Alvin dives to new depths

With the completion of the new Alvin, the Woods Hole Oceanographic Institute’s storied deep-sea submersible, 50 million square miles of previously inaccessible seafloor real estate is now open to scientific investigation. Before its upgrades, Alvin was rated to dive to 15,000 feet, but a new titanium personnel sphere means it can now dive as deep as 21,000 feet—and that depth rating opens up 98 percent of the seafloor to Alvin’s robotic fingertips.

For the first time, scientists will be able to experience and sample vast realms of the unseen from inside an American submersible. We don’t know what we’ll find with the re-vamped Alvin—that’s the point of science, after all—but with a substantial fraction of the seafloor newly accessible, the possibilities are alluring. This month, Alvin will be exploring the East Pacific Rise hydrothermal vent field, studying the growth rates of massive, tentacle-like Riftia tube worms.

But those hydrothermal vents—where scalding fluids with abundant electron-rich iron, manganese, and sulfur chemicals create chimney-like “black smokers”—are just one of three distinct flavors of seafloor chemotrophy, oases of life driven by the chemicals streaming out of the seafloor. Methane seeps are less flashy, but the bizarre microbial partnership that metabolizes methane and supports the food pyramid of clams, mussels, crabs, and fish represents a key control point for climate. And most recently, a new class of chemosynthetic system was found in the North Atlantic at Lost City, where destabilizing mantle minerals generate carbon-rich emissions that lead to towering formations of carbonate rocks.

With Alvin’s improved depth rating, scientists may be well on their way to identifying even more geochemically unique underwater worlds. (The current depth rating remains 15,000 feet, but as improved power sources are incorporated over the next couple of years, the 21,000-foot benchmark will be within reach.) And the array and connectivity of the sub’s new instruments will help researchers investigate when they do. Nimbler arms allow Alvin pilots to deposit sensors or collect specific pebbles with improved dexterity. Electronic re-wiring gives users the option of including their own instruments, turning the sub into a more customizable roving laboratory.

On one of the new Alvin’s first dives, a brand new sensor—plugged into the sub the night before—made some of the most detailed in situ pH measurements to date of seafloor methane seeps. The integrated result is a functionally enhanced sub that makes the underwater realm easier to access than ever before—and each new investigation of these unseen worlds can dramatically change the way we view life in the universe. By uncovering new forms of chemotrophic life surrounding other types of seafloor venting—a very real possibility given how little of the seafloor we have studied—our library of biological possibility may well expand once more.