Space travel may extend the range of our restless species, but ironically, to get even as far as our neighboring planet Mars, astronauts would have to endure months of extreme confinement, deprived of the freedom to roam or escape from each other.

Scientists know being cooped up inside this way could be stressful, perhaps fatally so. To learn how humans will deal the necessary confinement and isolation of a Mars mission, six volunteers spent 17 months sitting in a mock spacecraft the size of two connected Winnebagos. There was even a fake Mars landing lasting about 30 days, though the craft, located near Moscow, never left the ground.  

While the all male crew were in there, psychiatry professors from Penn were monitoring their every move, studying the effects of the mission on the men’s moods, feelings, and ability to perform. 

On Monday the researchers announced the results of their observations, including a surprising range of reactions among the volunteers. Some got out of sync or had trouble sleeping and lost focus, while others actually got sharper during the mission.

“We were getting more excited as time went by and we knew we were seeing something surprising,” said Penn psychiatry professor David Dinges, chief of the division of Sleep and Chronobiology.  He is co-author of the first scientific paper on the volunteers, which was published this week in the Proceedings of the National Academy of Sciences.  

He said he was surprised to learn that all the crew members unconsciously stopped moving as much, and most slept more – a state Dinges calls hypokinesis. “Even when awake and active they were moving less and when they were asleep they were also moving less,” he said. Their activity diminished gradually over the first six months of the mission.

The project, officially called Mars 500, was “launched” by the European Space Agency and a Russian group called the Institute for Medical and Biological Problems. The six volunteers came from Russia, France, Italy and China and had medical, engineering or military backgrounds similar to those of astronauts. They went into the craft in June 2010 and emerged in November of 2011.

Dinges believes that psychological problems could be as important as the bone loss, radiation and other physical hazards that would face a real Mars-bound crew, with a flight time of at least six months each way. It’s been documented that astronauts aboard Skylab, Mir, and the International Space Station have suffered various problems from quarrels to loneliness to chronic sleeplessness. In addition to the confinement and isolation, long-duration astronauts are deprived of sunlight and the day-night cycle that helps us and many other living things regulate sleep, eating and other behavior.

This week’s scientific results come from the second try for this experiment. A previous run with a mixed sex crew was abandoned after 240 days. While the details were not widely publicized, the London Guardian reported that the trouble started when the crew members were allowed to have some vodka as a holiday treat on New Year’s Eve. Two male Russian crew members reportedly got into “A bloody fistfight” and one of the men then “dragged the female crew member away from the cameras and tried to force his tongue down her throat.” 

This is not a scenario you’d want to see 30 million miles away from home. This time the experimenters decided on a single-sex crew and, just to be safe, no booze was allowed. 

While they were inside, the volunteers wore wristbands with monitors that recorded how much and how vigorously they moved and how soundly they slept. The volunteers did a daily laptop-based task called a psychomotor vigilance test, which required them to hit a key when they saw something flash on the screen. When people are sleep deprived, they tend to react more slowly or jump the gun, reacting when there’s no signal.

Webcams also recorded their facial expressions, and special software flagged when they appeared exhausted, angry or depressed. To avoid interfering with the experiment, the researchers read the data from thumbnail-sized data cards that went out with the garbage.

The measured decrease in activity could cause a problem on a real mission, where astronauts need to exercise to keep from losing their muscles and bones, said Penn psychiatrist Mathias Basner, who collaborated with Dinges on the project.

Basner, who is also an expert on sleep and circadian rhythms, said he was surprised at the individual differences they observed. One crew member began waking an sleeping in cycles of 25 hours, which put him out of sync with the rest of the volunteers.

Another man had insomnia, and ended up sleeping less as time went on. His performance on the psychomotor vigilance test showed increasing errors. “It was one of the most important findings that there was such differential vulnerability to the isolation and confinement,” Basner said.

Several of the subjects did extremely well, actually improving their vigilance and reaction times, which  Basner attributes to their getting better sleep. “After the first three or four weeks they all of a sudden had time to satisfy their individual sleep needs,” he said. These men may have been deprived of sleep during their normal lives. “Sleep is regarded as a weakness by many people,” he said.

He and Dinges both see sleep as important for consolidating memory, synthesizing hormones and resetting the brain. From their perspective, the expression should be, if you don’t snooze, you lose.

Astronauts have already flown for long periods - the record holder is cosmonaut Valery V. Polyakov at 438 days. But because they are relatively close to Earth, they get to see a change or two of companions over the course of their missions.

Dinges said the type of sustained group confinement observed in this experiment is unique – the closest thing to it might be the great polar expeditions of the early 20th century. When trying to navigate over the North Pole, for example, the crew of explore Fredtjof Nansen lived in an ice-locked ship for three years, though there were able to leave the ship and walk around.

Upon interviewing the crew members, Dinges learned that they had no sense they were moving less. When he asked why they often went off to sit in certain rooms, however, they reported that they needed some privacy, not just from each other but from the scientists and members of mission control who were constantly watching and monitoring.  “That might have been a contributor to their decreased activity.”

Dinges said he and Basner are publishing a second paper later this year that will focus more on the effects of the mission on mood and emotions. He thinks the experiment will give them a wealth of information that could be used to design a space environment to promotes effective sleep, thinking and behavior. It might also change who space agencies perceive as having the right stuff.