"That's the first question people ask," said Mike Gernhardt, an astronaut who has flown on four Space Shuttle missions. "How does exploring a lake in a submersible relate to exploring the moon in a rover?"

Gernhardt is one of a half-dozen researchers who trained early this summer to become mini-submarine pilots in preparation for the Pavilion Lake Research Project (PLRP), which took place in July. Pavilion Lake is of interest to scientists because it contains large coral-like structures, known as microbialites, which are believed to have been formed by bacteria.

Researchers have been studying the lake for nearly a decade, and earlier this year, for the first time, they explored it in a pair of one-person submarines known as DeepWorkers.

Gernhardt joined the project because he hoped it would provide insight into the planning process for the next wave of human lunar exploration.

"What we're trying to understand here is this intersection between operational discipline" - following a pre-planned sequence to the letter - "and scientific exploration. There's an optimal balance there and we don't know exactly what that is right now."

Gernhardt leads the NASA group responsible for designing the rovers and spacesuits and for developing the operational procedures that will be used by the explorers who travel to the moon in the next decade.

Although floating underwater in a submarine bears little apparent resemblance to driving around on the dry, dusty, surface of the moon, Gernhardt said there are important similarities that make the Pavilion Lake experience a valuable test bed for future lunar explorers.

For example, both environments are airless, so humans are dependent on their vehicles not only for mobility but for life support as well. But perhaps more importantly, both projects involve exploring terrain that, he said, "human eyes haven't seen" before.

Gernhardt wants to quantify the effectiveness of different approaches to exploration and scientific discovery. He compared the mindset of submarine pilots in the Pavilion Lake work to the activities of astronauts performing a space walk on the Space Shuttle. Astronauts, he said, are given a fixed set of tasks to accomplish, and an explicit set of instructions for achieving their objective; they do not vary from that procedure.

At Pavilion Lake, on the other hand, the goal is more general: to learn as much as possible about the microbialite structures in the lake. Each time the pilots went out in the submarines they had a "flight plan," a specific path to follow, but they also had the option, if they discovered something they wanted to investigate further, to modify the plan and spend more time in one particular location.

"On one of the dives that [PLRP principal investigator] Darlene Lim and I made, we were supposed to go to like ten waypoints and we only went to four. We stayed at the four because there was very interesting stuff" that he and Lim wanted to explore, Gernhardt said. So even though they didn't complete the original flight plan, the dive "actually had a higher scientific return than we had planned. And that's the kind of freedom that I think we need to work toward."

As with Space Shuttle spacewalks, on previous human trips to the moon, astronauts' activities on the surface were conducted strictly by the book and were closely supervised by flight engineers back on Earth. Future plans for human travel to the moon, however, call for setting up semi-permanent lunar bases. Astronauts will spend much longer periods of time on exploratory sorties and Gernhardt thinks they will need more autonomy and decision-making authority.

He believes that rovers and spacesuits should be designed to support this new approach. For example, he has developed a prototype of a small pressurized rover that can accommodate two people comfortably. About the size of a minivan, the rover has cooking, sleeping and lavatory facilities and can travel up to 1000 kilometers on journeys lasting as long as two weeks.

And it has two spacesuits built into its exterior wall. Integration of the spacesuits, Gernhardt hopes, will allow the astronauts to spend most of their time inside, making only short trips out onto the lunar surface to collect samples.

"When you see something that you want to sample, you literally can open the door to the back of the spacesuit, step in the suit and close the door. Our goal is that ten minutes later you'd be boots-on-the-surface and picking up rocks," he said. "They'll drive along, see something, pop into the suits, work for a couple hours, pop back in, and have lunch."

His experience piloting a sub at Pavilion Lake helped convince Gernhardt of the value of this approach. The submarines, he said, were great for getting around and doing large-scale surveys, but they proved a bit clumsy when it came time to collect samples. He described one attempt to use the sub's robotic arm to pick up a beer bottle "that had microbialites growing on it. But it took me probably ten minutes to get the beer bottle. And I knocked a lot of microbialites off in the process. I'd much rather have jumped in a suit, gone out there, picked up the beer bottle," and returned to the sub, he said.

Gernhardt and his PLRP colleagues are hopeful that in future field work they'll get a chance to do just that.

Nuytco, the Canadian company that built the DeepWorker subs, is working on a pressurized underwater diving suit that, used in combination with small submarines for traversing long distances, will enable divers to collect samples by hand from the deepest parts of the lake without having to resort to dangerous decompression diving.

In the mean time, Gernhardt is preparing for an extensive field test this fall that will compare the effectiveness of the small-pressurized-rover-with-integrated-spacesuits design to other rover and spacesuit designs.

Different operational approaches, involving differing degrees of autonomy, will also be tried out. Such direct comparisons, Gernhardt hopes, will help NASA decide which technologies, and which approaches to exploration, yield the greatest scientific results.

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