Rusticles

The Titanic is being eaten by “rusticles”

When Robert Ballard’s team of explorers discovered the Titanic on the Atlantic floor in 1985, no one was surprised that it was covered with rust. But 10 years later, when the Titanic’s gymnasium roof was discovered collapsed, researchers got a lot more curious about the corrosive material on the ship.

Was something other than rust at work?

Rusticles
Rusticles
Courtesy SMM

A closer inspection showed the “rust” was actually red/brown stalactites, which were nicknamed “rusticles.” The rusticle structures contain both rust and complex communities of bacteria that live off the rusting metal. (The same iron related bacteria plug up pipes, screens, and pumps in water wells.)

How do we know that? Look at this PDF. In expeditions in 1996 and 1998, microbiologist Roy Cullimore was brought on board to analyze the rusticles and see if the bacteria were playing a role in the ship’s destruction. He used a simple experiment to do this.

Cullimore took unexposed slide film and developed it. He put the black slides into bags made of Aida cloth, which has small holes in it that allow bacteria to pass through. If bacteria were present on the ship, they would eat the emulsion side of the slide film inside the bags, releasing colors in the emulsion and staining the Aida cloth. Under a microscope, the colors would reveal complex patterns of bacterial activity.

That’s exactly what Cullimore found. He took samples of rusticles to his lab for further study, which has shown that there are a variety of microbes present in them. They’re contributing to Titanic’s deterioration, and will eventually help cause its collapse. Scientific estimates about how long Titanic has left range from 15 to 450 years, but at some point in the future the mighty ship will be nothing more than an iron deposit on the ocean floor.

Try it yourself:
You can do an experiment at home similar to Dr. Cullimore’s.

You’ll need:

  • A roll of slide film, developed.
  • Aida cloth and sewing materials to create little bags.
  • A container filled with potting soil or access to soil, as well as a spray bottle for misting. (The container should be large enough to completely bury half your slides.)
  • Access to an aquarium containing fish, and a separate container for water removed from the fish tank. (The container should be large enough to completely submerge half your slides.)
  • A microscope or slide projector (optional).

Now follow these steps.

  • Purchase a roll of slide film and get it developed without taking any pictures. The resulting slides will be black.
  • Create little bags—each large enough to hold one slide—out of Aida cloth. The holes in the Aida cloth allow microbes to reach the slide film while still protecting it from debris and damage.
  • Bury some of the bagged slides just under the surface of soil. Use your mister to keep the surface damp, but not soaked. Suspend other bags in aquarium water. (Note: The silver salts in the slide film might harm fish. Instead of using an actual aquarium, move some aquarium water and bottom gravel to a new container.)
  • Remove and examine one slide per day from each container. If bacteria are present, you’ll see evidence of their growth as branching tunnels etched onto the slides. Using a microscope or a slide projector, you can likely see deeper tunnels. (Note: Bacterial growth typically slows during colder weather. If you try this experiment when daytime highs are below sixty degrees, it may take a few days before you can see any results.)