Underwater robots can help study the world’s shipwrecks, a trove of information about the past, more easily and cheaply
Jack Linthicum
divers. Expensive and cumbersome, the robot automatic underwater
vehicle, 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.
If the site is demonstrated to have promise then then the more precise
investigation can be performed by divers where possible and
sophisticated robots where the divers cannot reach.
Davy Jones's lock-up
Dec 17th 2009 | WOODS HOLE
From The Economist print edition
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.
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