Key Points
- Underwater noises have reportedly been heard during the search for the missing submersible.
- The submersible was exploring the Titanic wreckage when it went missing off the Canadian coast.
- Search and rescue efforts are continuing for a fourth day.
The rescue effort for a missing submersible near the wreck of the Titanic has entered a critical phase, as the 96 hours that the crew were expected to have oxygen for have now lapsed.
They have been missing for over four days.
Experts have emphasised that it is an imprecise estimate and could be extended if the five people on board have taken measures to conserve oxygen.
It is not known if they have survived.
Rescuers are concentrating their efforts on a remote area of the North Atlantic where a series of undersea noises have been detected although officials caution the sounds may not have originated from the vessel.
An international coalition of rescue teams has swept a vast expanse of the ocean for signs of the Titan, which disappeared on Sunday (local time) while heading deep into the ocean to visit the century-old wreck as part of a tourist expedition.
The passengers are bolted into the vessel from the outside, with 17 bolts holding the hatch in place, CBS reporter David Pogue, who has been on the vessel before, said.
"Even if our folks are at the surface and running out of air — even if they can see the air through the plexiglass window — they can't get to it," he said.
"They would have to be unbolted from the outside. That, to me, is a horror story."
How is the search operation being carried out?
The US coast guard said remotely operated vehicle (ROV) searches were deployed in the area where Canadian aircraft recorded the noises using sonar buoys on Tuesday and Wednesday (local time).
The French research ship , equipped with a robotic diving craft capable of reaching depths even below the Titanic wreck, below the surface, was moving into the area.
Credit: SBS News
US coast guard captain Jamie Frederick said at a press conference that analysis of the noises has been "inconclusive".
"We don't know what they are, to be frank with you," he said.
"We're searching in the area where the noises were detected."
What happens after the submersible is found?
Even if the submersible is located, retrieving it presents huge logistical challenges, given the extreme conditions and kilometres below the surface.
Teams from the United States, Canada and France have searched more than 25,900 square km of open sea, roughly the size of Lebanon.
The 6.7-metre submersible Titan, operated by US-based OceanGate Expeditions, began its descent at 8am on Sunday (local time).
It lost contact with its parent surface vessel during what should have been a two-hour dive to the Titanic.
The submersible had 96 hours of air, according to the company's specifications, which would mean the oxygen could run out by Thursday morning.
But experts say the air supply depends on a range of factors, including whether the submersible remains intact and still has power.
Who is on board the submersible?
Those aboard the submersible, the highlight of a tourist adventure that costs $US250,000 ($367,000) per person, included British billionaire and adventurer Hamish Harding, 58, and Pakistani-born businessman Shahzada Dawood, 48, with his 19-year-old son Suleman, who are both British citizens.
French explorer Paul-Henri Nargeolet, 77, and Stockton Rush, founder and chief executive of OceanGate Expeditions, were also reported to be on board.
A friend of Harding, Jannicke Mikkelsen, who has accompanied the entrepreneur on other expeditions, said she was hoping for good news but was not optimistic.
"It would be a miracle if they are recovered alive," she said.
Mr Harding's stepson wrote on Facebook that Mr Harding had "gone missing on submarine" and asked for "thoughts and prayers".
The stepson subsequently removed the post, citing respect for the family's privacy.
British billionaire Hamish Harding is among the passengers on board the submarine. Source: Facebook / Hamish Harding
There have been no further posts from him.
Mr Harding is a holder of three Guinness World Records: longest duration at full ocean depth by a crewed vessel, longest distance traversed at full ocean depth by a crewed vessel and fastest circumnavigation via both poles by aeroplane.
Two of these feats were achieved by Harding and ocean explorer Victor Vescovo when they dived to the lowest depth of the Mariana Trench - the deepest part of the ocean - in a two-person deep-submergence vehicle in March 2021.
In June last year, Mr Harding travelled to space with fellow billionaire .
What does a dive to see the Titanic's wreck involve?
The expeditions start in St John's, Newfoundland, before heading out approximately 640km into the Atlantic to the wreckage site, according to OceanGate's website.
To visit the wreck, passengers climb inside Titan, the five-person submersible, which takes two hours to descend approximately 3800m to the Titanic.
The Titanic passenger ship f after striking an iceberg, killing more than 1,500 people.
What issues could rescuers face?
Rescuers face significant obstacles both in finding the Titan and in saving the people aboard, according to experts.
If the submersible experienced an emergency in mid-dive, the pilot would likely have released weights to float back to the surface, according to Alistair Greig, a professor of marine engineering at University College London.
But absent communication, locating a van-sized submersible in the vast Atlantic Ocean could prove challenging, he said.
The submersible is sealed with bolts from the outside, which means the occupants cannot escape without assistance even if it surfaces.
If the Titan is on the ocean floor, a rescue effort would be even more challenging due to the extreme conditions below the surface.
The Titanic lies approximately 3,800 metres underwater, where light does not penetrate.
Only specialised equipment can reach those depths without getting crushed by the massive water pressure.
"It's really a bit like being an astronaut going into space," said Tim Matlin, a Titanic expert.
"I think if it's on the seabed, there are so few submarines that are capable of going that deep. And so, therefore, I think it was going to be almost impossible to effect a sub-to-sub rescue."
