NEW YORK - A manned mission to Mars could be put at risk by astronauts too tired to perform duties by the time they arrive on the planet, a study suggests.
In a 17-month simulation of a mission to Mars, 4 of 6 astronauts became increasingly sedentary and experienced problems in performance associated with sleep deprivation, according to research released Monday in the journal Proceedings of the National Academy of Sciences. The problems occurred early in the mission, scientists said.
Locked in a spaceship-like habitat in Moscow for 17 months to resemble a trip to and from the Red Planet, plus 3 days for a the visit, the would-be astronauts performed experiments and simulated emergency activities. The most sleep-deprived of the six crew members was responsible for about 80 percent of errors on assigned tasks, suggesting maintaining natural sleep cycles is crucial for the success of interplanetary missions.
"We're not saying this isn't feasible, but we've identified these areas where we may have to do something," Mathias Basner, a study author and an assistant professor of sleep and chronobiology in psychiatry at the University of Pennsylvania in Philadelphia, said in a telephone interview.
The scientists monitored the participants' sleep during the 520-day simulation of a Mars mission using a wrist device. Additionally, they tested the crews' behavioral alertness. The simulation was conducted by the Russian Academy of Sciences' Institute for Biomedical Problems and the Russian Space Agency. The European Space Agency cooperated.
The would-be astronauts were locked in a container in Moscow on July 3, 2010, and emerged on Nov. 4, 2011. The six men participated in more than 90 experiments and scenarios including emergencies and 20-minute communication delays to their mission command. The time accounted for the 250-day trip to Mars, 30 days on the planet, and 240 days back.
Of the six crew members, only two didn't experience some kind of sleep trouble. One crew member developed mild depression toward the end of the mission, despite having been screened before the simulation began.
"There were two crew members who did outstanding and adapted perfectly, and we would feel good about sending those to Mars," Basner said. "The other four had major problems in the domains we were looking into."
He suggested lights that better simulate sunlight as received on earth might be helpful. The monotony of the environment may also be responsible for some of the mood and sleep disruptions, Basner said.
Many of the health issues developed early and persisted throughout the mission, Basner said. That means that if scientists want to test potential remedies for the sleep disruptions, the simulations don't have to be as long.
"Probably we don't need a 17-month mission to see them, just 2 to 3 months, which gives us more opportunities to do more of these studies," he said.
The research was supported by the National Aeronautics and Space Administration, the National Space Biomedical Institute and others.