Slipping beneath the waves on April 15, 1912, the R.M.S. Titanic famously disappeared from view until 1985, when it was rediscovered on the bottom of the North Atlantic (pictures of Titanic's rediscovery).

Now, scientists say, the legendary liner—beset by metal-eating life-forms, powerful currents, and possibly even human negligence—could be vanishing for good.

Titanic is falling apart.

Already explorers have documented caved-in roofs, weakening decks, a stern perhaps on the edge of collapse, and the disappearance of Titanic's crow's nest—from which lookout Frederick Fleet spotted history's most infamous iceberg. (Watch an animation of Titanic's iceberg collision, breakup, and sinking.)

"Everyone has their own opinion" as to how long Titanic will remain more or less intact, said research specialist Bill Lange of Woods Hole Oceanographic Institution in Massachusetts.

"Some people think the bow will collapse in a year or two," Lange said. "But others say it's going to be there for hundreds of years."

With Lange as optical-survey leader, a new expedition sets sail Sunday from St. John's, Newfoundland (map)—roughly 350 miles (560 kilometers) from the ship's 2.4-mile-deep (3.8-kilometer-deep) resting place (Titanic wreck-site map).

The goal: to virtually preserve Titanic in its current state and to finally determine just how far gone the shipwreck is, and how long it might last.

"We're trying to bring the actual hard data to the people who can make those determinations," Lange said.

Titanic Tech

The 20-day Expedition Titanic will use remotely operated submersibles to complete an unprecedented archaeological analysis of the two- by three-mile (three- by five-kilometer) debris field, including Titanic's two halves. The ship's bow and stern separated before sinking and now lie a third of a mile (half a kilometer) apart.

Thousands of high-resolution photos and video will be combined with acoustic and sonar mapping data to form a 3-D replica of the site, allowing scientists and armchair explorers to probe it in detail. (Explore a 2004 photomosaic of the Titanic wreck.)

Some photos will reveal never before seen parts of Titanic, organizers say. Other images, when compared to evidence from earlier years, will help experts gauge the rate of the wreck's deterioration.

Expedition Titanic will gather hard data too, for example by measuring the thickness of the ship's hull and by hauling up and examining experimental steel platforms placed at the site.

In addition, scientists will take readings of the surrounding water to uncover its ability to support marine life—a prime cause of Titanic's deterioration.

Titanic Already Seen Crumbling

P.H. Nargeolet, co-leader of Expedition Titanic, made more than 30 submersible dives to the Titanic site in the 1980s and '90s—and saw it decline all the while.

Between 1987 and 1993, Nargeolet observed the gymnasium roof corroding and collapsing as well as the upper promenade deck deteriorating. On an early '90s dive he saw that the crow's nest—previously seen still attached to the forward mast—had disappeared altogether, apparently damaged to the point where it snapped off and fell to an as yet unidentified location (interactive Titanic wreck diagram).

"In some places I saw a lot of difference, and in others almost nothing visible has happened," said Nargeolet, director of underwater research for RMS Titanic, Inc., a for-profit corporation that has retrieved Titanic artifacts for traveling exhibitions.

"For example, the stern section was the most destroyed part of the ship when it sank, and now most of the stern section is collapsed," he said. "The bow is pretty narrow and the strongest part of the ship, and it's still in relatively good condition."

What's Eating Titanic?

On the ocean floor, Titanic is at the mercy of several processes.

For one thing, the once 883-foot-long (270-meter-long) ship is a sprawling feast for marine organisms. Mollusks have consumed much of Titanic's wood—leaving the metal hull to microscopic bacteria and fungi.

As the microbes eat away at Titanic, they form self-contained, icicle-like biological communities called rusticles. By 1996 there were some 650 tons (dry weight) of rusticles on the outside of Titanic's bow section alone (picture), according to estimates by microbiologist Roy Cullimore, a veteran Titanic explorer. Since then rusticles have continued to grow both inside and outside the wreck.

Rusticles may also infest the interior of the forward mast, which as a result may completely collapse in the next year or two, according to Cullimore, founder of Regina, Canada-based Droycon Bioconcepts, Inc., a biotechnology company.

The upper promenade deck is also slowly crumbling, he said, and may implode within the next two decades at the current pace.

To build Titanic, Cullimore said, humans mined "iron from natural deposits and converted it into steel. Now the 'bugs' are ripping that steel apart, and some of that rusticle biomass is going back into pig iron"—crude, unrefined iron.

Much of the digested iron goes into the ocean environment, he noted, and eventually ends up in animals' bloodstreams or in sea plants that require iron for photosynthesis.

