NASA

Crew members for the current NASA Extreme Environment Mission Operations simulation, or NEEMO, float around a porthole 63 feet below the Atlantic Ocean's surface at the Aquarius Reef Base undersea research habitat. The crew is led by NASA astronaut Dottie Metcalf-Lindenburger and also includes Japan's Kimiya Yui, the European Space Agency's Timothy Peake and Cornell astronomer Steven Squyres. Aquarius team member James Talacek peers out from the porthole.

If NASA’s underwater practice session is any indication of what a real space mission to an asteroid will be like, you can expect to follow along with the exploration of a near-Earth asteroid via Facebook, Twitter and the Web — or whatever takes their place by the year 2025. There’s a string of chats and webcasts that let you in on the action at the Aquarius deep-sea habitat during the simulated mission, known as NEEMO 16.

As the "16" suggests, the space agency has been doing NEEMO — NASA Extreme Environment Mission Operations — for more than a decade. The idea is to simulate the logistics associated with an extended space mission, as well as the isolation, by sending an astronaut crew into the Aquarius, 63 feet (19 meters) below the Atlantic Ocean's surface in the Florida Keys, and have them practice the routines they'd be doing in scuba gear.

This summer's 12-day simulation began on Monday with the four-person crew's "splashdown" into the sea. The NEEMO 16 crew is headed by NASA astronaut Dottie Metcalf-Lindenburger, who flew into space on the shuttle Discovery in 2010, and also includes Japanese astronaut Kimiya Yui, British astronaut Timothy Peake and Cornell astronomer Steve Squyres (who's the top scientist on the Mars rover team, the chairman of the NASA Advisory Council, and a veteran of NEEMO 15). Aquarius habitat technicians Justin Brown and James Talacek play support roles underwater.

Last year marked the first time that the NEEMO exercise was designed in line with the space agency's current plan to send a crew to a near-Earth asteroid by 2025. This year, the four-person crew will bring even more of a sense of realism to the simulation: For instance, they're communicating with an onshore Mission Control team on a delayed basis, to reflect the light travel times that would be involved with a deep-space mission.

They're also experimenting with different ways to explore an asteroid-style surface. Because a small asteroid has nearly negligible gravity, astronauts won't be able to tramp across it as if it were Earth or even the moon. One option would be to use attachment points and handholds to move across the asteroid surface. Another option would be to use mini-spacecraft to hover over and touch down on the surface. Both techniques are being tested during NEEMO 16.

During the latter part of the simulation, Nuytco's DeepWorker one-person submersibles will be deployed for underwater excursions by the NEEMO aquanauts. "They get flown around the reef with their personal transporters," Saul Rosser, operations director for the Aquarius Reef Base, told me today.

The crew members also plan to conduct a variety of experiments that play off the fact that the atmospheric pressure inside the Aquarius habitat is equal to the surrounding water pressure at depth — which is about 2.5 times the air pressure at the surface. The experiments will show whether simple tasks such as blowing a bubble or operating a remote-controlled device are tougher at high pressure than they are at normal pressure.

To add a social-media angle, folks who are following the NEEMO mission will be invited to predict the outcome of each experiment. Starting on Thursday, watch for announcements on the following forums: NASA's NEEMO Facebook page and Twitter account, the JSC Education Facebook page and "Teaching From Space" Twitter account, and the European Space Agency's Facebook page and Twitter account. This NASA Web page provides details on how to compete, and what you can win. 

You can also monitor the NEEMO 16 mission via the this Ustream live-video page or this Aquarius webcam page, and watch for updates on Flickr and YouTube. Web-streamed educational activities are planned every day for the next week and beyond, in cooperation with the Challenger Center for Space Science Education. The interactive webcasts will be supplemented by chat capability.

The Aquarius Reef Base is the world's only undersea research station, situated three and a half miles (5.6 kilometers) off Key Largo on a sandy patch of seafloor sitting next to spectacular coral reefs. It's owned by the National Oceanic and Atmospheric Administration and operated by the University of North Carolina at Wilmington. NEEMO ranks among the highlights of Aquarius' research season, but Rosser said there's more to come.

This year marks the 50th anniversary of Aquarius' founding, and to mark the occasion, Rosser and his colleagues are planning an underwater extravaganza next month. He was reluctant to provide the details, but a sneak peek that was posted online says the golden-anniversary mission will be led by two pioneers of marine science, Sylvia Earle and Mark Patterson.

"Stay tuned," Rosser said.

More about NEEMO and Aquarius:

• Astronauts go deep for undersea 'asteroid' trip 
• NASA halts undersea mission due to hurricane
• Aquanauts live in a scientific fishbowl

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

NASA

An artist's conception shows astronauts practicing for asteroid exploration on an underwater rock wall.

