All five passengers aboard Titan, a submersible missing near the wreck of the Titanic, had died — likely in an instant — after their vessel suffered what the US Coast Guard said Thursday (22 June) was a “catastrophic implosion” in the ocean depths.

The somber announcement ended a multinational search-and-rescue operation that captivated the world since the tiny tourist craft went missing in the North Atlantic four days ago.

Rear Admiral John Mauger told reporters in Boston that analysis showed debris found on the seafloor, 1,600 feet (500 metres) from the bow of the Titanic, was consistent with the implosion of the submersible’s pressure chamber.

“On behalf of the United States Coast Guard and the entire unified command, I offer my deepest condolences to the families,” Mauger said.

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US Rear Admirak John Mauger, the First Coast Guard District commander, speaks at a press conference at the US Coast Guard Base Boston in Boston, Massachusetts. Debris discovered on the ocean floor suggests the missing submersible near the wreck of the Titanic suffered a “catastrophic loss” of pressure, Mauger said. (Image: Joseph Prezioso/ AFP)

The passengers on board Titan were British explorer Hamish Harding, French submarine expert Paul-Henri Nargeolet, Pakistani-British tycoon Shahzada Dawood and his son Suleman, and Stockton Rush, CEO of the sub’s operator OceanGate Expeditions.

OceanGate said its “hearts are with these five souls and every member of their families during this tragic time.”

“These men were true explorers who shared a distinct spirit of adventure, and a deep passion for exploring and protecting the world’s oceans,” it said in a statement. “We grieve the loss of life and joy they brought to everyone they knew.”

The Coast Guard announced earlier Thursday that an underwater robot had discovered a “debris field” in the search area. Authorities said they later learned the pieces included the sub’s tail cone and front and back ends of its pressure hull.

What exactly happened to Titan, the Titanic submersible, and its passengers?

Mauger said the Coast Guard could not be sure when or why the vessel imploded and declined to be drawn on whether remains of the men would be retrieved. “This is an incredibly unforgiving environment down there on the seafloor,” he said.

The process of demobilising personnel and vessels from the scene would soon begin but unmanned robots would continue operations on the seabed for now, Mauger added. “We’ll collect as much information as we can.”

The US military originally detected the likely implosion of the craft on secret underwater sound monitoring devices shortly after it went missing on Sunday, the Wall Street Journal reported Thursday.

“The US Navy conducted an analysis of acoustic data and detected an anomaly consistent with an implosion or explosion in the general vicinity of where the Titan submersible was operating when communications were lost,” a unnamed senior Navy official told the Journal.

OceanGate Expeditions’ Titan submersible beginning a descent in an undated photo. (Image: AFP Photo/ OceanGate Expeditions)

The small submersible named Titan disappeared on Sunday as it descended to the Titanic, which sits more than two miles (nearly four kilometres) below the ocean’s surface and 400 miles off the coast of Newfoundland, Canada.

OceanGate Expeditions charged USD 250,000 (SGD 337,000) for a seat on the sub. In a 2018 lawsuit, its former director of marine operations raised concerns about the “experimental and untested design” of Titan.

Harding was a billionaire and keen explorer with three Guinness Records to his name, while the Dawoods belonged to one of Pakistan’s richest families. Nargeolet was nicknamed “Mr Titanic” for his frequent dives at the site.

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From left to right: Titan’s passengers were Stockton Rush, Paul-Henri Nargeolet, Shahzada Dawood and Hamish Harding. Dawood’s son Suleman was also aboard the submersible. (Image: AFP Photo/ OceanGate Expeditions, Joel Saget/ AFP, World Economic Forum, AFP Photo/ Dirty Dozen Productions)

The British and Pakistani governments expressed their “deepest condolences” to all the men’s families.

The search for Titan after the submersible went missing en route to the Titanic wreck

The 21-foot (6.5-metre) Titan had been due to resurface seven hours after beginning its descent at 8:00 am on Sunday. But the craft lost communication with its mothership less than two hours in.

Ships and planes from the US and Canadian coast guards, as well as a robot sent from France, scoured 10,000 square miles (around 20,000 square kilometres) of surface water — roughly the size of the US state of Massachusetts — for the vessel.
The search honed in on areas where underwater banging noises were detected late Tuesday and Wednesday. But Mauger said that ultimately the sounds did not appear to have any relation to the site of the debris.

The Titanic hit an iceberg and sank in 1912 during its maiden voyage from England to New York with 2,224 passengers and crew on board. More than 1,500 people died.

A view of the Titanic from within Titan, the doomed submersible. (Image: OceanGate Expeditions)

It was found in 1985 and remains a lure for nautical experts and underwater tourists. The pressure at that depth as measured in atmospheres is 400 times what it is at sea level.

Marine scientist and oceanographer David Mearns, who specialises in deep water search and recovery operations, said earlier the debris discovery indicated a rapid breakup of the submersible.

“The only saving grace about that is that it would have been immediate, literally in milliseconds, and the men would have had no idea what was happening,” Mearns, who was friends with two of those onboard, told Sky News.

What is a “catastrophic implosion”?

A “catastrophic implosion,” such as that believed to have destroyed the Titan submersible, would have happened with incredible force and speed given the crushing water pressure on the floor of the ocean.

The remains of the Titanic rest on the seabed in the North Atlantic at a depth of some 3,800 meters (12,400 feet). At sea level, atmospheric pressure is 14.7 pounds per square inch (psi). Water pressure at the depth where the ocean liner lies is equivalent to around 400 atmospheres, nearly 6,000 psi.

As a comparison, the bite of a large great white shark exerts a force of nearly 4,000 psi, according to Scientific American. In an implosion caused by a defect in the hull or for some other reason, the submersible would collapse in on itself in milliseconds, crushed by the immense water pressure. Death would be virtually instantaneous for the occupants of the pressurised chamber.

The Titan, built by OceanGate Inc. of Everett, Washington, was designed to sustain the extreme water pressure at the depth of the Titanic and had made previous dives to the wreck.

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Titan on one of its previous Titanic expeditions. (Image: OceanGate Expeditions)

But safety concerns had been raised, most notably in a lawsuit involving OceanGate’s former director of marine operations, David Lochridge, who was fired in 2018 after warning about the Titan’s “experimental” carbon fibre hull.

Roderick Smith, an engineering professor at Imperial College, London, said the accident was likely due to a “failure of the pressure hull,” but debris will need to be recovered to carry out a full investigation.

And even then it may be difficult to pinpoint the cause. “The violence of the implosion means that it may be very difficult to determine the sequence of events,” Smith said.

This story was published via AFP News

(Main and Featured images: AFP Photo, OceanGate Expeditions)