Friday, June 23, 2023

What we know about the ocean’s depths — and why it’s so risky to explore it

Jackie Wattles CNN
Fri, June 23, 2023 

The submersible vehicle that was lost at sea is part of a relatively new effort enabling tourists and other paying customers to explore the depths of the ocean, the vast majority of which has never been seen by human eyes.

Though people have been exploring the ocean’s surface for tens of thousands of years, only about 20% of the seafloor has been mapped, according to 2022 figures from the National Oceanic and Atmospheric Administration.

Researchers often say that traveling to space is easier than plunging to the bottom of the ocean. While 12 astronauts have spent a collective total of 300 hours on the lunar surface, only three people have spent around three hours exploring Challenger Deep, the deepest known point of Earth’s seabed, according to the Woods Hole Oceanographic Institution.

In fact, “we have better maps of the moon and Mars than we do of our own planet,” said Dr. Gene Feldman, an oceanographer emeritus at NASA who spent more than 30 years at the space agency.

There’s a reason deep-sea exploration by humans has been so limited: Traveling to the ocean’s depths means entering a realm with enormous levels of pressure the farther you descend — a high-risk endeavor. The environment is dark with almost no visibility. The cold temperatures are extreme.

The submersible, which is believed to have been destroyed in a catastrophic implosion, killing all five people aboard, was en route to explore the wreckage of the RMS Titanic. The remnants of the ship lie about 900 miles (1,450 kilometers) off the coast of Cape Cod, Massachusetts, and about 12,500 feet (3,800 meters) underwater. Operated by OceanGate Expeditions, a private company based in Washington state, the tourist vessel lost contact with its mother ship after departing on Sunday.

The US Navy later revealed that it had detected a sound on Sunday that would match an implosion, indicating the vessel, called the Titan, was rapidly destroyed. The disaster could have occurred during the submersible’s descent, as pressure on the vehicle grew.

Many of the factors that made the multiday search for the vessel so difficult are also the reasons a comprehensive exploration of the ocean floor remains elusive.

“Aquatic search is pretty tricky, as the ocean floor is a lot more rugged than on land,” said Dr. Jamie Pringle, a reader in forensic geoscience at England’s Keele University, in a statement.

In the days before the submersible’s likely implosion was confirmed, search and rescue teams relied on sonar, a technique that uses sound waves to explore the opaque depths of the ocean, to attempt to pinpoint the vehicle in case it had been stranded on the seafloor. The challenging process requires a very narrow beam with a high frequency to offer a clear picture of where objects might be.
A history of ocean exploration

The first submarine was built by Dutch engineer Cornelis Drebbel in 1620, but it stuck to shallow waters. It would take nearly 300 years — in the aftermath of the Titanic disaster — before sonar technology began to offer scientists a clearer picture of what lies in the ocean’s depths.

A major step forward in human exploration came in 1960 with the historic dive of the Trieste bathyscaphe, a type of free-diving submersible, to the Challenger Deep, located more than 35,800 feet (10,916 meters) underwater.


Explorer and physicist Auguste Piccard is seen wearing a life jacket as he emerges from the bathyscaphe Trieste, which he designed, after making a world record dive of 10,335 feet (3,150 meters) on October 3, 1953. The dive was made off the west coast of Italy. -
Keystone/Hulton Archive/Getty Images

Only a few missions since have returned to such depths. And the trips are extremely dangerous, Feldman said.

For every 33 feet (10 meters) traveled beneath the ocean’s surface, the pressure increases by one atmosphere, according to NOAA. An atmosphere is a unit of measure that’s 14.7 pounds per square inch. That means a trip to the Challenger Deep can put a vessel under pressure that is “equivalent to 50 jumbo jets,” Feldman noted.

At high pressure, the tiniest structural defect can spell disaster, Feldman added.

During the 1960 dive of the Trieste, passengers Jacques Piccard and Don Walsh said they were stunned to see living creatures.

“Right away, all of our preconceptions about the ocean were blown out the window,” Feldman said.

