With the discovery of the wreck in 1985, one of the prominent features was the presence of what appeared to be formations of rust structures on the hull termed "rusticles" by Dr. Robert Ballard. The formations were rust colored and hung down like icicles. The common relationship between rust and the deterioration of iron and steel structures led to the natural linkages between these rusticles and the rate of physical deterioration of the ship. With ten years of observation, there has been an ongoing disintegration of the bow wreck featuring the collapse of the top deck over the gymnasium and loss of the canopies to the crow's nest. Much of the bow of the Titanic is covered with these rusticular growths and there are particularly intense clusters growing along the promenade deck, over the stem, and over the port side plates which show signs of buckling.
Before 1996, expeditions to the wreck site did not study the rusticles and their effects on the deterioration of the plates and their rate of growth. The wreck site is clearly oxidizing with many marine organisms (oxygen respiring) living on or around the site.
The color of the rusticles would suggest oxidized forms of iron (i.e. ferric oxides and hydroxides along with some carbonates) may have caused the rust color. Recent work by Professors Leighly and Long at the University of Missouri-Rolla, using Mössbauer spectrometry has shown that the rusticles contain goethite (Fe[OOH]). This is an authosiderite which appears to be very pure, fine grained, and contains few defects which is not surprising considering the low temperatures at which this goethite formed and its possible slow rate of formation. Clearly, since the rusticles contained iron, there is the probability that a very significant fraction would have been extracted from the steel plates of this once great liner to now reside in the growing structures. Questions are naturally raised as to the nature of the events that led to the iron being extracted from the hull plates to the rusticles. Is this primarily a chemical, physical or biological event? One of the dives of the submersible Nautile in August 1996 focused on this question. Various rusticles were collected and a survey made of the extent of these infestations.
Some basic information was gleaned from the samples brought back to the
surface and from subsequent growth from fragments of hull plates and
artifacts recovered from the debris field. Analysis was made at the University of
Regina, while Dr. Henrietta Mann accomplished electron micrography and
microbial identification at St. Mary's University in Nova Scotia, Canada.
Based on these studies, it was determined that:
The microscopic examination revealed that the rusticles are porous with complex fibrous (or thread-like) structures incorporating various iron dense commonly plate-like structures. The whole rusticle is bounded by a surface rich in iron and slimes with various crystallized structures. Lacing through this porous mass are water channels and reservoirs which interconnect with each other and to surface ducts. Major threads interlace these porous structures and some span across the water passageways to give additional mechanical support to the rusticles.
Mr. Scott Miller of the Department of Metallurgical Engineering at the University of Missouri-Rolla examined samples of rusticles using a scanning electron microscope. He performed elemental analysis as well as semi- quantitative analysis. The result is given in Figure 10. As expected, Iron (Fe) is the dominant element present, followed by Sulfur. The sulfur is present as the sulfate ion, SO4--, could be from the sulfur in the steel or more likely from the sea water which has 884 part per million content of sulfur  The silicon will be shown to be mechanically entrained as silica, SiO2, from the ever- present sand at the ocean bottom.
Dr. Mark Shumsky of the Materials Research Center at the University of Missouri-Rolla performed x-ray diffraction determinations to identify the compounds in a sample taken from a rusticle and from a massive piece of of the corrosion product taken from a piece of steel. The same three compounds were found in these two samples, but in differing concentrations in each sample; silica, which is sand and discussed in the previous paragraph, goethite (FeO(OH)), and iron oxide sulfate, also known as green rust, (Fe+23.6Fe+30.9(O--, OH-, SO4--)9). It is a mixture of ferrous iron, Fe+2, and ferric iron, Fe+3, plus a mixture of anions (O--, OH-, SO4--). In Figure 11, the diffraction pattern is given.
There remains much to be learned from these rusticles in terms of their basic biology and chemistry, but it is equally important to evaluate the likely physical compromise of the existing structures forming the Titanic. Since the rusticles contain high concentrations of iron which has almost certainly arisen from the bio-extraction of iron from the steel, it is likely that the growth of rusticles will exacerbate the weakening of the steel plates and eventual collapse of the hulk. The rusticles appear to be bio-concretions, that is a hardening porous concreted mass which has formed, at least in part, through a biologically induced colonizing by various microbial growths. From a visual inspection of the bow section, it is estimated that 65% of the 0.75-inch plate , 25% of the 0.375-inch bulkheads, and 10% of the machinery may now be coated with attached rusticles to a mean depth of 20 mm (0.8 inches). Preliminary calculations indicate that the mass of the rusticles may weigh as much as 650 tons which could include as much as 175 tons of iron. These highly porous and expansive structures on the bow wreck have an internal minimum surface area of almost 6,280 square miles.
