Outside Aquarius earlier this year. The undersea lab is serving as a habitat for a NASA analog mission to an asteroid. Photo Credit/NASA/Facebook

Four U.S., European and Japanese astronauts will evaluate a range of asteroid exploration strategies, following their descent on Monday to NOAA’s Aquarius Reef Base under sea habitat off Key Largo,Fla., for a 12-day stay.

Astronaut Dottie Metcalf-Lindenburger, a NASA shuttle veteran, leads a crew that includes European Space Agency astronaut Timothy Peake, Japan Aerospace Exploration Agency astronaut Kimiya Yui and Cornell University astronomer Steve Squyres.

During their undersea stay, the aquanauts will deal with simulated communication delays associated with deep space travel, evaluate spacewalk tools as well as surface translation and scientific sample gathering techniques. Medical experts will assess their effectiveness and interpersonal behavior as well as their responses to simulated medical emergencies.

“The reason we are doing this is we want to learn before we go out into space,” explained Metcalf-Lindenburger.

NASA astronaut Dottie Metcalf-Lindenburger leads undersea asteroid mission simulation. Photo Credit/NASA photo

Her crew is participating in a long running NASA exercise known as NASA Extreme Environment Mission Operations. The exercise involves an analog mission to a destination NASA may one day explore with actual astronauts.

Two years ago, President Obama directed the space agency to plan for a human mission to an asteroid by 2025. The mission would serve as a learning experience or stepping stone to a Mars mission a decade or so later.

A NASA web site offers the opportunity to follow the current mission with NASA updates as well as on Facebook and Twitter. Several educational events are planned.

The latest of NASA’s 16 NEEMO mission will take off where an abbreviated mission to Aquarius last October was cut to just six days by Hurricane Rina. Squyres, who also chairs the independent NASA Advisory Council and serves as the principal investigator for the Mars Exploration Rover project, is the only hold over from the previous exercise.

The 16th NEEMO expedition will carry out spacewalks in coordination with small submersibles outside Aquarius, which is anchored 62 feet below the Atlantic Ocean, 3.5 miles east of Key Largo.

During the early portion of their under water stay, the aquanauts will move around the sea floor while using tethers to anchor them. The buoyancy of the water will simulate the absence of gravity on a real asteroid.

As the mission progresses, they will compare their experiences with the tethers to surface explorations using submersibles vehicles to hover over sites of scientific significance. The submersibles will stand in for Multi Mission Exploration Vehicle prototypes NASA has been testing for use on planetary surfaces like the moon or Mars as well as an asteroid.

Asteroids present unique challenges, including low gravity and erratic spin rates as well as unpredictable lighting conditions and lengthy communications delays with Earth-based flight control teams. Scientists believe asteroid exploration will reveal more about the evolution of the solar system; yield resources, including water and rare metals of use to deep space explorers; and assist in the development of strategies to prevent potentially catestrophic impacts between near-Earth objects and the Earth.