We’ve heard a lot recently about the Russian space station Mir and the new International Space Station. But most people don’t know about a third station designed to allow humans to live and work in a hostile environment–not space, but the sea.

It’s called Aquarius, and recently a team of six “aquanauts” completed an eight-day mission to it, one of more than 20 that have been carried out in the past five years.

Aquarius, built in the mid-1980s, is owned by the National Oceanic and Atmospheric Administration and operated by the National Undersea Research Center through the University of North Carolina at Wilmington. Since 1993, it has been anchored at Conch Reef in the Floriday Keys National Marine Sanctuary, about eight kilometres offshore and 18 metres underwater.

Aquarius, roughly the size of a mobile home, looks, in one reporter’s words, like a cross between a deep-sea drilling rig and the Beatles’ yellow submarine. It’s essentially a large pressurized tank fitted out with all the comforts of home: six bunks, a kitchen, a bathroom, and a laboratory/office/communications area.

A surface buoy contains the compressors and generators that provide air and power, and links Aquarius to ground control on shore and, through the Internet, the entire planet.

Aquarius solves a problem faced by scuba divers: the deeper they go and the longer they stay, the more nitrogen is forced into their blood and tissues from the pressurized air they breathe, and the more slowly they have to ascend to give that nitrogen time to escape. (If they ascend too quickly, the nitrogen forms bubbles, leading to the painful and sometimes fatal “bends.”)

This severely restricts the amount of time divers can stay under. A surface-based diver, for instance, could only stay at Aquarius’s 18-metre depth for an hour.

But U.S. Navy research in the late ’50s and early ’60s showed that if a diver stayed at a given depth for approximately 24 hours, his tissues became completely saturated with nitrogen; after that, no matter how long he stayed down, the decompression time required to return to the surface remained the same.

By living in the pressurized Aquarius, aquanauts soon become saturated and remain saturated. Since they don’t have to worry about returning to the surface, they can work outside for up to nine hours at a time. (Aquarius’s pressurized atmosphere has another benefit: it keeps the water out, so exiting and entering is by way of a simple hole in the floor.)

At the conclusion of a mission, Aquarius is sealed. Over 17 hours the pressure is slowly lowered to sea-level normal; then the aquanauts exit through an airlock and simply swim to the surface.

Aquanauts live under pressure in more ways than one. Not only are there six of them crammed into small quarters, but the pressure interferes with taste and smell. “Food is just something you have to eat,” says one aquanaut. “It’s not a pleasurable experience.” They have be able to deal with emergencies on their own; they can’t simply pop to the surface for help. If they did, they would only have minutes to race eight kilometres to shore to reach a decompression chamber.

Like astronauts, though, the aquanauts are generally too busy to worry about possible danger. They spend hours outside every day conducting research on the nearby coral reef that would be impossible from the surface.

Coral, a living organism, provides a home for other sea life. It’s vital to the health of many fisheries and protects beaches from erosion.

But world-wide, coral reefs are suffering from potentially fatal bleaching. The August mission to Aquarius wanted to find out how deep the reef’s bleaching extends. The aquanauts also tagged fish to study their migration patterns.

Previous Aquarius missions have proven that increased ultraviolet radiation is damaging coral reefs; studied the impact of sewage; investigated coral’s and sponges’ chemical defenses against predators (which are now being investigated by pharmacological companies); explored underwater vision in fish and examined fossil coral to see how the reef has changed over time.

All this costs just $1.2 million a year. “One space shuttle mission is enough to run our program for 500 years,” says Steven Miller, associate director of the National Undersea Research Center. He feels far too little ocean research is being done, especially considering the ocean is vital to life on Earth.

If he had his way, the new millennium really would be the “Age of Aquarius.”

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