Three principal forms of rusticle growth were detected on the bow wreck of the Titanic. The large structures with extensions hanging down the sides of the hull could be clearly observed to be deflecting the direction of water flow at that site. For example, the starboard hull near the stem is buckled inward. This has caused a change in the flow pattern which resulted in the hanging section of the rusticle to bend horizontally pointing downstream to the flow. Most of the appendages hung vertically in the relatively slow water current of 1 to 1.5 knots from stem to stern. The second form of rusticle was a tightly concentric clustered type which remained tightly attached to the hull and showed little sign of growing quickly. The buckled port hull plates close to the stem were heavily festooned with this form of growth. This suggests that they may have infested the damaged steel plates. The third type of rusticle has a confluent enveloping form of growth which is able to penetrate into gaps and cracks in the steel plating as well as envelope surfaces with a continuous coating of rusticles. These forms often contain embedded coal, glass fragments, clays, and stones which have landed on the Titanic with the debris which has fallen on the ship since the sea bed impact. The microbiology of the rusticle reveals that there are bacteria and fungi present in the growth, which tends to be clustered consortial forms of microbial activity sometimes dominated by Iron-Related Bacteria (IRB), Sulfate- Reducing Bacteria (SRB), and fungi. The more centralized passages within the rusticles are often darker brown or black. Tests were conducted to determine the aggressiveness of the growths and the different types of bacteria present. Of particular interest were the SRB groups which would produce a positive reaction and concurrently release colloidal floc to the water. This resembled the "sea snow" which is prevalent around the Titanic. Parallel examination of a tuberculous formation on a recovered copper telegraph revealed the presence of sulfur-oxidizing bacteria, Thiobacillus, but no SRB, IRB, or fungi.
At the time of the microbiological investigation dive to the wreck, there was a considerable amount of "sea snow". These are flocculent colloidal floating particles which gradually descend like a gentle snowfall. The "sea snow" is white in color and could be seen collecting on any lateral catchment site, such as the shoulders of the rusticles. Although the rusticles are generally shades of orange through brown and purple, the coating of "sea snow" gives them a grey appearance.
The robotic arm on the Nautile was used to test the strength of one of these rusticles that was 6 feet long and 2-3 inches in width. A gentle touch of the midpoint of the rusticle caused a burst of red dust, outward for some 30 centimeters, from a fixed site (presumably a duct). Clearly the physical pressure of the robotic arm caused some hydraulic pressures within the rusticle structure which were relieved by the venting of liquid through a duct on the opposite side to the point of impact. The emergence of this red dust prompted a second try with a gentle touch. This time the rusticle's arm disintegrated in a diffuse yellow cloud that enveloped the Nautile in a cloud for several seconds. At the same instant, the foot of the rusticle detached and floated down in a circular manner into a collection tray on the Nautile. It was recovered for further examination and analysis. This exercise, however, revealed that the rusticles are delicate structures that have some ability to flex and vent red dust, but they will collapse when moderate physical force is applied.
Two types of in situ culture platforms were placed on the Bridge Deck of the Titanic to determine the presence of bacterial activity. The first type used strips of unexposed but developed Fujichrome 100 A.S.A. film folded in a concertina fashion within a cellulose textile. This was carefully laid flat onto the rusticles so that the bacteria would travel upward through the textile to the film's emulsion. Since the emulsion is black with the primary colors and composed of gelatin, the bacteria were able to degrade this gelatin protein causing the emulsion to erode and revealing some of the colors. The bacteria which etched the gelatin are proteolytic. The textiles on one of the culture platforms that was in situ for 20 days became coated with the pigments being released from the etching film emulsion showing that proteolysis had occurred. When this platform was recovered and examined at 40X magnification, complex patterns created by the bacteria mining the gelatin were observed.
The second type of culture platform utilized a modified BARTTM (Iron Related Bacteria, IRB and Total Aerobic Bacteria, TAB) which had a perforated conduit which connected the underside of the bio-detector to 10 mm (0.4") above the underlying rusticle. Here, the bacteria penetrated the test vial and essentially removed the crystallized selective medium. The IRB test was in place 20 days before recovery and it appeared that the medium from this test vial had been taken up by the rusticle underneath. These experiments revealed that the rusticles include proteolytic bacteria as well as IRB and aerobic bacteria. Further identification of these bacteria is still on going. Dissection of a rusticle reveals a somewhat randomized relationship between the various porous, plate-like, and water-bearing structures with threads very commonly found interconnecting these various components. The microbiology of the rusticle reveals that there are both bacteria and fungi present in this growth, but there tends to be clustered consortia of microbial activity sometimes dominated by IRB, Sulfate- Reducing Bacteria (SRB) and the fungi. The more central passageways through the rusticle are often a dark brown or black, suggesting more reductive conditions which could be more suitable for the SRB rather than the oxidative conditions that would support the IRB and fungi. Various consortia were detected using the Biological Activity Reaction Tests (BARTTM). All of the above microbial groups that were recovered can be described as being aggressive from the various tests of the rusticles examined by this technique.
The impact of the rusticles on the Titanic remains a critical issue. If they are rich in iron extracted from the ship, there is an inevitable consequence that the ship structure will weaken and eventually collapse. A number of considerations can be drawn concerning the rusticles based upon the coverage of the exposed hull plates with rusticles. From visual inspections of the bow of the Titanic, it is estimated that 65% of the side shell which ranges between 0.75 inches to 1.0 inches, 25% of the bulkhead plates which vary in thickness from 0.375 to 0.625 inches, and 10% of the machinery were coated with attached rusticles to a mean depth of 0.8 inches. A preliminary estimate indicates the mass of rusticles at no less than 650 tons which could be interpreted to include 178 tons of iron (assuming a 27% iron content). Since there is no adequate method to complete a more accurate assessment of the rusticle infestation within the hull or the loss of iron from the wreck itself, it remains uncertain how much iron has been extracted from the Titanic steel thus far.
At the University of Regina in Saskatchewan, Canada, Dr. Roy Cullimore has just begun the analyses of the rusticles. These studies will require a data bank to project with confidence the rate of bio-deterioration of the Titanic to the point where the two hulls would no longer exist as definable entity.