December 2, 2013
Lead Ingots From Shipwrecks Being Used To Hunt For Dark Matter
Gerard LeBlond for www.redorbit.com - Your Universe Online
A Roman vessel carrying ingots of lead, which was removed from the Sierra of Cartagena, sank more than two thousand years ago off the coast of Sardinia.
Now, more than a hundred of these lead bricks have been used to build the ‘Cryogenic Underground Observatory for Rare Events’ (CUORE), an advanced detector of almost weightless subatomic particles (neutrinos) and is located at the Gran Sasso National Laboratory in Italy.
Another vessel carrying lead bricks sank off the coast of France in the eighteenth century. Treasure hunters have recovered these bricks and were able to sell them to Cryogenic Dark Matter Search (CDMS), despite opposition from French authorities. The CDMS is a dark matter detector located in a mine in Minnesota.
Scientists from the CDMS dark matter detection project and from the CUORE neutrino observatory have begun to use these recovered bricks, as their properties are ideal for particle physics experiments. However, this has sparked a controversy with archaeologists.
Scientists say the material is excellent because of its unique properties for use on the research of neutrinos and dark matter. Archaeologists state they are concerned about the destruction of underwater cultural heritage.
Elena Perez-Alvaro, from the University of Birmingham, explains, “Roman lead is essential for conducting these experiments because it offers purity and such low levels of radioactivity - all the more so the longer it has spent underwater - which current methods for producing this metal cannot reach.”
Fernando González Zalba, a physicist from the University of Cambridge, adds, “Lead extracted today is naturally contaminated with the isotope Pb-210, which prevents it from being used as shielding for particle detectors.”
Perez-Alvaro also stated, “Underwater archaeologists see destruction of heritage as a loss of our past, our history, whilst physicists support basic research to look for answers we do not yet have. Although this has led to situations in which, for example, private companies like Odyssey trade lead recovered from sunken ships.”
However, Odyssey has been previously forced to return treasures to Spain that it had taken from the sunken frigate Nuestra Señora de las Mercedes.
Both physicists and underwater archaeologists are supporting the idea of dialogue between them, as well as legislation to regulate this type of activity in the future. Scientists stress that such recoveries should include knowledge for both fields and not just for commercial purposes. As well, regulations need to be enforced pertaining to both archaeologists and scientists.
The inscriptions from the lead bricks used for CUORE were cut out and preserved, but some archaeologists suggest that should other valuable metals such as anchor stocks be found, assessments should be made before they are sacrificed in the name of science.
Perez-Alvaro says there are many theories as to how the Romans used these bricks, “but they were generally used as water-resistant material for pipes, water tanks or roofs, but also in the manufacture of arms and ammunition.”
The recovery of lead bricks from the Bou Ferrer, a large Roman ship that sank near the port of La Vila Joiosa in the Mediterranean, was a particularly special case. The bricks recovered had engravings on them, and specialists determined they were the property of the Emperor of Rome -- most likely Caligula, Claudius or Nero.