In this submersible, two people can descend to 11,000 meters and gather samples with a robotic arm.

THE FIVE DEEPS EXPEDITION

‘Five Deeps’ mission to explore mysterious ocean trenches

He scaled Mount Everest and the highest peaks on the six other continents. He skied to the North and South poles. Now, Victor Vescovo, the multimillionaire co-founder of a private equity company in Dallas, Texas, wants to be the first person to visit the deepest point in each of the five oceans. This week, Vescovo was set to complete the first dive in the yearlong Five Deeps Expedition, piloting a titanium-alloy, 12.5-ton submersible down 8408 meters to the deepest part of the Atlantic Ocean, in the Puerto Rico Trench.

Five Deeps may look like a vanity project, but for scientists, it is a rare opportunity to study inaccessible, mysterious places. "If there wasn't this rich guy, there is not any funding agency that would be willing to spend so much money to visit all those areas," says Ann Vanreusel, a deep-sea biologist at Ghent University in Belgium. The expedition will yield high-resolution maps that could offer clues about how ocean trenches form when tectonic plates plunge into the mantle. The dives are also sure to spot new species, which will give researchers a chance to compare the ecosystems that have evolved in these isolated, exotic habitats. "Great insights could come when we can start comparing these ultradeep sites," says Stuart Piertney, an evolutionary biologist at the University of Aberdeen in the United Kingdom.

The HMS Challenger Expedition, a pioneering voyage in the 1870s, showed that life exists across the deep ocean by trawling and dredging up creatures from as deep as 8000 meters. Since then, research trawls have netted cutthroat eels, snailfish, and other animals adapted to the cold and pressure. Some rely on bioluminescence to attract mates or prey in the darkness. Below 8000 meters, sea cucumbers and giant crustaceans called amphipods dominate.

Firsthand exploration of the trenches has been limited. People have reached the bottom of the Mariana Trench, the world's deepest trench, only twice: in 1960, in the bathyscaphe Trieste, and in 2012, when movie director James Cameron descended in an $8 million custom submersible. In 1964, a French submersible descended 8385 meters to what was then thought to be the deepest part of the Puerto Rico Trench. The other three deeps have never been visited, although trenches elsewhere have been probed with remotely operated submersibles and autonomous landers. Landers can make measurements, record images, and collect samples before returning to the surface, but can't be controlled or targeted.

Alan Jamieson, a marine ecologist at Newcastle University in the United Kingdom who designed some of these landers, now can visit multiple trenches himself, as the science leader for the Five Deeps Expedition. In March 2017, he received a cryptic phone call from Triton Submarines, a high-end manufacturer in Sebastian, Florida. After signing a nondisclosure agreement, Jamieson learned that Vescovo had bought a 68-meter-long research vessel from the U.S. government and commissioned Triton to build a submersible capable of diving to 11,000 meters. Designed for quick descents and ascents, the Limiting Factor has three acrylic portholes, leather seats for Vescovo and a passenger, and custom lithium batteries to power propellers for scooting along the sea floor. "When someone phones up and says, ‘We have a multi-multi-multi-million-dollar submarine that can do things that your own gear can't,’ it seems like a logical step forward," Jamieson says.

A rotating cast of 15 collaborators will join Jamieson on the mother ship, Pressure Drop. It has space for three scientists, a wet lab, and a $1.5 million multibeam sonar to map the sea floor and verify its deepest spots.

Race to the bottoms

The Five Deeps Expedition aims to reach every ocean’s deepest trench and seven other deep sites in 11 months.

Atlantic Ocean SouthernOcean Indian Ocean Pacific Ocean Arctic Ocean 8408 m 8183 m 7290 m 10,925 m Mt. Everest8848 m Expedition route 5573 m South Sandwich Trench Java Trench Mariana Trench Molloy Deep Puerto Rico Trench Deep dive 1 Deep dive 2 Deep dive 3 Deep dive 4 Deep dive 5
(MAP) A. CUADRA/SCIENCE; (DATA) FIVE DEEPS EXHIBITION

Once a dive site is chosen, Vescovo will plunge in the sub, following three landers dropped several kilometers apart. The landers, which contain cameras and baited traps, collect water and sediment samples. They also emit acoustic beacons for the sub to follow on its seafloor traverses. Along the way, it will record video with four wide-angle, low-light cameras. Floodlights will help the crew collect rocks or slow-moving organisms with a manipulator arm.

The sub can spend about a dozen hours at the bottom per dive, but the ship will linger only a few days at most sites. Even a cursory look could open windows on trench ecosystems. Examining specimens could reveal their adaptations, and genetic analysis back in Newcastle should yield evolutionary relationships of organisms from various trenches. Jamieson wants to know how species are influenced by temperature, depth, or the downward-drifting supply of food. He also wants to understand why fish in trenches seem to live shorter lives than those on the 6000-meter-deep abyssal plains. Jamieson thinks landslides and rockfalls in the steep-sided trenches may be taking a toll.

The new high-resolution maps could also yield insights into how tectonic forces created the deepest parts of the trenches—revealing cliffs created by faults, for example—says Heather Stewart, a geologist with the British Geological Survey in Edinburgh, who will be visiting at least the first two trenches. Sampled minerals could provide estimates of the water that subducting tectonic plates take into the mantle. These water-bearing minerals weaken the plates, perhaps reducing their potential for shallow earthquakes, and they also drive a deep water cycle in which water is swept into Earth's interior and returned to the surface in volcanic eruptions. Rocks collected from known locations should be more informative than those hauled up randomly in a trawl, says Lara Kalnins, a marine geophysicist at the University of Edinburgh. "They can take images and videos—all of this is context you ordinarily don't get."

After the team leaves Puerto Rico this week, it will head for the South Sandwich Trench, in the Southern Ocean near Antarctica. Then comes the Indian Ocean and the Pacific, and finally the Arctic. For the final leg of the expedition, in September 2019, Pressure Drop will sail up the Thames River to London, and Vescovo and Jamieson will give a lecture at the Royal Geographical Society. Then Vescovo hopes to sell Pressure Drop, the sub, and the landers, slightly used, for $48.2 million.