Three astronauts, a doctor and two technicians have completed an 18-day stay at the world's only undersea habitat to test remote robotic surgery and Moon-walking techniques.
The ninth of NASA'sExtreme Environment Mission operations
(Neemo) took place at a depth of 18m (60ft) at the Aquarius underwater base which lies three miles off the coast in the Florida Keys National Marine Sanctuary.
The astronauts carried out simulated underwater Moon-walks and explored their surroundings with the help of an ROV, an unmanned subsea vehicle, as they would do on the Moon.
The mission was also designed to give astronauts experience of operating with the two-second communications delay that occurs between the Earth and the Moon.
Doctors thousands of miles away remotely guided the astronauts through medical diagnosis and used virtual reality technology to guide simulated surgery using a prototype next generation surgical robot.
The team also tested human performance and health characteristics related to fatigue and stress.
The design of Aquarius allows 'aquanauts' to live and work on the seafloor for extended periods using a technique called saturation diving, which increases the time divers can spend working deep in the ocean.