In the North Pacific, the underwater slope leading to the Aleutian Trench is believed to be teeming with worms, clams, anemones, and countless microbes thriving on methane seeping from sediment. "People know they're there, but no one has taken a close look," says Lisa Levin, a marine ecologist and biologist at the University of California, San Diego, when discussing deep-sea organisms. One reason for this is that the iconic U.S. research submersible, Alvin, cannot dive deep enough.
Now, Levin is finally going to come face to face with the extraordinary deep-sea ecosystem. According to Science magazine, a $50 million upgrade project will allow the "Alvin" submersible to dive to a depth of 6,500 meters. Levin's mission is to investigate methane leaks off the coast of Alaska, marking the first time the United States will conduct manned research below 4,500 meters, breaking the previous depth limit for submersibles.
This depth limit restricted the "Alvin" to reach only about 68% of the seafloor. But with a thicker titanium hull and stronger seals, the "Alvin" can now reach 99% of the seafloor - roughly equivalent to the combined area of Asia, Africa, Europe, Australia, and North America.
Shana Goffredi, a member of the Alaska expedition team and marine biologist at the Western Academy of the United States, said that greater depths will allow scientists to see new organisms and ecosystems. Previously, Goffredi studied life around shallow methane leaks, such as symbiotic microorganisms that can convert methane into energy - worms. Now, she wants to see what organisms survive in this more extreme environment around 5,000 meters deep near the Aleutian Trench. "This is one of the most exciting things about this expedition."
Jeffrey Marlow, an environmental microbiologist at Boston University in the United States, said that the ability of the "Alvin" to dive to greater depths will make locations like the deep-sea plains more accessible. At depths of up to 6,000 meters, flat, sediment-covered expanses of the seafloor dotted with potato-sized rocks rich in valuable minerals make them prime targets for mining companies. However, little is known about the organisms that may face risks in this area.
Since the 1980s, France, Russia, Japan, and China have built submersibles capable of taking scientists to depths of 6,500 meters. In 2020, China launched the "Striver" submersible, capable of carrying three people to depths of 10,000 meters. Privately owned submarines have also achieved similar feats. In 2012, "Titanic" director James Cameron piloted the narrow single-person "Deepsea Challenger" to the deepest known point on Earth - a depth of 10,898 meters.
The United States is now catching up. The current upgrade was authorized by the main funder of the "Alvin" project, the National Science Foundation of the United States, in 2004. Due to cost overruns and technical difficulties, the plan to replace it with a new $22 million submersible in 2007 fell through. "Let's just say this wasn't our finest moment," said engineer and Hydrospace Group founder Will Kohnen, who worked on the project oversight committee for nearly a decade.
Submarine managers turned to refurbishing existing machines, but progress was slow. Meanwhile, efforts to expand deep-sea research capabilities in the United States suffered another setback in 2014 when the $8 million new robotic ship Nereus exploded while diving to 10,000 meters.
Now, the United States has finally rejoined the deep-diving club. In addition to the reinforced hull, the upgraded "Alvin" also features a more spacious interior and updated cameras to allow scientists to observe better.
However, while the 1% of the ocean that the "Alvin" cannot reach may sound small, it represents nearly half of the total depth of the ocean. To further expand the researchers' scope, U.S. agencies have opted for robots. In the Alaska expedition, the "Alvin" will be accompanied by two new autonomous underwater vehicles (AUVs) capable of reaching the lowest points of the ocean.
Tim Shank, a deep-sea biologist at the Woods Hole Oceanographic Institution in the United States, explained that these new devices were built after the Nereus disaster, with relatively lower replacement costs. Shank said that in addition to the Aleutian Trench, the two AUVs will navigate to the seafloor at night, map the area, and identify the best sites for the "Alvin" to visit during the day. These machines can also conduct their own research, extract sediment cores, take high-resolution photos, and carry ocean chemistry sensors.
