A scientific expedition to an ancient Mediterranean shipwreck reveals the luxurious lifestyle of wealthy Romans in the time of Caesar.
This year, marine archaeologists have been exploring the richest ancient Greek shipwreck of all time using 21st-century technology. The vessel, which sank in around 65 BC, was a 65-metre boat packed with luxury goods from the craftsmen of ancient Greece and the eastern Mediterranean, destined for the burgeoning Roman market. From the evidence of silver coins found on board, it probably began its journey in Pergamum or Ephesus in modern-day western Turkey, stopping off at the tax-free port and trading centre of Delos in Greece to pick up further goods. The ship sank off the coast of the tiny Greek island of Antikythera en route to a Roman port and the main market for its luxurious cargo.
Brendan Foley, a historian, archaeologist and diver from the USA’s Woods Hole Oceanographic Institute (WHOI), leads the expedition. “Every single dive delivers fabulous finds and reveals how the ‘one per cent’ lived in the time of Caesar,” he notes.
The ship carried art masterpieces of the age, destined for Roman villas: exquisite bronze and marble statues, glassware from Syria and Lebanon, ceramics, bronze couches and amphorae and most important of all, the unique Antikythera mechanism. This was a sophisticated astronomical calculator, dubbed the world’s first analogue computer and the only one of its kind ever discovered. Even after three waves of exploration, much of the cargo remains deep under the water, as yet untouched.
The wreck was first discovered in spring 1900 by sponge divers. A major recovery of its treasures was made later in the year with the help of the Greek Navy, by divers in bronze diving helmets who were supplied with air pumped from the surface. Jacques-Yves Cousteau visited the site in 1953 on his expedition ship Calypso and returned to lead a major excavation of the wreck in 1976 as part of a film project, using a small submersible. Yet it was not until 2014 that a major new expedition began working onsite, its first truly scientific excavation. The multi-year expedition is a collaboration between the Greek Ministry of Culture and WHOI.
“We’ve trained our marine archaeologists for five years to be ready to work this wreck,” Foley. “It’s deep, much of it lies at more than 50 metres and for us to be able to spend reasonable working time down there safely we’ve had to learn to use rebreather technology instead of scuba tanks and air.” The closed-circuit rebreathers chemically scrub the carbon dioxide from the exhaled breath and top up the inhaled breath with oxygen. To avoid the bends on ascent due to nitrogen accumulation in the body’s tissues, the necessary long decompression stops are made on gas mixes, culminating in the divers breathing pure oxygen near the surface.
This is technical diving, and planning is meticulous for safety reasons, with a diving supervisor on board the mother ship directing operations in constant communication with the divers below. A remotely operated vehicle (ROV) is piloted from the support vessel and is the surface team’s eye in the water, providing a real-time video feed and recording of the wreck operations. “The ROV allows us to make the best use of time and coordinate handovers between dive teams, and to synchronise activities from the surface,” says Foley.
Another robot, an autonomous underwater vehicle (AUV) called Sirius, was designed at the Field Robotic Centre at the University of Sydney specifically for this expedition. It was instrumental in creating a high-resolution 3D map of the entire site in 2014 and early 2015, using stereo cameras to collect overlapping images of the area. The data is processed using an algorithm known as simultaneous localisation and mapping (SLAM), to produce the map of the wreck. This multi-dimensional map of over 10,500m2 of seabed is allowing the archaeologists to perform a controlled excavation of the large debris field to the highest scientific standards. These maps are available to the divers on underwater iPads.
Side-scan and multibeam sonar maps of the entire island coastline also produced the first acoustic maps of the sea bed, which showed some tantalising objects the size of small cars 100 metres from the shipwreck and in 150-160 metres of water. Diving supervisor Phil Short said: “This is extremely exciting, as we learned that rock-like accretions pulled from the site in the 1900s were actually large sculptures including life-size marble horses. We plan to deploy the Exosuit, the latest manifestation of a one-atmosphere suit, to explore this area in 2016.”
The Exosuit is a one-of-a-kind diving system that maintains the pilot at sea-level pressure, allowing them to remain on the sea bed at depth for hours without incurring decompression penalties. Think of it as an articulated one-person submersible. It weighs half a tonne at the surface, but can be made neutrally buoyant in the water and has a set of gimballed thrusters.
“With a good operator inside, you could make that thing dance,” says Foley. “We hope to turn it into a valuable archaeological tool next season, and it’s the only bit of kit that we have at our disposal that can safely operate down to 300 metres.” The Exosuit will be used to locate, rig and lift the deep-water objects and also to excavate heavier items on the original wreck site.
Clearing the cover
Diving in 2014 was severely restricted by hurricane-force winds and bad sea conditions - the wreck lies just metres from the base of cliffs in an exposed anchorage. Only four diving days were possible, but divers were able to confirm that much of the ship’s cargo still lay under the sediment, sand and smashed pottery debris. Fortunately the weather was kinder this year and the 10-man dive team performed 61 dives in 10 days on the 55-metre site. Each archaeologist was accompanied by a professional technical diver who acted as their safety guardian while under the water. The pro divers also took care of the ‘heavy lifting’, such as dredging the site.
The archaeologists and divers carefully excavated a series of nine trenches this year using a water dredge and a submersible pump to remove coarse sand and smashed clay fragments that cover much of the area. From among these fragments the team recovered wooden remains from the hull of the ship, a section of bronze furniture - perhaps from a throne, part of a bone flute, a glass ‘chessman’ board-game element, bronze nails from the ship’s planks and parts of bronze, iron, glass and ceramic objects.
The team created 3D imagery of many artefacts in-situ in the seafloor trenches. Dr Theotokis Theodoulou, expedition co-leader and archaeologist at the Greek Ministry of Culture, says: “Apart from mapping the exact position of every find, the technology allows us to rebuild what we necessarily have to disturb during excavation. It also allows us to leave certain artefacts on the seabed in order to make a conservation plan for them ahead of lifting them to the surface.”
The team has 3D-modelled all of the major recovered artefacts, allowing scientists around the world to ‘examine’ extremely rare and precious objects and ultimately produce a virtual museum.
Theodolou says scientific analyses are now being conducted on these artefacts, including ancient DNA analysis of ceramic jars to identify the 2,000 year-old food, drinks, perfumes and medicines contained in them.
Underwater metal detectors revealed buried metallic targets all over the debris field, and a number of number of lead objects were salvaged. Archaeologists hope isotopic analysis of these will help to identify where the lead was mined, giving clues to what the vessel’s home port was