Sunday, August 12, 2007

 

Mary Rose fights the acid reign of bacteria

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Telegraph
By Richard Gray
August 12, 2007


One of Britain's greatest archaeological treasures, the Mary Rose, is facing the biggest threat to its survival since it was raised from the seabed 25 years ago.

In contrast to the towering French warships it faced as Henry VIII's flagship, it is fighting a much smaller, though no less daunting, enemy. Scientists have discovered that bacteria growing on the timbers of the Tudor warship are producing a corrosive acid that could cause the hull to disintegrate.

They believe that the bacteria, together with a chemical reaction involving iron from rusted bolts and nails, is converting nearly two tons of sulphur in the waterlogged wood into sulphuric acid.

They fear that the remains of the 150ft-long ship will crumble to dust as the acid eats away the hard material in the wood as it is dried out.

"We have neutralised a lot of acid but there is the potential for more to be produced," said Mark Jones, the chief scientist at the Mary Rose Trust.

"A lot of the sulphur compounds we are seeing in the wood appear to be bacterial in origin.

"There also seems to be a role for the iron from the fittings and bolts, so we are trying to get rid of the iron particles that have worked their way into the wood."

The Mary Rose sank in 45ft of water off the south coast of England during a battle with the French invasion fleet in 1545, drowning about 500 sailors.

Half of the hull rotted away during the centuries spent on the seabed, but the rest was preserved in layers of silt, which protected the wreck in an oxygen-free environment and prevented marine worms from destroying the timber.

The Mary Rose was salvaged in October 1982 from the Solent, near the Isle of Wight, and is being preserved in Portsmouth.

Ironically, researchers believe that the oxygen-free years set the stage for the current problem, because they favoured rare bacteria - extremophiles, capable of living without oxygen - which gradually generated sulphur in the wood.

Once the hull had been raised and exposed to the air, other bacteria that live off the sulphur and convert it to acid colonised the timbers.

The Mary Rose Trust has launched a bid to secure £20 million of funding from the Heritage Lottery Fund to help build a new museum around the wreck and continue the preservation process.


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