2023-06-22 07:46:49
The disappearance of the Titan submersible during a trip to the wreckage of the Titanic raises questions about the risks involved in an expedition to the depths of the ocean.
Sometime in the fall of 1911, a huge chunk of ice broke off a glacier in the southwest of the vast Greenland ice sheet. Over the next few months, the iceberg slowly drifted south, gradually melting as it was carried by ocean currents and wind.
On the cold, moonless night of April 14, 1912, a 400-foot-long iceberg, all that remained of the estimated 1,650-foot chunk of ice that had broken off Greenland the previous year, collided with the RMS Titanic.
The ship was making its maiden voyage from the British city of Southampton to New York. In less than three hours the ship had sunk, dragging more than 1,500 passengers and crew to their deaths.. The wreck of the Titanic is now almost 3.8 km deep and almost 640 km southeast of the coast of Newfoundland in Canada.
Icebergs still pose a danger to shipping: In 2019, 1,515 icebergs moved far enough south to enter transatlantic shipping lanes during the months of March through August.
But Titanic’s final resting place carries dangers of its ownwhich means that visits to the world’s most famous shipwreck present a significant challenge.
After the disappearance of the commercial submersible for five people that carried passengers to the remains of the Titanic, the BBC analyzes what this region of the ocean floor is like.
OCEANGATE
sailing in the depths
The deep ocean is dark. Sunlight is absorbed very quickly by water and cannot penetrate much further than 1,000 meters from the surface. Beyond this point, the ocean is in perpetual darkness.. The Titanic lies within a region known as the “midnight zone” for this very reason.
Previous expeditions to the wreck site have described how after descending for more than two hours through total darkness, the ocean floor suddenly appears under the lights of the submersible.
With a limited viewing horizon beyond the few meters illuminated by the submersible’s lights, navigation at this depth is challenging and it is easy to become disoriented on the seafloor.
However, detailed maps of the Titanic wreck site produced from decades of high-resolution scanning can provide landmarks as objects are spotted. Sonar also allows the crew to detect features and objects beyond the submersible’s small beam of light.
Submersible pilots also rely on a technique known as inertial navigationwhich uses a system of accelerometers and gyroscopes to track its position and orientation relative to a known starting point and velocity.
OceanGate’s Titan submersible carries a state-of-the-art autonomous inertial navigation system that is combined with an acoustic sensor known as a Doppler Velocity Log to estimate the depth and velocity of the vehicle relative to the seabed.
Even so, passengers aboard previous OceanGate Titanic voyages have described how difficult it is to find your way once you reach the bottom of the ocean.
The Titanic lies within a region known as the “midnight zone”GETTY IMAGES
Mike Reiss, a TV sitcom writer who worked on The Simpsons and was on a trip with OceanGate to the Titanic last year, told the BBC: “When you hit rock bottom you don’t really know where you are. We had to fumble at the bottom of the ocean knowing that the Titanic was somewhere there. But it was so dark that something that big was only about 1,500 feet away and we spent 90 minutes looking for it.”
The deeper an object is in the ocean, the greater the pressure of the water around it. On the seabed 3,800 meters underwater, the Titanic and everything around it supports pressures of around 40 MPa, which is 390 times greater than those on the surface.
“To put that in perspective, it’s about 200 times the pressure in a car tire,” Robert Blasiak, an ocean researcher at the Stockholm Resilience Center at Stockholm University, told the show. Today from BBC Radio 4.
“That’s why you need a submersible that has really thick walls,” he added.
The Titan submersible’s carbon fiber and titanium walls are designed to give it a maximum operating depth of 4,000 meters.
Microbes feeding on the ship’s iron are accelerating the deterioration of the wreck
The strong surface currents that can divert boats and bathers are probably more familiar to us, but the depths of the ocean are also swept by underwater currents.
Although these currents are usually not as strong as those found on the surface, they can still involve the movement of large amounts of water.
Currents can be driven by surface winds affecting the water column below, deep-sea tides, or differences in water density caused by temperature and salinity, known as thermohaline currents.
Rare events known as benthic stormswhich are generally associated with eddies at the surface, can also cause powerful and sporadic currents capable of carrying material on the seafloor.
The information that exists on the submarine currents around the Titanic, which split into two main sections after bow and stern broke off while sinkingcomes from research studying patterns on the seabed and the movement of squid around the wreck.
Some of the Titanic’s wreckage is known to lie near a section of the seafloor affected by a southward-flowing current of cold water known as the Western Boundary Undercurrent, Western Boundary Undercurrent.