A NASA team is going underwater this week in the Florida Keys to lay the groundwork for the space agency's first simulated journey to an asteroid.

Sending astronauts to a near-Earth asteroid ranks as one of the top goals for NASA's retooled vision for space exploration. A year ago, President Barack Obama told NASA to gear up to take on such a mission by the year 2025. Up to that time, NASA had been focusing on a return to the moon — which means that the agency had to retool its mission plans. This week's engineering tests, organized by NASA Extreme Environment Mission Operations, or NEEMO, will help NASA get ready to set off for its new target.

"Even experts don't know what the surface of an asteroid is going to be like," NEEMO project manager Bill Todd said today in a news release. "There may be asteroids that we don't even know about that we'll be visiting. So we're figuring out the best way to do that."

The center of this week's operations is the Aquarius Underwater Laboratory near Key Largo, Fla. "We are now trying to understand the nuts and bolts of what it might take to do a spacewalk on an asteroid or on the moons of Mars," NASA astronaut Mike Gernhardt, a member of the NEEMO team, told me today.

The underwater team isn't working from the Aquarius habitat itself. That part of the simulation will come later. Instead, Gernhardt and his NEEMO teammates are jumping off the deck of a ship, heading down to depths of about 60 feet in the Florida Keys National Marine Sanctuary, and practicing their spacewalking skills on an assortment of boulders and rock walls.

"We've created our own mini-asteroid under the water," Gernhardt said.

The aim is to determine which tools and techniques work best for asteroid exploration. NASA has gotten quite familiar with microgravity operations on the International Space Station, and traveling around the moon or Mars doesn't pose all that much of a challenge, gravity-wise. In a sense, making your way around an asteroid combines the worst of both worlds: Most asteroids are so small, it's virtually like working in zero-G. But unlike the space station, there are no built-in handholds or railings. "We have no control over what this asteroid looks like," Gernhardt said.

NASA

In this illustration, astronauts on a Space Exploration Vehicle nestle up against an asteroid and use jetpacks to move around the surface.

NASA

In this artist's conception, an astronaut uses a network of anchors and tethers to move across an asteroid.

Should astronauts hammer in anchors as they make their way across an asteroid's surface? Should they be anchored to a boom stretching out from their spaceship? Or should they use jetpacks to fly freely just a few inches away from the asteroid? Gernhardt and his colleagues will be trying out all three techniques.

"What we're trying to do is fill in the thousand bits of knowledge to bring this from the artist's concepts to reality," he said.

Here are some of the tools the NEEMO team is testing:

• A 27-foot-long, 300-pound boom that could telescope out from a spaceship (or, for the purposes of the simulation, from a piloted submersible) and lock onto a rocky surface.
• A smaller, 20-pound boom that can be anchored at either end, to be used like a handrail to help get around the surface being explored.
• A dual-thruster backpack that can be used underwater to simulate how a jetpack like NASA's current SAFER system would work in outer space.
• Soil-sampling aids, such as a clamshell grabbag that can scoop up samples, and a large plastic bag that can be stretched over rock outcroppings to keep chipped-off samples from floating away.

"Some of the tools that we developed probably won't work very well at all, but as we work down there we'll probably get ideas for better ways to do things," Gernhardt said.

The knowledge gained during this week's tests will be applied to the planning for a full-up mission simulation in October. That's when NASA's "aquanauts" will take up residence in the Aquarius habitat and practice going out in submersibles to explore underwater asteroids. Mission planners will apply the lessons learned in the Florida Keys in other training environments, including NASA's Neutral Buoyancy Laboratory, Air Bearing Floor and virtual-reality lab as well as the International Space Station.

"It's a bittersweet moment as we wind down the shuttle and the space program as we've known it for the past 30 years," Gernhardt said. But he takes some consolation in the fact that the effort being devoted to NEEMO will pay off on the space station and on other worlds, ranging from near-Earth asteroids to the moon and Mars.

"It's exciting to be working with this great team that we've put together here to develop the tools for future space exploration," Gernhardt said. To keep up with this week's activities, check in with this NEEMO webcast as well as the @NASA_NEEMO Twitter account and the NEEMO Facebook page.

More about asteroids and aquanauts:

• Asteroid goal is riskier than the moon
• Gallery: Seven out-of-this-world destinations
• First step for asteroid mission: Pick the right rock
• Undersea lab serves as inner-space station

Connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. You can also check out "The Case for Pluto," Alan's book about the controversial dwarf planet and the search for new worlds.