Even if rusticles weren't present, Titanic's hull might do a pretty good job of degrading on its own, in part because its mix of metals fosters a process called galvanic exchange.

Lead, bronze, brass, and other metals in Titanic are better than the iron that makes up most of the hull's steel at retaining their electrons.

When iron is connected to one of these other materials in an electrolyte, such as salt water, electrons flow from one metal to the next, causing iron to corrode quicker, according to the U.S. National Oceanic and Atmospheric Administration.

Currents, Humans Rub Titanic the Wrong Way?

The North Atlantic's surface was eerily calm the night Titanic sank, but strong and unpredictable currents at the seafloor are also taking a toll on the wreck.

"It's changing all the time," RMS Titanic, Inc.'s Nargeolet said of the current. "That pushing back and forth, back and forth is maybe like when a hurricane moves a tree for a few hours on one side and a few others on the other side. Finally the tree is gone.

"I could see a few holes on the deck a few years ago," he said. "Now these holes are getting really big—the current is going back and forth and working on them 24 hours a day."

Humans too may be hastening the ship's collapse—and have certainly altered its resting place.

Thousands of artifacts have been legally salvaged, for example, and an unknown number of others may have been illegally taken. Ships bearing scientists, filmmakers, and tourists have left modern trash behind. (Read "Titanic Director Films Wreck in 3-D" [2003].)

What's more, ocean explorer Robert Ballard, who led the 1985 rediscovery of the ship, and others have suggested that submersibles might have caused considerable damage to Titanic by landing on or bumping into the ship—which Expedition Titanic will be careful not to do, according to project co-leader David Gallo.

The submersibles will explore around the ship but take all possible precautions not to damage it or become tangled with the wreckage—a danger for both Titanic and the expensive equipment, said Gallo, director of special projects at Woods Hole Oceanographic Institution.

"We're going to be very careful not to touch the ship," he said. "It's like any operation or exploratory surgery: There is always some risk, but we've done everything we can to ensure that we won't in any way alter the site itself."

Expedition Titanic may also uncover solid evidence as to which past damage may have been caused by humans—until now, most such evidence has been anecdotal, Gallo said. The survey will likely identify dive weights, cables, and other modern debris that might eventually be removed.

Hard Evidence of Titanic Decay

Expedition Titanic will retrieve hard evidence of corrosion at the Titanic site—steel test platforms that look something like mini-stepladders. First deployed in 1998, the platforms have endured the same destructive conditions as Titanic itself.

Because the scientists know precisely how thick the platforms were at deployment, they allow researchers to gauge exactly how fast metal degrades at the Titanic site. "Basically we look and see how much steel is left on them," Cullimore, the microbiologist, said.

The estimated rate of decay should allow scientists to better predict just how long Titanic will remain fairly intact.

Titanic Tomb Raiders?

In addition to Woods Hole Oceanographic Institution, several other top scientific organizations are managing the data collection. But RMS Titanic, Inc.—which holds exclusive salvage rights to the wreck—is funding the endeavor.

Titanic salvage has been a controversial issue for more than two decades, with Titanic discover Ballard among the critics. (Related: "Retrieval of Titanic Artifacts Stirs Controversy.")

According to Ballard, the Titanic site should remain undisturbed as a "sacred grave" for the more than 1,500 passengers and crew who died in the waters above. Instead, salvagers, tourists, and filmmakers have "turned her into a freak show at the county fair," he's said. (Read more in an excerpt of Ballard's National Geographic magazine article "Why Is Titanic Vanishing?")

But Expedition Titanic organizers say they don't intend to raise any artifacts. "The only treasures we’re going to be looking for are treasures of the mind," project co-leader Gallo said. "And we’re not picking anything up but data."

Even so, the expedition's findings could add fuel to the salvage debate, Gallo admits.

"If we find out that the hull is going to collapse completely in the near term, what do we then think about the artifacts that are in that hull?" he said.

"Do we let it crumble naturally?" he asked. "Or do we try to somehow preserve the legacy by taking some of those pieces from the seafloor?"

Titanic: The Video Game?

When it comes to the controversial shipwreck, there's at least one thing everyone can agree on.

"I don't know of anyone that's said, Boy, the Titanic looks better than ever," Gallo said. "We know that it's deteriorating like most man-made things, which don't last long on the deep seafloor."

Expedition Titanic "is the first real attempt, in any rigorous sense, to get scientific evidence about what's happening to the ship and how fast it's happening," he added. "It's a systematic method of rigorous sampling and mapping."

Gallo hopes that the resulting 3-D archaeological model will be paired with immersive, video game-like technology that would allow people anywhere in the world to virtually explore the shipwreck for themselves.