in.
The real excitement came not from the suit's strength and nimbleness but from the fact that it keeps its human occupant at surface pressure all through a dive—no compressed gases in the body and no decompression sickness.
After coming back to the surface in mere minutes and climbing out of the suit on deck, O'Brien told me while standing at the boat's railing that the experience was completely unlike scuba diving. Officer Fotis Lazarou of the Greek navy piloted the suit down to 200 feet later the same day.
On land the suit, made of metal and synthetic materials, weighs more than 500 pounds, but it is light as a feather in the water, almost neutrally buoyant. It can keep a diver at surface air pressure down to 1,000 feet, greatly extending the depths at which humans can work without being trapped inside a submersible.
Archaeologists are already talking about using the Exosuit to search large areas of undisturbed sea bottom—below the depths that fishers trawl, about 300 feet. On future dives the suit will have a specially designed suction hose that will allow its human pilot to vacuum up sand and silt from a wreck for hours at a time. Researchers hope to use the Exosuit on a new mission this year to continue the Antikythera excavation.
Prototype at Pavlopetri
Earlier campaigns set the stage for Antikythera. The precursor to the Sirius robot vehicle was actually developed for the Pavlopetri expedition, which was designed to survey unusual structures under 10 to 15 feet of water along a southern shore of Laconia, at the end of the Greek Peloponnesian peninsula. The ruins had been discovered in 1968 but had only been crudely mapped and partially excavated. In 2009 archaeologist Jon Henderson arrived for a detailed look.
Engineers mounted two high-resolution cameras on a boxlike frame, which divers pushed in overlapping paths above the submerged structures below. Software combined the thousands of pictures with information about the speed and position of the rig, creating an exact photomosaic of the bottom—all without strings and measuring tapes.
The photomosaic created the first real representation of what was on the bottom: an entire town with streets among 15 buildings, rooms filled with jars, and tombs, all covering more than two acres. Dating of objects that were excavated put the oldest part of the city of Pavlopetri at about 4,000 years ago. It was the first underwater settlement to be digitally mapped and then modeled in 3-D. Henderson brought in Simon Clarke, a computer animation expert who had worked on the Harry Potter movies, for the final touch—he created a video animation that used the survey data to re-create a walking and gliding tour through the town as it had once been.
Carnage from Carthage
Another marine archaeology expedition that pioneered new technology to achieve its goals involved a series of trips to the Egadi Islands from 2005 to 2013.
For years the ancient city of Carthage had controlled vital trade routes between Africa and what is now Italy. Its big, hand-rowed boats had defeated Rome's vessels again and again, mainly by bludgeoning the opposing hulls with a great bronze ram fixed to the bow. In 241 B.C. the Romans built their own ramming fleet for a counterattack. Some 200 Roman warships bore down on several hundred Carthaginian warships and cargo ships. Historian Polybius said the confrontation was “the most severely contested war in history.” But he did not specify where it happened.
The Superintendent's Office of Underwater Archaeology in Sicily brought in Italian archaeologist Sebastiano Tusa and Jeffrey Royal of the RPM Nautical Foundation in Florida to search for the battlefield. Old documents hinted at a place just east of Levanzo Island, but the wreckage could have been strewn anywhere across 100 square miles of seafloor at depths down to 300 feet.
Tusa and Royal began their multiyear exploration with a research ship that sailed in a back-and-forth search pattern, fitted with an echo-sounding device on its hull. This “multibeam sonar” fired out 500 different pings at a time, at rates up to 40 pulses a second. By reflecting off the seafloor, the sound waves created a rough map of the huge area. Researchers analyzed echoes that seemed to indicate objects and could discern an array of wrecks, from modern airplanes to old ships. But the accuracy of any one location was relatively low.
After much analysis, the team returned with a more precise sonar imager, called a sector scanner. The scientists lowered it on a tripod to the bottom of a prospective site to get a closer and clearer sound image, producing ghostly shapes that were easier to identify. If the team deemed certain objects as important, it sent a remotely operated robotic submarine with cameras to locate it. Members onboard the ship saw what the robot was seeing through a video link. If they found an object, they would remotely manipulate mechanical arms on the robot, which had pincers at the ends, to try to pluck the relic from the muck and bring it to the surface—an unusual use of robots to fetch artifacts from ancient shipwrecks.
It was not until the very end of the search season in 2010, however, that Tusa and Royal came across what they were looking for: a wreck with a battering ram. Over the next three years they found eight more boats with rams, some Roman and some Carthaginian, and they retrieved all nine of the bronze batterers. The rams have markings that link them to the era of the naval battle. They also reveal a great deal about ocean warfare at the time: they were mounted on the bow of the oared ships, right at the water line, and they had three broad horizontal blades designed to cut through a boat's hull when they struck.
The capabilities of high-tech ocean archaeology are expanding quickly. Divers with rebreathers or Exosuits can sink to hundreds of feet and stay for hours. Robot vehicles piloted from ships or programmed to swim on their own can quickly cover not square yards but square miles, capturing digital imagery precise to fractions of an inch. In the future, explorers may operate entire underwater robotic stations that do not require expensive boats and crews. In his grandest dreams, Woods Hole's Foley imagines charting the bottom of the entire Mediterranean Sea and cataloguing thousands of wrecks that could provide keen insight into diverse cultures through the ages.
At a conference on marine archaeology in the fall of 2014, Royal also noted that the array of new technology makes exploration much cheaper and easier: scientists with a few thousand dollars could go to sites and return with 3-D images of striking objects. “More people can do this in more places,” he said. “And because there is very little money available, it's the way marine archaeology has to go.”
The entire history of seagoing humankind, frozen in time on the seafloor, has become accessible. As Foley noted to me on remote Antikythera before we departed, “98 percent of all the oceans depths are now in range for the first time.”