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Sunk without trace
One hundred years ago, at 23:40 hours on 14 April, 1912, the Royal Mail Steamer Titanic collided with an iceberg in the Grand Banks region of the North Atlantic and sank within three hours; over 1500 souls perished. It remains one of the biggest peacetime marine disaster in history.
Seventy-three years later, on 1 September 1985, the Titanic was discovered in the Atlantic Ocean, 4km down, 100km off the forbidding Grand Banks of Newfoundland, during a joint French–American expedition. A prominent member of the team, archaeological oceanographer Robert Ballard describes seeing the wreck as one of the most moving moments of his life.
It was immediately clear to Ballard and his colleagues that the events of her foundering and the subsequent seven decades at the bottom of the Atlantic had not been kind to the Titanic. Ballard described the scene as ‘frozen rivers of rust covering the ship’s sides and spread out over the ocean floor’.
The Titanic rests in three parts, the two largest – the bow and the stern – are separated by a field of debris over 600m long. The debris is scattered over the South-East Newfoundland Ridge where the temperature is 1°C and the water pressure exceeds 6000psi. The stern, which snapped off the ship when the weight of water broke her keel, was badly damaged by multiple implosions of trapped air as it underwent its long fall to the sea bed.
However, what was not immediately obvious to Ballard and his team was that even after all those years the rate of the Titanic’s decay was accelerating. That only became clear after multiple dives spanning two decades.
‘Rivers of rust’
The ship is covered in a complex web of ‘rusticles’, so named because of their resemblance to icicles. Ballard’s ‘rivers of rust’, are the product of iron decay (see "Rusticles" below). They are delicate, the slightest touch – even from the wake of a submersible propeller – is enough to cause them to disintegrate into red powder.
Lori Johnston, a Canadian scientist who has dived on the Titanic a number of times to study the rusticles, estimates that about 300kg of steel is disappearing from the severed forward section of the Titanic every day. As the rusticles spread, they create pits and hollows in the steel, exposing more surface area. The effect is exponential, so that the time to complete decay is progressively shortening.
Johnston explains: ‘Rusticle-forming bacteria occur in many environments, but at the site of the Titanic they are one of the dominant organisms. The rate and extent of decay is unusual on Titanic because at that depth, there is little else that competes with these bacteria for the steel and nutrients in the environment, so the rusticles come out on top. We believe that this bacterial activity is increasing due to the continued availability of nutrients, steel surfaces and “seeding” from existing rusticles. Our research indicates that in 100 to 150 years Titanic will be a U-shaped shell of rusticles at the bottom of the North Atlantic.’
So in 200 years there will probably be nothing left of Titanic except a discoloured patch on the sea bed. It seems we have found Titanic only to be faced with the prospect of losing her again. Can anything be done to save her?
Lessons from Mary Rose
In contrast to Titanic, in Portsmouth, UK, the 467-year old Mary Rose has been restored to her former glory. Charles Barker – the director of Mary Rose Archaeological Services – comments: ‘It was possible to retrieve the 60% of what remained of Mary Rose intact. She was in only 11m of water. That obviously is not possible with Titanic at the water depth she is lying in. That alone makes the technical challenges much greater.’
Not only was Mary Rose recovered but it was still possible to do a conservation job on her because so much of the structure was wood. ‘The first few centimetres of the wood had experienced damage so we bulked the cellular structure with polyethylene glycol to support the wood when it is dried. Obviously, with Titanic, wood is a much smaller component of the overall structure.’
Unlike the Mary Rose, where the cellular damage to the wood was caused by anaerobic bacteria, the damage being done to Titanic is mediated by aerobic bacteria. Ironically, metal structures from the interior of Titanic are often better preserved than those on the outside because inside the vessel the oxygen concentration is lower. This is borne out by the different colours of rusticle inside the ship, compared with those on the outside.
Barker points out that severe corrosion had also been found on some artefacts recovered from Mary Rose before they were disturbed during excavation. ‘The guns were iron and were massively corroded for the most part. The only rare exceptions were when one iron artefact was lying in proximity to another so as to become a sacrificial anode. In this case, one tended to suffer disproportionately at the expense of the other. We found a gun and sword that were in much better condition than other artefacts on the Mary Rose for this reason.’
The challenge for iron and steel artefacts recovered from Titanic and brought to land is that in ambient conditions the salt that has been absorbed in the iron through microscopic flaws expands and contracts as the humidity fluctuates. This causes the iron to fracture and delaminate. So as soon as diving expeditions have recovered metal from Titanic it must be immersed in de-ionised water and then subjected to electrolysis to stabilise it.
