The 14th expedition of NASA Extreme Environment Mission Operations, or NEEMO, plans to return to the surface Sunday after spending two weeks undersea aboard the Aquarius Underwater Laboratory near Key Largo, Fla. 

At more than 62 feet (19 meters) deep below the ocean's surface, crewmembers are performing a series of activities inside and outside Aquarius that simulates an environment such as that of the Earth's moon or an asteroid. Among the experiments are employing near-scale mockup vehicles, imitating "spacewalks" and using mannequins during crew rescue testing. 

Canadian Space Agency astronaut, Chris Hadfield, leads the NEEMO 14 expedition that began May 10. Hadfield, from the seafloor in a media teleconference Friday, said he is pleasantly surprised at the realism between the undersea and space.  

"With the water you can simulate being on Mars, being on the moon, or even being on an asteroid," he said. 

The undersea world parallels space in many ways because of its forced physiological and psychological separation.  

Aquarius is pressurized at the level slightly higher than the pressure in car tires. By wearing diving gear and weighted backpacks, the NEEMO 14 crew is able to simulate low gravity that allows it to practice extravehicular activities (EVAs), simulating activities that astronauts would be likely to perform during missions in space. The vehicles that are used during the dives are similar to landers and rovers being developed by NASA.  

Hadfield is joined by five other members in the undersea mission: Flight surgeon Thomas Marshburn, Lunar Electric Rover Deputy Project Manager Andrew Abercromby, research scientist Steve Chappell and habitation technicians Nate Bender and James Talacek of the University of North Carolina at Wilmington.  

One of the tasks this week was establishing a 20-minute communication delay with Mission Control, representative of the time it takes to send a message from Mars, in order to increase levels of isolation and test the crew's ability to work independently. 

Additionally, thousands of data points have been collected to help NASA design spacesuits that would be durable for long-term space missions, have higher levels of protection against malfunctions and work in different levels of gravity. 

"But how do you control where you are if you can't regularly grab on to manmade handholds or places to click in your feet?" Hadfield asked. "So we do some developmental work without gravity, some we weigh ourselves down so that we're simulating the surface of the moon or one of Mars' moons with very small gravity, or Mars itself, which  has a little over one-third Earth's gravity." 

Hadfield said more than 50 simulated spacewalks will have been performed before the mission ends. This includes exploring reefs with limited tools--the simulation there being that there are tens of thousands of asteroids that go by the Earth over time and that are in different orbits around the Sun---to help develop methods of navigation, delayed communication and traverse planning. 

"We're finding that sometimes a center of gravity that is completely wrong on Earth that would just give you a backache in a matter of minutes becomes better and in fact may help you with some of the tasks when you feel so much lighter," Hadfield said. 

Behavioral health and performance experiments comprise another major part of the mission. Bodily fluid measurements, reaction times and sleep patterns are some of the data crewmembers are studying to assess what stimulations provide a healthy threshold in extreme environments. 

Hadfield acknowledged that the road to exploring the rest of the universe is difficult and people have taken huge risks to create the exploration and discoveries that are possible now.   

"We are just now at the point of starting to permanently leave our planet," Hadfield said. "It's easy to not even see that it is happening."