Pressure-packed peril at oceans’ bottom

The news reports this week described the submersible Titan as “lost at sea.” That did not begin to capture the cold, darker-than-dark depths of the Atlantic Ocean. The tragedy of the Titan, the debris of which was spotted Thursday near the encrusted hulk of the Titanic, is a reminder that when humans invade exotic environments for which they are not adapted there is minimal margin for error.

The submersible, operated by the private company OceanGate as a high-priced adventure travel opportunity, was supposed to visit the Titanic, which rests on the muddy seafloor 12,500 feet below the surface of the Atlantic. But on Sunday, the submersible endured some kind of incident or malfunction and went silent 1 hour 45 minutes into its 2½-hour dive.

The very deep sea is a forbidding, almost alien environment, inhabited only by odd, eyeless creatures that have adapted to pressures that could instantly crush the most advanced Navy submarine. What’s more, the Titanic’s resting place is 370 miles from the Canadian coast, and farther than that from any port from which rescue vessels can be deployed.

These challenges made the search for the missing vessel and its five occupants akin to an effort to rescue astronauts, retired Admiral Thad Allen, former commandant of the Coast Guard, said.

“This is closer to Apollo 13 than a classic search-and-rescue mission,” Allen said. “Trying to extract a vessel from 12,000 feet is extraordinarily difficult, if not impossible.”

The Coast Guard Thursday said that the five-person crew of the Titan had been killed in a catastrophic implosion of the vessel’s pressure chamber.

The water pressure where the Titanic rests is about 6,000 pounds per square inch. By comparison, atmospheric pressure is 14.7 pounds per square inch. Pressure builds in a linear fashion as a submersible descends. At the time the Titan submersible went silent, it would have been dealing with pressures hundreds of times greater than at the surface.

To offer one visual image: The average depth of the planet’s seafloor hydrothermal vents is 7,000 feet. Researchers studying these ecosystems — where life exists using chemosynthesis rather than photosynthesis — have carried standard foam cups to such depths. The cups retain their form but are compressed to the size of a shot glass.

“I think we all agree that going somewhere that has 400 times the pressure in the atmosphere is a dangerous thing to be doing,” said Jules Jaffe, research oceanographer emeritus at Scripps Institution of Oceanography, part of the University of California San Diego.

But he supports exploration of this kind and pointed out that another private company, Triton Submarines, has successfully ferried tourists to the bottom of the Mariana Trench, the deepest spot in any ocean, nearly seven miles below the surface.

“Obviously [the Titan submersible] worked for a while, and they had some number of successful dives. But as they continued to use it, there is a chance that the mechanical properties became fatigued,” Jaffe said.

Lisa Levin is a veteran oceanographer and deep-sea biologist at Scripps who has plunged into that strange world many times. She studies the bizarre chemosynthetic organisms feeding off methane leaking from the seafloor along continental margins. She has made 53 dives on the famed Alvin submersible that has been in operation, with many upgrades and inspections, since the 1960s.

She once was at almost 5,000 feet on an undersea mountain off the coast of Mexico when everything went dark. The pilot fiddled with electrical wiring and couldn’t get it lit up again, and so they quickly resurfaced.

She said she does not like talking about things that can go wrong. But in the case of the Titan, she said Wednesday, she feared that something might have happened suddenly and catastrophically, such as an implosion. Had there been a gradual leak, the mission would have been quickly aborted. Getting snagged in a net or otherwise stuck somewhere should not have ended communication with the expedition ship at the surface, she said.

“I’m guessing whatever happened, happened quickly,” she said.

Many submersibles have ventured into the deepest parts of the sea. James Cameron, the director of the blockbuster movie “Titanic,” is among those who have managed a close-up look at the doomed ocean liner via submersible. Cameron has made that same dive dozens of times, as well as a 2012 dive to the Mariana Trench.

But risk does not evaporate with each successful venture. Engineers know that risk builds like plaque, and complex technology deployed in harsh environments — such as space or the deep sea — can fail in many ways not easily envisioned.

The NASA space shuttle program carried with it known risks of disaster. The Challenger met a catastrophic end just minutes after launch when a component of a solid rocket booster failed, leading to the ignition of the external fuel tank. The Columbia was destroyed by the heat of atmospheric reentry penetrating the leading edge of a wing damaged at launch.

The Titan submersible was a prototype craft, and the OceanGate journeys are a form of adventure travel that exists beyond the reach of government regulatory agencies, said Allen. This is not a situation where agencies have vessels standing by, ready to conduct rescue operations on choppy seas in hurricane season in the middle of the Atlantic Ocean.

“We’re dealing with the high seas and the depths of the ocean — they’re one of the few ungoverned places on Earth,” said Allen, who knows a thing or two about offshore disasters, having served as the no-nonsense national incident commander for the response to the 2010 BP oil spill.

The depths of the Atlantic can’t be reached by human divers without specially designed submersibles. The creatures of the deep are adapted to the pressure, the cold, and other extreme conditions, such as low oxygen levels or high levels of hydrogen sulfide.

Levin, the veteran deep ocean explorer, points out that humans never experience those conditions directly.

“As a scientist, diving in a submarine, other than being a little bit cold, we don’t experience the high pressure and the other challenges in the water,” she said. “We build submarines to keep the internal environment comfortable for us.”

And they trust the technology to work — knowing that there may come a moment when it doesn’t.