Saturday, November 12, 2022

The Deepest Part of the Ocean Is Practically an Alien Planet

Ashley Stimpson - Yesterday 



How deep is the ocean? At nearly seven miles, the deepest part is a mile longer than Mount Everest is tall.

Both manned and unmanned vessels have reached these depths, called Challenger Deep.
It was long thought nothing could live in the Mariana Trench, but robotic probes have revealed worms, shrimp, and microorganisms.

Almost three-quarters of our world is covered in saltwater, and, on average, the ocean is about 12,100 feet, or 2.3 miles deep. But in certain places, the sea floor plummets to truly astonishing depths.

In the Atlantic Ocean, the Puerto Rico Trench, which lies directly north of its namesake, plunges more than 27,000 feet below the surface. The Indian Ocean’s deepest point is the Java Trench, a 2,000-mile chasm off the coast of Sumatra with depths of around 24,000 feet.

But it’s the Pacific Ocean that boasts the deepest waters on Planet Earth.

How Deep Is the Deepest Part of the Ocean?


About 125 miles east of the Mariana Islands—a U.S. territory north of Guam—lies the deepest place known to man. The Mariana Trench, a crescent-shaped depression on the floor of the Western Pacific, stretches about 1,500 miles long and 43 miles wide.

The Mariana Trench is a subduction zone, the spot where one tectonic plate slides under the other. The Pacific Plate, which makes up half of the trench (the Philippine Plate comprises the other), is made up of some of the oldest seafloor in the world, around 180 million years old, so it has been settling lower and lower for quite some time. Two other factors contribute to the Mariana Trench’s enormous depth. First, its remote location means it’s far from any rivers that might fill it up with sediment. Second, fault lines cut the Pacific Plate into narrow grooves near the Trench, allowing it to fold at a steeper angle than in other subduction zones.

At the southern end of the Mariana Trench, there is a small, narrow valley known as the Challenger Deep. It is named for the 1951 expedition that first recorded its depth—an astounding 36,201 feet, or about 6.8 miles. If Mount Everest were placed into the trench at this point, its peak would still be underwater by more than 1.2 miles.

What’s It Like Down There?

At nearly seven miles underwater, the pressure is around 1,000 times greater than what we experience at sea level. Water temperatures hover around freezing, and everything is shrouded in absolute darkness.

It may be cold and quiet, but the deepest part of the ocean, we’re learning, is a noisy place. In 2015, a team made up of researchers from the National Oceanic and Atmospheric Administration, the U.S. Coast Guard, and Oregon State University, dropped a hydrophone (a waterproof microphone) into the Challenger Deep. Within 23 days, the data capacity of the device was full. After analyzing the recordings, the researchers reported hearing natural phenomena like earthquakes, typhoons, and whale calls, as well as man-made noises like boat engines.

Have Humans Explored the Deepest Part of the Ocean?


In 1875, the HMS Challenger measured the depths of the Challenger Deep using a weighted rope. The discovery, made by a crew circumnavigating the globe on a marine research expedition, was a completely serendipitous one after unpredictable wind blew the ship off its planned course. More than 75 years later, Challenger II surveyed the spot using echo sounding, an easier and much more accurate way to map the ocean floor. This survey confirmed the Challenger Deep as the deepest spot in the world, at more than 36,000 feet below the surface.

Only three divers have ever explored the Challenger Deep. In 1960, Jacques Piccard and U.S. Navy Lieutenant Don Walsh explored the Challenger Deep in a submersible called Trieste. The dive lasted only 20 minutes due to the extreme pressure, and it kicked up so much debris from the seafloor that the men were unable to take photos.

It took more than 50 years for the next adventurer to reach the Challenger Deep. Filmmaker James Cameron visited in 2012 in a submarine he designed himself. During the three-hour dive, immense pressure damaged Cameron’s equipment. Batteries and sonar equipment went dead, and the vessel’s thrusters malfunctioned.

Dozens of other unmanned research vessels have explored the Mariana Trench and the Challenger Deep, contributing to our growing, but still incomplete knowledge, about the deepest corner of our world.

What Lives Down There?



One of at least 15 species of dumbo octopus, found at depths of at least 13,000 feet, uses its ear-like fins to swim. Dwelling in the Midnight Zone, they are the deepest-living octopuses ever found.© NOAA Ocean Explorer

Pressure at the bottom of the Challenger Deep is so great that calcium cannot exist except in solution, meaning that bones would theoretically dissolve at such depths. Because of this, scientists are skeptical that any fish or other vertebrate could survive there. However, robotic probes that have sampled the water and seabed of the Challenger Deep have returned worms, shrimp, and microorganisms.

Paradoxically, there are only trace amounts of life on the floor of the Challenger Deep, yet scientists believe life on Earth may have gotten its start in these depths. Deep, hydrothermal vents that spew mineral-rich seawater—like the ones found in the Mariana Trench—may have provided the ideal conditions for the origin of life on our planet. The chemical reactions facilitated by these vents could be responsible for the increasingly complex organic compounds that eventually evolved into the lifeforms familiar to us today.


