Posted on behalf of Brian Owens.
After a two-year, US$41-million upgrade, the venerable Alvin submersible is about to return to sea.
On 25 May, the research ship Atlantis will leave the Woods Hole Oceanographic Institution (WHOI) in Massachusetts with Alvin on board, bound for Astoria, Oregon. After a series of US Navy certification cruises in September and a scientific-verification cruise in November, Alvin will return to full service in December studying the deep ocean off the US Pacific Northwest.
The main improvement in this first phase of the Alvin upgrade is the new titanium sphere where the sub’s three-person crew sits (see Nature’s feature story ‘Deep-sea research: Dive master‘). It is 18% bigger than the previous sphere and has two extra windows and high-definition cameras, giving the scientists a better view of the deep ocean. It also has more comfortable seats. In addition, the manipulator arms have longer reach, and the sample-collection basket can carry twice as much weight — up to 181 kilograms.
Even though the new sphere was designed to travel to depths of 6,500 metres, Alvin will still be limited to its old depth of 4,500 metres after the first phase of the upgrade. Holding it back from greater depths are battery limitations, says Susan Humphries, who is in charge of the upgrade programme at WHOI. Alvin uses lead–acid batteries, which do not provide enough power for longer, deeper dives. Lithium-ion batteries would be better, but are considered to have too great a risk of fire for now. “In a few years, once the battery technology has matured, we’ll complete phase two,” says Humphries. She hopes that within five years, when Alvin is scheduled for regular maintenance, the problem will be solved.
In the meantime, ocean scientists are eager to get back below the waves. Over its five-decade career, Alvin has been responsible for revealing some of the deep ocean’s biggest surprises, including the famous ecosystems powered by hydrothermal vents rather than sunlight. Julie Huber, a microbiologist at the Marine Biological Laboratory, also in Woods Hole, has been on three Alvin dives in the past. She is looking forward to the new exploration opportunities, but sounds a note of caution: “I want to wait for them to have 50 safe dives under their belt before I go back.”
Disclosure: Brian Owens is in Woods Hole as part of the Logan Science Journalism Fellowship at the Marine Biological Laboratory.