[Archport] Underwater robots can help study the world’s shipwrecks

[Alexandre Monteiro <no.arame@gmail.com>]

Marine archaeology: Davy Jones's lock-up

From The Economist, Dec 17th 2009 | WOODS HOLE


Underwater robots can help study the world’s shipwrecks, a trove of information about the past, more easily and cheaply


A SHIPWRECK is a catastrophe for those involved, but for historians and archaeologists of future generations it is an opportunity. Wrecks offer glimpses not only of the nautical technology of the past but also of its economy, trade, culture and, sometimes, its warfare. Until recently, though, most of the 3m ships estimated to be lying on the seabed have been out of reach. Underwater archaeology has mainly been the preserve of scuba divers. That has limited the endeavour to waters less than 50 metres deep, excluding 98% of the sea floor from inspection. Even allowing for the tendency of trading vessels to be coasters rather than ocean-going ships, that limits the number of wrecks available for discovery and examination.

Moreover, shallow-water shipwrecks are often damaged. Storms reach down to affect them. Seaweeds and corals, which need light to grow, colonise them. Freelance divers, seeking salvage rather than knowledge, despoil them. Archaeologists do sometimes team up with people who have access to miniature submarines (some manned, some unmanned) to explore deeper waters. But such expeditions are expensive—a million dollars a pop is not untypical—and archaeology is not a well-resourced profession. Often, these expeditions are privately financed, speculative ventures which amount to little more than treasure-hunting.

Modern robotics, however, is changing this. A new generation of cheap, free-swimming, automatic underwater vehicles (AUVs) is being developed. Past minisubs have needed a lot of backup and, if unmanned, have had to be guided by signals passing down tethers. Their mother-ships have thus had to be fitted out specially, which is one reason for the expense. An AUV, by contrast, can be dropped into the ocean and left to fend for itself. A wider range of vessels can thus support it.

One of the leading practitioners of the AUV approach to marine archaeology is Brendan Foley, of the Woods Hole Oceanographic Institution (WHOI), in Massachusetts. Having cut his teeth over the past few years on a vessel wrecked in the Aegean in the 4th century BC, he now proposes to make the process truly systematic and scientific. As he outlined at a meeting held in Alexandria, on December 15th, he hopes to survey a promising area of seabed off the coast of Egypt, with a view to locating and exploring all the wrecks therein.

Rendezvous with Rakham
The area in question is off Marsa Matruh, a port on Egypt’s northern coast that was a Bronze Age entrepot serving the Nile, Crete, the Aegean and the eastern Mediterranean. Using a new type of AUV called REMUS (remote environmental monitoring unit), which was developed at WHOI, and in collaboration with Emad Khalil, of Alexandria University, Dr Foley and his colleagues plan to scrutinise 15 square nautical miles of the abyss. This area will include regions near Zawiyet Umm el-Rakham (meaning “the rest-house of the mother of vultures”), a Bronze Age fortress-temple built by Ramesses II around 1280BC that would have been the focus of a lot of marine traffic. Any shipwrecks dating from that time would be the oldest seagoing vessels ever discovered.


Having an American robot swimming around the Egyptian coast is a disquieting thought for some of the country’s admirals, so one reason for the meeting was to explain to the navy and the coastguard exactly what is proposed. Provided Dr Foley and Dr Khalil get the go-ahead from the ministry of defence, they plan to unleash a REMUS next summer.

The probe in question is about two metres long, 19cm in diameter and weighs 37kg. It is equipped with cameras and sonar devices to record the sea floor’s topography, and sensors to record the water’s salinity, temperature and chemistry—including levels of chlorophyll and dissolved organic matter, which indicate how biologically active the part of the sea being examined is, and thus the likely state of preservation of any wrecks it contains. Those wrecks will, if all goes according to plan, be detected initially by sonar. Once a promising site is identified, the AUV will move in for a closer look and a detailed examination can begin.

Though they hope to find many more, Dr Foley and Dr Khalil already know of one wreck within their target area. This is a Roman vessel discovered last year by divers, near Bagoush, to the east of Marsa Matruh. This, and any other shipwrecks found, will be subject to an analysis similar to that which Dr Foley and his colleagues Katerina Dellaporta, of Greece’s ministry of culture, and Dimitris Sakellariou, of the Hellenic Centre for Marine Research in Anavyssos, applied to his previous target, a cargo vessel that had sunk off the island port of Chios, in water 70 metres deep. Dr Foley and his colleagues also discussed this find at the conference.

An earlier model of AUV called SeaBed was programmed to swim over the Chios wreck following a grid of squares with sides 2.5 metres long. Photographs and sonar images show that the wrecked vessel is 21 metres long, eight metres wide and 1.4 metres deep. SeaBed found about 350 amphoras from the ship’s cargo near the surface of the silt in which the vessel rests. These jars, which probably held olive oil and aromatic resins, are still contained within the wreck.

Half of the amphoras remain intact. Some are typical of the style of Chios, with an oblong shape, a high, straight neck and long handles. Others, of unknown origin, are globular, with short necks and short handles. The researchers spotted signs of additional layers of amphoras buried under the sediments, but are unable to work out their type or condition.

The fact that the amphoras are not scattered, and the lack of evidence of fire, or of trails of debris suggesting the crew were trying to lighten the ship’s load to stop it sinking, suggest that she went down suddenly and unexpectedly. Dr Foley therefore concludes she was sunk by one of the unpredictable, violent downdrafts of wind that the area is notorious for.

The Chios wreck—not discovered by Dr Foley’s team, but investigated by it—is, as it were, the flagship of this style of archaeology. Besides Greece, and now Egypt, Dr Foley is working with researchers and government officials in Cyprus, Algeria and Libya to extend the geographical reach of his approach throughout the Mediterranean. Arthur C. Clarke suggested in his novel “Rendezvous with Rama” that mankind would eventually drain the Mediterranean in order to study its archaeology. With AUVs around there will, fortunately, be no need.

http://www.economist.com/sciencetechnology/displayStory.cfm?story_id=15125181