Journey to the Deep

Outside the submersible, the water was blacker than black. Pilot Victor Vescovo had been sinking deeper and deeper into the Pacific Ocean for four hours. His destination: a narrow underwater depression called the Mariana Trench.

The descent was quiet. Then all of a sudden, the sub gently touched the ocean floor, sending up a cloud of fine sand. “At bottom! Repeat, at bottom!” Vescovo announced into a microphone. On a ship at the surface, his team erupted in cheers. At more than 10,920 meters (35,827 feet) underwater, Vescovo had reached the deepest known point on the planet.

The dive was part of the Five Deeps Expedition. That mission explored the deepest spots in each of Earth’s five oceans (see Deep Dives). Along the way, researchers discovered new landforms and organisms. “We are getting to do true exploration to places no one has ever been to before,” says Vescovo, who led the expedition. 

Victor Vescovo was driving an underwater vehicle. The water was blacker than black outside. He had been sinking for four hours. His submersible was going deeper and deeper. It dove into the Pacific Ocean. He was headed for a long underwater valley. It’s called the Mariana Trench.

The sub drifted down quietly. Then it hit the ocean floor all of a sudden. It sent up a cloud of fine sand. “At bottom! Repeat, at bottom!” Vescovo said into a microphone. His team was on a ship at the surface. They began to cheer. Vescovo was more than 10,920 meters (35,827 feet) underwater. He had reached the deepest known point on the planet.

The dive was part of the Five Deeps Expedition. The mission visited Earth’s five oceans. It explored the deepest spots in each one (see Deep Dives). Its scientists found new landforms and creatures along the way. Vescovo led the expedition. “We are getting to do true exploration to places no one has ever been to before,” he says. 

Trenches are the deepest spots on Earth. They typically form at the boundaries between tectonic plates. When one plate slides under another, a deep, long depression can form in the ocean floor. “The dramatic landscape of the seafloor is breathtaking,” says geologist Heather Stewart. 

To visit the trenches, Vescovo needed a special underwater vehicle. He worked with engineers to design an SUV-sized sub, named the Limiting Factor, with sturdy metal walls 9 centimeters (3.5 inches) thick. Its design allows it to withstand the enormous pressure of water pushing down at the bottom of a trench. “It’s like being squished under 150 fully loaded jumbo jets,” says sub designer John Ramsay.

Trenches are the deepest spots on Earth. They usually form along the edges of tectonic plates. One plate can slide under another. That can create a deep channel in the ocean floor. “The dramatic landscape of the seafloor is breathtaking,” says Heather Stewart. She’s a geologist.

Vescovo needed a special underwater vehicle to visit the trenches. He worked with engineers to design an SUV-sized sub. It was named the Limiting Factor. It had strong metal walls. They were 9 centimeters (3.5 inches) thick. The weight of the water above would push down on the sub. Its design allowed it to withstand this huge pressure. “It’s like being squished under 150 fully loaded jumbo jets,” says John Ramsay. He helped create the sub.

Over 11 months, Vescovo and a team of 10 scientists and engineers sailed more than 74,000 kilometers (46,000 miles) across the world’s oceans. Before each dive, the team used an instrument called sonar to scan the seafloor. Sonar sends out sound waves and measures how long the vibrations take to bounce off surfaces. That allowed the researchers to locate the deepest part of each trench. 

Then the team used a crane to lower the sub into the ocean, and Vescovo began an hours-long descent. The real fun started when he finally reached the seafloor. “I just went exploring!” he says. “I drove around looking for interesting things and creatures.”

Vescovo traveled with a team of 10 scientists and engineers. The mission took more than 11 months. The trip took them more than 74,000 kilometers (46,000 miles) across the world’s oceans. The team used sonar before each dive. The instrument scanned the seafloor. The device sent out sound waves. They bounced off surfaces. The sonar measured how long the waves took to return. That allowed the scientists to find the deepest part of each trench. 

Then the team used a crane. It lowered the sub into the ocean. Vescovo began an hours-long dive. The real fun started when he finally reached the seafloor. “I just went exploring!” he says. “I drove around looking for interesting things and creatures.”

The team also dropped three box-shaped devices, called landers, into the water. The landers sank to the seafloor, where they took photos and collected water samples. They were also equipped with a special tube stuffed with bait. Any animal that entered the tube became trapped. At the end of each dive, the sub and the landers unloaded weights and floated to the surface.

The deepest dives lasted 12 hours. Each dive led to new observations and discoveries. At the bottom of the Mariana Trench, the team spotted a type of eel with a see-through head!

The team also dropped three landers into the water. They’re box-shaped devices. The landers sank to the seafloor. There, they took photos. And they collected water samples. The landers also had a special tube. It was filled with bait. Any animal that entered the tube was trapped. The sub and the landers had weights. They released the weights at the end of each dive. That allowed them to float back to the surface. 

The deepest dives lasted 12 hours. Each dive led to new discoveries. For instance, the team made a discovery at the bottom of the Mariana Trench. It was an eel with a see-through head!