What lies at the bottom of the ocean


While what’s considered the deep ocean extends from 3,280 feet to 19,685 feet (1,000 meters to 6,000 meters) beneath the surface, deep-sea trenches can plunge to 36,000 feet (11,000 meters), according to the Woods Hole Oceanographic Institution in Massachusetts. This region, called the hadal or hadalpelagic zone, is named for Hades, the Greek god of the underworld. In the hadal zone, the temperatures are just above freezing, and no light from the sun penetrates.

Scientists were first able to prove that life existed below 19,685 feet in 1948, according to the institution.

Discoveries at the Challenger Deep have been remarkable, including “vibrantly colorful” rocky outcrops that could be chemical deposits, prawnlike supergiant amphopods, and bottom-dwelling Holothurians, or sea cucumbers.

Feldman also remembers his own attempt in the 1990s to catch a glimpse of the evasive giant squid, which lurks in the inky depths of the ocean. The first video of a live creature, which can grow to nearly 60 feet (18 meters) long, was captured in the deep sea near Japan in 2012, according to NOAA.

A new world also opened in the 1970s, Feldman said, when “an entirely alien ecosystem” was discovered by marine geologist Robert Ballard, then with the Woods Hole Oceanographic Institution, within the sea near the Galápagos Rift — “with these giant worms, giant clams, and crabs and things that lived at these … vents under the sea.”


A female deep-sea anglerfish attracts prey with a lure projecting from her head in the Atlantic Ocean. - Bluegreen Pictures/Alamy Stock Photo

The unusual creatures — some of which glow with bioluminescence to communicate, lure prey and attract mates — have carved out habitats within the steep walls of ocean trenches. These life forms have adapted to live in the extreme environment and don’t exist anywhere else on the planet. Instead of relying on sunlight for fundamental processes, they use chemical energy belched out from hydrothermal seeps and vents formed by magma rising from beneath the ocean floor.

The chilly seawater seeps through seafloor cracks and becomes heated to 750 degrees Fahrenheit (400 degrees Celsius) as it interacts with the magma-heated rocks. The chemical reactions produce minerals containing sulfur and iron, and the vents spew out the nutrient-rich water that supports the ecosystem of unusual marine life clustered around them.

Researchers have used the submersible Alvin to discover strange sea life, study plate tectonics and hydrothermal vents — and to explore the Titanic in 1986 after Ballard located the famed shipwreck.

Researchers from the WHOI and NASA have collaborated to develop uncrewed autonomous underwater vehicles that can descend through the tricky terrain of the trenches and withstand pressures greater than 1,000 times that at the ocean’s surface. The vehicles can investigate the diversity of life within the trenches, and they could also help scientists explore oceans on the moons around Jupiter and Saturn in the future.


A giant isopod is a deep-sea crustacean. 
- Alessandro Mancini/Alamy Stock Photo


Why mapping the ocean is so challenging

From a strictly scientific perspective, touristic trips to the ocean floor do little to advance our understanding of the ocean’s mysteries.

“Humans like superlatives,” Feldman said. “We want to go to the highest, the lowest, the longest.”

But only a “very small percentage of the deep ocean, and even the middle ocean, has been seen by human eyes — an infinitesimal amount. And a very, very small amount of the ocean floor has been mapped,” he added.

The reason, Feldman noted, largely comes down to cost. Boats equipped with sonar technology can rack up exorbitant expenses. Fuel alone can total up to $40,000 per day, Feldman said.

There is, however, currently an effort underway to create a definitive map of the ocean floor, called Seabed 2030.

Still, there are huge gaps in what’s known of the deep sea. Of the 2.2 million species believed to exist in Earth’s oceans, only 240,000 have been described by scientists, according to the Ocean Census, an initiative to record and discover marine life.

However, it’s impossible to know for certain just how many sea creatures exist, Feldman noted.



Most of the seafloor explored during Dive 07 of the 2019 Southeastern US Deep-sea Exploration, conducted by NOAA and its partners, was covered with these manganese nodules, the subject of the Deep Sea Ventures pilot test nearly five decades ago. - Courtesy NOAA Office of Ocean Exploration/Research, 2019 Southeastern U.S. Deep-sea Exploration

“We can make estimates all the time but then … you go somewhere new and discover an entirely new genus or an entirely new way of living,” he said.

