"It is remarkable that this technique at the ESRF allows us not only to image and locate these nanoparticles inMary Rosewood, but also to evaluate their structure. This is the first time zinc sulfide nanostructures -- the bacterial byproducts -- have been observed inMary Rosewood," says senior author Serena Cussen, head of the Department of Materials Science and Engineering at the University of Sheffield, UK.

As Eleanor Schofield (@E_Schofield), co-author on this work and deputy chief executive at theMary RoseTrust explains, "Centuries spent under the seabed saw the uptake of harmful iron and sulfur species by theMary Rosehull, which were produced through degradation of metal fixtures and artifacts and anaerobic sulfur-reducing bacteria, respectively."

To compensate for degradation of the wood and loss of material, conservators impregnated theMary Rosewith a polymer called poly-ethylene glycol (PEG). This prevents shrinkage upon drying and gives the ship mechanical stability so it can be displayed for the public. In the final stage of active conservation, theMary Rosewas dried, and this exposure to oxygen has led to the formation of acidic species which can create even more damage to the wood.

"Up to now, it has not been possible to obtain quantitative structural information about the nature of these potentially harmful species residing withinMary Rosewood," says Cussen. "This is because it is really challenging to assess the range of materials present within archaeological samples, which can include amorphous, nanostructured, and polycrystalline materials."

When characterizing precious cultural artifacts like theMary Rose, it is important to use a method that does not damage the material. Cussen and her colleagues used a technique at the ESRF called X-ray computed tomography to provide detailed structural information about the wide range of materials present in theMary Rosehull without destroying the sample.

The researchers mapped out where compounds were lodged in the material by combining X-ray computed tomography with pair distribution function analysis (ctPDF). Using these two methods together allows them to determine the distance between the PEG and the nanoparticle products and therefore assess where potential threats lie within the wood.

"What our results have done is alert conservators to these previously unknown deposits and expand the study of degradation-inducing materials. Knowing the structure of these potentially harmful species also allows us to design targeted treatments for their future removal," says Cussen. In collaboration with theMary RoseTrust, her team is also developing a series of magnetic nanoparticle-based treatments to target and remove these harmful deposits within artifacts.