Called Exosuit, the suit has a rigid metal humanoid form with Iron Man-like thrusters that enable divers to operate safely down to depths of 300 metres (see photo).
Though designed for diving in the bowels of New York City’s water treatment plants, earlier this month it underwent its first trials in seawater at the Woods Hole Oceanographic Institution (WHOI) in Massachusetts. The tests are readying the suit for a daring attempt to excavate an ancient Roman shipwreck off the Greek island of Antikythera in the Aegean Sea. A century ago, divers pulled the world’s oldest computer – the Antikythera mechanism – from the wreck. They are hoping that they will find a second device when they go down in September.
Marine archaeologists normally wear scuba gear to explore underwater sites in person, but the time that divers can spend at depth is limited by the dangers of decompression sickness, or the bends. For deep wrecks, researchers rely on remotely operated vehicles (ROVs) carrying cameras and sonar to scan an area, or large and expensive craft like the Alvin submarine that explored the wreck of the Titanic in 1986.
The $1.5 million Exosuit falls somewhere in between. “It’s basically a wearable submarine,” says Phil Short, a diving specialist on the planned mission to Antikythera. “The pressure inside is no different from being in a submarine or in fresh air. We can go straight to the bottom, spend 5 hours there and come straight back to the surface with no decompression.”
The suit is made from an aluminium alloy, with articulated joints that permit divers to move their arms and legs freely. An umbilical cable from a ship supplies it with power for horizontal and vertical thrusters, and a rebreather that scrubs toxic carbon dioxide from exhaled air, giving 50 hours of life support. The cable also carries voice, video and data links. In the event of an emergency, a battery can power everything but the thrusters, including a back-up communication system.
Foot pedals inside the Exosuit control the four thrusters to manoeuvre it through the water. And if a diver is busy with a complex task underwater, an operator topside can monitor the Exosuit’s video feed and fire the thrusters to keep it in position – or even take over completely and bring the suit back to the ship.
The Exosuit is needed both because of the depth of the Antikythera wreck – it reaches 120 metres – and the delicacy of any artefacts that might lie within. When Greek sponge fishermen found the shipwreck in October 1900, the pressure was such that they had only 5 minutes on the seabed before having to ascend. It was risky: several divers were paralysed and one died from decompression sickness.
By the time underwater explorer Jacques Cousteau led an expedition to the ship in 1976, the amount of time that could be spent at the bottom had been extended to just 10 minutes. To maximise their efficiency, Cousteau’s divers used a vacuum system to suck up a small area of the wreck, but this risked damaging or destroying priceless fragile objects.
The new expedition won’t face such time constraints. “With the Exosuit, our bottom time becomes virtually unlimited,” says Brendan Foley, co-director of field operations at WHOI’s Deep Submergence Laboratory. “Now we can have an archaeologist in the suit for hours, and we’ll only have to come up to answer the call of nature.”
Despite the limitations of earlier expeditions, the treasures that were recovered at Antikythera represent some of the finest ancient Greek and Roman artefacts in existence. They tell the story of a Roman ship that foundered on the rocky shores of the island around 60 BC. The ship was laden with luxury goods, including bronze and marble statues, precious jewellery, a hoard of coins, glassware, ceramic jars – and fragments of a peculiar geared device whose importance was at first overlooked. Only in the 1950s did scholars figure out that the rusty metal pieces could be assembled into a sophisticated analogue computer for predicting astronomical events. They called it the Antikythera mechanism.
Ironically, 2000 years spent in corrosive saltwater may have been the best way to preserve these riches. Most precious objects from antiquity have been broken up or melted down over the millennia. The National Archaeological Museum in Athens has only 10 major bronze statues from Ancient Greece – and nine of them came from shipwrecks.
Foley believes that the Antikythera shipwreck still holds many secrets. A preliminary survey last year showed artefacts scattered over an area 50 metres by 10 metres, and even revealed a previously unknown shipwreck alongside the first one.
“We have feet, arms and the crest of a warrior’s helmet from statues recovered in 1900 – maybe we’ll get lucky and find the rest of them,” says Foley. “But for me, the mechanism is what sets this wreck apart. It’s the questions it opens up about the history of science and technology that fire my imagination.”
Image: Mark Harris