Advances in technology may make human exploration of the ocean depths unnecessary. Innovations such as deep-sea robots, high-resolution underwater imaging, machine learning, and sequencing of DNA contained in seawater will help accelerate the speed and scale of discovery of new life forms.

“We have better maps of the moon’s surface than of the seafloor because seawater is opaque to radar and other methods we use to map land,” said marine ecologist Alex Rogers, a professor of conservation biology at the University of Oxford in the United Kingdom. “However, 150 years of modern oceanography have led to better understanding of many aspects of the ocean such as the life it contains, its chemistry and its role in the Earth system.”

Mapping the ocean “helps us to understand how the shape of the seafloor affects ocean currents, and where marine life occurs,” Rogers added. “It also helps us to understand seismic hazards. So it is basic fundamental science of overwhelming importance to human well-being.”
Human health and scientific research

The ocean is thought to be a gold mine of compounds, and its exploration has led to several biomedical breakthroughs.

The first marine-derived drug, Cytarabine, was approved in 1969 for the treatment of leukemia. The medication was isolated from a marine sponge.

Work on bioactive compounds in the venom of cone snails, a type of sea mollusk, led to the development of a potent pain reliever called ziconotide (commercially known as Prialt).

Scientists developed PCR, or polymerase chain reaction, a technique widely used to copy strands of DNA, with the help of an enzyme isolated from a microbe found in marine hydrothermal vents. And a green fluorescent protein observed in jellyfish allows researchers to watch once-invisible processes, including the spread of cancer cells and the development of nerve cells.

These are just a few examples. Researchers say the ocean and the life it contains could provide answers to some of medicine’s biggest challenges, such as antibiotic drug resistance. Studying the sea can also tell us about how life evolved.

“The ocean contains many more of the deep branches of life that have evolved over 4 billion years on Earth and so marine life can tell us a lot about the evolution of both whole organisms and specific biological systems such as developmental genes and immune system,” Rogers said via email.


6 incredible facts about the Challenger Deep, the deepest point on Earth


Jackie Wattles
Fri, June 23, 2023 

Just as Earth’s land surface has enormous peaks and valleys, the oceanic world has similarly varied topography.

Perhaps the most intriguing of these features is the Mariana Trench — a chasm in the western Pacific Ocean that spans more than 1,580 miles (2,540 kilometers) and is home to the Challenger Deep, the deepest known point on Earth’s surface that plunges more than 36,000 feet (about 11,000 meters) underwater.

That’s nearly three times deeper than the site where the wreckage of the RMS Titanic lies in the Atlantic Ocean, and it’s deeper than Mount Everest is tall.

Here are some fascinating facts about this deep-sea phenomenon.

1. ‘Titanic’ director James Cameron is one of the few people who have visited

Few human expeditions have ventured to the Challenger Deep.

The first came in 1960 with the historic dive of the Trieste bathyscaphe, a type of free-diving submersible. During the dive, passengers Jacques Piccard and Don Walsh said they were stunned to see living creatures where scientists once imagined it was impossible for anything to survive.

“Right away, all of our preconceptions about the ocean were blown out the window,” Dr. Gene Feldman, an oceanographer emeritus at NASA, previously told CNN. He spent more than 30 years at the space agency.



Deep-sea explorer and Academy Award-winning filmmaker James Cameron sits in a scale model of the Deepsea Challenger's pilot chamber at an exhibition about his history-making ocean expeditions in Sydney on May 28, 2018. - Saeed Khan/AFP/Getty Images

James Cameron, director of the 1997 film “Titanic,” was the next deep-sea explorer to follow. He piloted a submersible — one that he personally had helped design — to about 35,787 feet (10,908 meters), setting a world record in 2012.

2. A plastic bag was found in the trench

Another explorer who returned to the site was Victor Vescovo, a Texas investor who journeyed 35,853 feet (10,927 meters) down and claimed a world record in 2019.

Vescovo gave depressing insight into humankind’s impact on these seemingly untouchable remote locations when he observed a plastic bag and candy wrappers at the bottom of the Mariana Trench.

A handful of explorers have trekked to the Challenger Deep since then, but the expeditions are not common — and the journey is extremely dangerous.


