NASA has thrown together four astronauts into an underwater tin can -- well, OK, a habitation module -- sitting on the seafloor a few miles off the Florida Keys for a nine-day stretch beginning this week.
The goal is to test some new equipment and procedures, but experts say the real payoff may be in figuring how people get along under pressure, just like a long-duration flight to Mars or beyond.
The NEEMO project (NASA Extreme Environment Missions Operation) is one of several "space analogs" or trial runs for space here on Earth. Others include installations are in Antarctica, the Arizona desert, Devon Island, Canada; and Mauna Kea, Hawaii.
"For any kind of exploration they are essential," said John Rummel, biology professor at East Carolina University and former NASA senior astrobiologist. "You don't want that someone going into a difficult situation without the ability of the control center to fix anything to happen for the first time on surface of the moon or Mars."
Still, going 69 feet underwater is not like going into space. The buoyancy is different, the water provides resistance, divers are on hand to help the "aquanauts" suit up and accomplish certain tasks when they leave the module. And there are fish swimming around.