The flow of this “bottom current” creates migrating dunes, ripples, and ribbon-like patterns in the sediment on the ocean floor that have given scientists an idea of its strength.
Most of the formations that have been observed on the seabed are associated with relatively weak to moderate currents.
Ripples in the sand along the eastern edge of the Titanic debris field (remnants of belongings, accessories, coal, and parts of the ship itself that were scattered when the ship sank) indicate an east-west current.
But the scientists note that at the main wreck site, currents tend to flow from northwest to southwest, perhaps because larger pieces of wreck alter their direction.
Expeditions over the years have studied the ocean currents at the resting place of the shipSCIENCE PHOTO LIBRARY
To the south of the bow section, the currents appear particularly changeable, running from northeast to northwest to southwest. many experts they hope that the action of these currents will eventually bury the remains of the Titanic in sediments.
Gerhard Seiffert, a deep-sea marine archaeologist who recently led an expedition to scan the Titanic wreck in high resolution, told the BBC he didn’t think the currents in the area were strong enough to pose a risk to a submersible. , as long as it has power.
“I am not aware of the currents posing a threat to any deep-sea vehicles in operation at the Titanic site,” Seiffert said. “The currents…in the context of our project posed a challenge for precision mapping, not a safety risk.”
During its more than 100 years at the bottom of the sea, the remains of the Titanic have gradually degraded. The initial impact of the two main parts of the vessel against the seabed twisted and distorted large sections of the wreckage.
Over time, microbes that feed on the ship’s iron have formed what are known as “rusticles,” rust shaped like icicles (sharp bits of ice) and are accelerating the deterioration of the wreck.
In fact, scientists estimate that the increased bacterial activity at the stern of the ship, largely due to the increased level of damage it sustained, is causing it to deteriorate 40 years faster than the bow section.
“The wreck is constantly collapsing, mainly due to corrosionsays Seiffert. “Every year a little. But as long as you keep a safe distance, no direct contact, no penetration through the openings, there is no danger.”
Although extremely unlikely, sudden sediment flows along the seafloor are known to have damaged and even washed away man-made objects lying on the ocean floor in the past.
The largest of these flash flows, like the one that severed the transatlantic cables off the coast of Newfoundland in 1929, are triggered by seismic events such as earthquakes.
There is a growing appreciation of the risk posed by these events, although there are no indications that a similar one was involved in the disappearance of the Titan submersible.
Scientists have identified indications that the seabed around the Titanic wreck has been hit by huge underwater landslides in the distant past.
Huge volumes of sediment appear to have cascaded down the continental slope from Newfoundland to create what scientists call a “instability corridor”.
The researchers estimate that the last of these “destructive” events occurred tens of thousands of years ago, creating layers of sediment up to 100 meters thick.
But these events happen very rarely, says David Piper, a marine geology researcher with the Geological Survey of Canada, who has spent many years studying the seafloor around the Titanic.
Piper compares such events to the eruption of Mount Vesuvius or Mount Fuji in terms of the frequency with which they can occur, on the order of once every tens of thousands to hundreds of thousands of years.
The Titanic in a Belfast shipyard in 1911. The ship sank in less than three hours, dragging more than 1,500 people to their deathsGETTY IMAGES
Other events known as turbidity currentsOccurring when water is laden with sediment by continental slope flow, they are more common and can be triggered by storms.
“We show a repeat interval of perhaps 500 years,” Piper says. But the topography of the seabed in the area would likely divert any sediment flow toward a site known as “Titanic Valley,” meaning it would not reach the wreck.
Both Seiffert and Piper say that such an event is unlikely to have played a role in the disappearance of the Titan submersible.
There are other geological features around the wreck site that have yet to be explored. On a previous expedition to the Titanic with OceanGate, Paul-Henry Nargeolet (one of the missing), a former French Navy submersible pilot and diver, tracked down a mysterious signal he had detected with sonar in 1996.
The signal turned out to be a rocky reef, covered in marine life. Nargeolet was hoping to investigate another signal he had detected near the Titanic wreck on recent expeditions. As he continues to search for the missing submersible, there are few clues as to what might have happened to the Titan and her crew.
But in such a challenging and inhospitable environment, the risks of visiting the Titanic’s wreckage are as relevant today as they were in 1986, when the first people to see the ship since it sank made the journey into the depths.
Por Richard Gray
BBC News World
BBC MundoConocé The Trust Project
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