Explorer and Texas investor Victor Vescovo said he saw a plastic bag and candy wrappers at the bottom of the Mariana Trench. - Atlantic Productions for Discovery Channel

For every 33 feet (10 meters) traveled beneath the ocean’s surface, the pressure on an object increases by one atmosphere, according to National Oceanic and Atmospheric Administration. An atmosphere is a unit of measure that’s 14.7 pounds per square inch. A trip to the Challenger Deep can put a vessel under pressure that is “equivalent to 50 jumbo jets,” Feldman noted.

3. It lies in the hadal zone, named for the god of the underworld

Much like the Earth’s atmosphere, the ocean can be described in terms of layers.

The uppermost portion is called the epipelagic zone, or the sunlight zone, and extends just 660 feet (200 meters) below the water’s surface, according to NOAA.

The mesopelagic zone, or the so-called twilight zone, stretches from the end of the sunlight zone to about 3,300 feet (1,000 meters).



ROV Deep Discoverer images a newly discovered hydrothermal vent field at Chamorro Seamount, which is located west of the Mariana Trench. - NOAA Office of OER/2016 Deepwater Exploration of the Marianas

Then there’s the bathypelagic zone, also called the midnight zone, and, beneath that, the abyssopelagic zone — as in, the abyssal zone — that extends from 13,100 feet (4,000 meters) to 19,700 feet (6,000 meters). That’s nearly 4 miles underwater. Within the abyssal zone, few life-forms can survive, the water is completely devoid of light, and temperatures are near freezing.

But the Challenger Deep lies even further — in the hadalpelagic zone, or the hadal zone. It’s named for Hades, the Greek god of the underworld thought to rule over the dead.

4. It’s home to unique aquatic life and mud volcanoes

The hadal zone is one of the least explored habitats on Earth. At bone-crushing depths with no sunlight, it was long thought that nothing could survive there.

But that belief has been dispelled.

“Even at the very bottom, life exists. In 2005, tiny single-celled organisms called foraminifera, a type of plankton, were discovered in the Challenger Deep,” according to NOAA.



A hydrothermal-vent chimney belches nutrient-rich fluid, which appears as dark smoke (center) due to its high levels of minerals and sulfides. The chimney is crawling with Chorocaris shrimp and Austinograea wiliamsi crabs. - NOAA Office of OER/2016 Deepwater Exploration of the Marianas

Discoveries at the Challenger Deep have included colorful rocky outcrops and bottom-dwelling sea cucumbers.

A series of undersea mud volcanoes and hydrothermal vents in the Mariana Trench also support unusual life-forms, according to NOAA. Despite the highly acidic and infernally hot water produced by hydrothermal vents in mud volcanoes, exotic species and microscopic organisms there are able to survive.

In the absence of sunlight, the creatures instead benefit from the nutrient-rich waters belched out from hydrothermal vents. The life-supporting medium results from chemical reactions between the seawater and magma rising from beneath the ocean floor.

5. The Mariana Trench was designated as a US national monument in 2009

The Marianas Trench Marine National Monument was established in 2009, in part to protect the rare organisms that thrive within its depths.

Objects of interest include the submerged ecosystem and its life-forms, such as deep-sea shrimp and crabs, and — higher up in the water column — stony coral reefs.

“A great diversity of seamount and hydrothermal vent life (is) worth preservation,” according to NOAA.

The entire national monument protects about 95,000 square miles (246,049 square kilometers).

This stunning sea jelly was seen while exploring the Enigma Seamount at 12,139 feet (3,700 meters) in the Marianas Trench Marine National Monument. - NOAA Office of OER/2016 Deepwater Exploration of the Marianas

6. It’s difficult to know just how deep the trench goes

The ocean floor remains one of the most mysterious places in the universe.

In fact, “we have better maps of the moon and Mars than we do of our own planet,” Feldman previously told CNN.


Though people have been exploring the ocean’s surface for tens of thousands of years, only about 20% of the seafloor has been mapped, according to 2022 figures from NOAA.

Given high interest in the Mariana Trench, however, researchers have made several efforts to give increasingly detailed pictures of its features. But that’s not easy: Due to the vastness and deepness of the bottommost ocean zone, scientists must rely on sonar, or acoustic, technology to attempt to give a full picture of what’s below.