Terrifying Images Show Monstrous Deep-Sea Creature With Enormous Fangs

A fangtooth fish spotted at a depth of 800 meters (around 2,600 feet) below the surface. Relative to body size, the teeth of this species are larger than any other marine species. NOAA Ocean Exploration

Deep in the ocean lives a ghoulish fish with huge and menacing, fang-like teeth.
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The aptly named common fangtooth fish (Anoplogaster cornuta)—sometimes referred to by its nickname "ogrefish"—inhabits deep waters all around the world, occurring at depths between 650 and 6,500 feet, although the species has been observed as far down as 16,000 feet. This makes it one of the deepest-living fish.

While the fangtooth fish sometimes rise near to the surface at night to feed, they generally spend their time in waters deeper than 3,300 feet in the open ocean away from land, according to Tracey Sutton, a professor with the Guy Harvey Oceanographic Center at Nova Southeastern University in Florida.

"The one species is truly a child of the Earth, occurring in all but the polar seas," Sutton told Newsweek.

The common fangtooth fish is rarely seen by humans—the Monterey Bay Aquarium Research Institute in California, for example, has spotted the creature fewer than 10 times in around 30 years of conducting deep-sea expeditions with remotely operated vehicles. However, this does not necessarily mean that the fish is truly rare.

"It occupies nearly all of the global deep ocean, so its total numbers could actually be staggeringly high—though it is a loner, not occurring in groups, and thus not abundant in any specific place," Sutton said.

While there is only one confirmed species in its family, a second was described from a juvenile specimen but never collected as an adult, according to Sutton. Fangtooth fish have no known close relatives.

Despite its small size—the common fangtooth fish reaches lengths of around 6 to 7 inches—the characteristic features of this species are the "huge" head and teeth relative to the rest of its body.

The mouth of this fish is full of long, pointed teeth—including two sets of large fangs on the lower and upper jaw—which enable it to catch and hang on to prey of many different sizes, a beneficial adaptation in the deep sea where food can be hard to come by.

Common fangtooths tend to be more active than many other deep-sea fishes and will seek out food by heading toward the surface at night—rather than lying around and waiting for prey like other ambush predators, who might using various luring techniques.

The diet of the common fangtooth includes other fish, crustaceans and cephalopods—the group of animals that contains octopuses, squid and cuttlefish.

When a fangtooth approaches prey animal, the fish opens its huge mouth and sucks the unfortunate victim inside.

"They are voracious—they seem to eat anything that will fit in their mouths," Sutton said.


A composite image showing two fangtooth fish. These animals grow to around seven inches in length.
ʩ 2022 DEEPEND-RESTORE/Dant̩ Fenolio

The teeth of this species, relative to body size, are larger than any other marine species, according to the Smithsonian Institution. They are so big, in fact, that the fish has special pouches on the roof of its mouth to accommodate the fangs on the lower jaw when the mouth is closed.

This species has relatively poor eyesight but to compensate for this, as well as the low light conditions in the water where it lives, the fangtooth has an unusually prominent lateral line—a sensory system found in fish and aquatic amphibians—that helps it to sense movement and vibrations in the surrounding water.


A close-up on the face of a fangtooth fish. These animals live in deep sea waters around the world. 


"It has a complex arrangement of nerves on its head. In a manner of speaking, it 'listens' with its face," Sutton said.

This arrangement of nerves is the "front end" of the lateral line system, according to Sutton. It explains the heavy "sculpting" on the front of the fangtooth's face, which you can see in the image above.

The common fangtooth is dark brown to black in color, which helps the fish to camouflage itself in the deep ocean—helpful for catching prey or avoiding predators. Its body is also covered in prickly scales and spines.


A juvenile fangtooth fish displaying its typical coloration. While adult fangtooths tend to be uniformly black or dark brown in color and have enormous fangs, the juveniles are usually light gray and feature smaller teeth. 
© 2022 DEEPEND-RESTORE/Danté Fenolio

Because they live so far down, scientists know little about their life and reproduction habits, but the fangtooth fish reproduce via external fertilization—a process in which females lay a clutch of eggs as the males release sperm into the water to fertilize them.

The fish do not have many predators, but animals that do hunt them include tuna and marlin. While fangtooth fish live far away from human civilization, they still face several man-made threats.

For example, deep-sea mining activities and fossil fuel exploration can cause "catastrophic" damage to deepwater ecosystems—as occurred after the Deepwater Horizon oil spill in the Gulf of Mexico—according to Sutton.

"Fisheries are also expanding into deep pelagic (being neither close to the bottom nor near the shore) waters as coastal fisheries are depleted," Sutton said. "Last, climate change is predicted to change ocean circulation, which is predicted to reduce the amount of pelagic life."

The fangtooth fish is one of millions of species thought to be living in the deep ocean, most of which have never been seen or described by humans. Among these weird and wonderful deep-ocean creatures are the vampire squiddumbo octopuses and the bloody-belly comb jelly.

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