NASA evacuated a crew of astronauts Wednesday from an underwater lab off the coast of Florida where they were training for a trip to an asteroid, due to the approach of Hurricane Rina.
The NASA Extreme Environment Mission Operations team ended practice drills after five days of what was supposed to be a 13-day mission, the US space agency said.
"Despite the length, we accomplished a significant amount of research," said NEEMO Project Manager Bill Todd.
"We're already learning lessons from working in this environment."
NASA announced earlier that the crew was heading back to the surface.
"Hurricane Rina just a little too close for comfort," the US space agency said in a message on the microblogging site Twitter.
The crew includes Japanese astronaut Takuya Onishi, Canadian Space Agency astronaut David Saint-Jacques, commander Shannon Walker of NASA, and Steve Squyres, an expert on planetary exploration at Cornell University in New York.
They were almost midway through their mission at the Aquarius Underwater Laboratory, the only undersea lab of its kind in the world located three miles (4.5 kilometers) off the coast of Key Largo, Florida.
The practice run aimed to help astronauts figure out how they would get around on a near gravity-free asteroid, a trip President Barack Obama has said could happen by 2025.
The crew performed "six underwater spacewalks and one day of scientific research inside the Aquarius habitat," NASA said.
Hurricane Rina, packing winds of 110 miles (175 kilometers) per hour, is a category two storm that is expected to make landfall near the sprawling resort city of Cancun on Thursday.
The next NEEMO mission is tentatively set for the summer of 2012, NASA said.
Explore further: Astronauts dive deep in practice for asteroid visit