Because instrumentation and technology are constantly improving, the estimated depth of the Challenger Deep has been updated as recently as 2021 to about 35,876 feet (10,935 meters).

How deep is the ocean? Deeper than the highest point on Earth's surface, by more than a mile

Jessica Orwig
Thu, June 22, 2023 

Shot from an underwater cave looking up to the sun at the water's surface.
Most of the ocean is unexplored terrain.
Inusuke/Getty Images

The ocean is significantly deeper than the highest point on Earth's surface.

The Titanic is farther down than the deepest-diving mammal, the Cuvier's beaked whale, ventures.


Even this wreck doesn't come close to the deepest-crewed mission that reached 35,839 feet in 2019.


This article is primarily transcribed from a 2017 Insider video: "This incredible animation shows how deep the ocean really is." Some of the information has been updated.

Just how deep does the ocean go? If you took the highest point on land and submerged it, you would still have more than a mile between you and the deepest point in the ocean.

The oceans harbor 99% of all living space on Earth and have enough water to fill a bathtub that's 685 miles long on each side. To compare, the state of California is about 720 miles long.

For scale, the average height of a human is about one-sixteenth the typical length of a blue whale — the largest animal on Earth. Blue whales usually hunt at depths of around 330 feet, within the well-lit zone of the ocean.


Blue whales can dive to depths of more than 1,600 feet.
Robert Smits/Getty Images

Deeper down, at 700 feet, the USS Triton became the first submarine to circumnavigate the Earth in 1960.

At 831 feet, we reach the deepest free dive in recorded history by the Austrian-born diver Herbert Nitsch. The pressure is 26 times greater here than at the surface, which would crush most human lungs. But blue whales manage it when they dive to a max depth of 1,640 feet to hunt giant squid.

During his descent, Nitsch developed severe decompression syndrome, which led to multiple brain strokes. However, he reached the surface, recovered inside a hyperbaric chamber, and ultimately survived to tell the tale.

At 2,400 feet, we reach the danger zone for modern nuclear-attack submarines. Any deeper and the submarine's haul would implode.

Reaching 2,722 feet down is where the tip of the world's tallest building, the Burj Khalifa, would reach. A little farther at 3,280 feet, we're deep enough that sunlight can't reach us. We've now entered the midnight zone.

Many animals down here can't see, such as the eyeless shrimp at 7,500 feet which thrive near scalding hot underwater volcanoes.


Underwater volcanoes are a haven for deep-sea life.
Ralph White/Getty Images

At this depth, temperatures are just a few degrees above freezing, but the water around hydrothermal vents can heat up to 800 degrees Fahrenheit.

Around 9,816 feet is the deepest any mammal has been recorded swimming — the record was set by the Cuvier's beaked whale.

But not even Cuvier's beaked whales could explore the wreck of the Titanic, which rests at a staggering depth of 12,500 feet.

The pressure is now 378 times greater than at the surface. Yet you can still find life like the fangtooth hagfish and dumbo octopus, the deepest-living octopus on Earth.

At 20,000 feet is the hadal zone, an area designated for the ocean's deepest trenches, such as the Mariana Trench.


The Challenger Deep is the deepest point on Earth.
blueringmedia/Getty Images

If you tipped Mount Everest into the Mariana Trench, its summit would reach down to 29,029 feet — that still doesn't compare to the two deepest-crewed missions in history.

In 1960, the oceanographer Jacques Piccard and Lt. Don Walsh descended to the lowest point on Earth, the Challenger Deep, at a record 25,979 feet below the surface.

They held the record for decades until the explorer Victor Vescovo came along in 2019. Vescovo made three dives to the Challenger Deep that year and set a new record on the third dive, reaching a depth of 35,839 feet.

Scientists have sent half a dozen unmanned submersibles to explore the Challenger Deep, including Kaiko, which collected more than 350 species on the seafloor from 1995 to 2003. But scientists estimate there are potentially thousands of marine species we have yet to discover.

Humans have explored an estimated 5% to 10% of Earth's oceans. We've only just begun to understand the deep, dark world that flows beneath us.

Watch the original video here:


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