Sarah Bedolfe
Getting to the ocean’s deepest point, Challenger Deep, 7mi below the surface

Focusing on science, technology, engineering, and math, as they pertain to the ocean.

The ocean is still a big mystery to science – only a small portion of it has been explored.

The deepest point in the ocean at 10,994 meters (6.8 miles) below the surface, is the Mariana Trench near Guam. Known as Challenger Deep, this spot has only been visited once, by two men in 1960. Now, more than fifty years later, several groups are striving to return, and ocean explorer and filmmaker James Cameron is poised to do it first.

The DEEPSEA CHALLENGER is lowered into the Sydney Harbor in Australia. Photo Courtesy Brook Rushton, DEEPSEA CHALLENGE.

The deep sea is dangerous to humans for obvious reasons: there is no air, it is completely dark and extremely cold. But the biggest challenge is pressure – the deeper you go, the more pressure is pushing down from above, and the vehicle must be strong enough to protect the people inside. To put the pressure in perspective, a member of Cameron’s Deepsea Challenge team, Patricia Fryer said, “It would be about the equivalent of turning the Eiffel Tower upside down and resting it on your big toe.” 

The submersible used in 1960 was a bathyscaphe (from Greek bathys, or deep, and skaphos, or vessel), named the Trieste. It consisted of a tiny cabin for two crewmembers, Jacques Piccard and Don Walsh, suspended under an enormous flotation tank.

Photo by US Navy via Wikimedia Commons, Public Domain

The cabin was about 7 feet (2m) cross, had just one small window, and maintained the crew’s oxygen supply with rebreather technology. It was made of steel 5 inches (12.7 cm) thick, and was spherical, which is the strongest shape; 16,000 pounds of pressure would be pushing down on every square inch of the cabin when they reached the bottom of the ocean.

Photo by US Navy via Wikimedia Commons, Public Domain

The bathyscaphe’s flotation tank was necessary because the cabin would be too heavy otherwise to return to the surface. It was filled with gasoline, which is lighter than water and does not compress, or shrink, under pressure. Heavy weights were attached to let them sink. It took almost five hours to reach Challenger Deep, where Walsh and Piccard stayed for only 20 minutes. The weights were dropped to allow the Trieste to float back to the surface.

Cameron’s sub, the Deepsea Challenger, is extremely high tech, but it uses some of the same devices as the bathyscaphe: a large flotation device, a small sphere made of thick steel with a tiny window, and removable weights to travel to the seafloor and back.

The Deepsea Challenger, however, is much more streamlined than the Trieste so it can sink and rise rapidly, and spend much more time on the seafloor. It also has movable arms for collecting samples, and high quality 3D cameras for capturing the entire trip on film. Because the window is so small, the pilot will also depend on cameras to see outside.

Another major difference is that Cameron’s sub seats one, and will set the record for world’s deepest solo dive, which he set just last week, when he took the Deepsea Challenger on a test dive to just over 5 miles (8,166m) deep near Papua New Guinea. 

The story of Cameron’s trip to the bottom is still unfolding so stay tuned!



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