In fact RMS Titanic, a sub-division of Premier Exhibitions, which owns the salvage rights to the Titanic, is already making good progress salvaging and preserving artefacts from the wreck site (see "Preserving Titanic's artefacts" below). But controversy surrounds its work. Not everyone is happy that the salvage rights went to a single US corporation, and some people, including Ballard, believe the wreck should be left alone.
After a long legal battle that lasted 20 years – during which RMS Titanic nearly went bankrupt – the District Court of the Eastern District of Virginia, US, ruled that although Premier Exhibitions owns the wreck and associated artefacts, it is not free to do with them as it wants. For example, it must monitor the wreck site and any dives made onto it. In addition, there is a long list of restrictions concerning the preservation and disposition of the thousands of artefacts it now owns. For instance, they cannot be sold piecemeal and if the collection is ever sold en masse the buyer must agree to maintain and preserve it.
So the legal situation does at least have the advantage that the irreplaceable artefacts of the Titanic are not spread around the globe. The priceless collection of artefacts will stay together for posterity.
Ballard has been vocal in his criticism of artefact collection from the wreck. He maintains that it is a grave site and that it should be treated with respect. He told National Geographic: ‘Come and see the Titanic ... But don’t tear it up, don’t land on it, don’t run into it.’
It is sadly true that the Titanic has not been allowed to rest in peace since her re-discovery. After the initial dives by Ballard and his French team-mates, literally dozens of visits to the wreck site have been made, not least by acclaimed film director James Cameron who used footage of the wreck for his 1997 academy award winning film Titanic, which is released in 3D this month. But ‘sightseeing’ on what is effectively a mass grave has been criticised, not least by Ballard, who has said: ‘I urged others to treat the Titanic’s remains with dignity, like that shown [to] the battleship Arizona in Pearl Harbor. Instead they turned her into a freak show at the county fair.’
It is hard to disagree when a least one couple has been married in a submersible resting on the poop deck of the liner. But RMS Titanic has said that after the centenary of her sinking this month it will not allow any further visits to the site of the wreck.
This is just as well. Recent reports say that the wake of a submersible propeller is now sufficient to initiate ripples in the steel plates of the stricken liner’s decks. Perhaps the centenary is finally the time to let Titanic – and her long-dead passengers and crew – slide quietly into the grave of history.
Rusticles – the ‘rivers of rust’
The deterioration of the Titanic – quite apart from the damage done by the events of 14 April 1912 – is largely biochemical in nature. Repeat visits since Titanic’s discovery have revealed that the rusticles are growing larger and denser while the ship continues to deteriorate.
Microscopic investigations show that the rusticles are made up of iron oxides and hydroxides together with complex bioconcretious structures involving many communities of bacteria and fungi, which apparently co-exist in some form of symbiosis and feed off the rusting metal. The rusticles grow in a fantastic variety of shapes and colours, which add to the desolate air of the decaying wreck.
The variation in colour, from a yellow to purple, is due to the highly oxidised ferric iron content. Rusticles with a grey or black hue are found inside the ship where the oxygen content of the seawater is lower than outside.
There is considerable variation in the rusticles’ composition. The iron content ranges from 24 to 36%, in the form of complex ferric oxides and hydroxides. Near its base, each rusticle structure is dominated by heavily mineralised growth in which goethite, iron oxyhydroxide, is dominant. An iron oxide sulfate complex,
(Fe2+3.6 Fe3+0.9(O2-,OH-,SO42-)9), known as ‘green rust’ has also been found. Electron diffraction reveals the presence of other elements in the rusticles, in the following order of prevalence: Fe > Na > S > Cl > Mg > Si > P > Mn.
Preserving Titanic’s artefacts
The Titanic’s conservators follow strict processes, not only to remove rust and salt deposits from each recovered artefact but also to stop the object further reacting with the air.
Once removed from the water in the recovery vessel, the artefact is cleaned with a soft brush and transported to the lab in a foam-lined tube of water. At the lab, the artefact is washed repeatedly in de-ionised water to remove any contaminating surface salts. Different artefacts are then treated differently:
- Metal objects are placed in a desalination bath to initiate electrolysis. A metal cage, connected to an electrical current, covers the object – which removes the negative ions and salt from the artefact.
- Conservationists have recently begun to use electrolysis to remove salts from paper, leather and wood artefacts. These materials are first treated with chemical agents and fungicides to remove rust and fungus.
- Organic artefacts, such as wood and leather, as with the Mary Rose’s timbers, are injected with polyethylene glycol to stabilise the structure and then freeze dried.
- Artefacts made of paper are first freeze-dried to remove all the water, then treated to protect against mould and subsequently conserved for exhibition.
All recovered artefacts are maintained at controlled levels of temperature, humidity and sunlight.
Richard Corfield is a science writer based in Oxford, UK.