Lack of gravity can lead to social, emotional impairment for astronauts

PHILADELPHIA — A trip to Mars could take a toll on astronauts’ minds, as living in zero gravity causes them to think other crew members look angry, new research suggests. Weightlessness leaves them more likely to interpret facial expressions as angry rather than happy or neutral. The phenomenon could endanger missions to the Red Planet, warn scientists.

“Astronauts on long space missions, very much like our research participants, will spend extended durations in microgravity, confined to a small space with few other astronauts,” says study lead author Professor Mathias Basner, a psychiatrist at the University of Pennsylvania, in a statement. “NASA’s current plans for a return mission to Mars lasts approximately 1,000 days (two years and nine months).”

This is more than twice the current record of 438 continuous days in space held by Russian cosmonaut Valery Polyakov.

Zero gravity / Mars study
Test participants experiencing artificial weightlessness on a centrifuge.

“The astronauts’ ability to correctly ‘read’ each other’s emotional expressions will be of paramount importance for effective teamwork and mission success,” says Prof Basner. “Our findings suggest their ability to do this may be impaired over time.”

How gravity impacts astronauts’ health

Humans have evolved to exist within Earth’s gravity (1 gravity), not in the weightlessness of space (0 g) or the microgravity of Mars (0.3 g). The fluid shifts are also linked with space motion sickness, headaches, nausea, and blurred vision.

In space, there is no gravity to pull blood into the lower part of the body. Instead, it goes upwards. This has been dubbed “puffy head bird legs syndrome,” due to bodily fluids shifting towards the head, causing round, puffy faces, bulging neck vessels, and thin legs.

Astronauts feel dizzy and sometimes even faint when they return to Earth. Previous studies have shown it leads to structural changes in the brain, although little is known about how this translates to behavior.

For the new study, sixteen volunteers spent 60 consecutive days in the bed-rest position with their heads tilted at a slight six-degree angle to mimic microgravity. Another eight not exposed to the strict regime acted as a control group.

“Participants regularly completed ten cognitive tests relevant to spaceflight specifically designed for astronauts such as spatial orientation, memory, risk-taking, and emotion recognition. The main goal was to find out whether artificial gravity for 30 minutes each day — either continuously or in six five-minute bouts — could prevent the negative consequences caused by decreased mobility and headward movement of body fluids that are inherent to microgravity experienced in spaceflight,” explains Prof Basner.

Zero gravity / Mars study
Head-down bed rest at a slight six-degree angle is the standard way of simulating the effects of microgravity on Earth.

“A modest but statistically significant slowing across a range of cognitive domains was found during head-down bed rest. These changes were observed early and did not further worsen or improve with increasing time — except for emotion recognition performance,” he adds. “With increasing time, participants required longer to decide which facial emotion was expressed. They were also more likely to select categories with negative over neutral or positive attractiveness.”

Safe mission to Mars

The study also found that impaired cognitive performance could not be improved by short periods of artificial gravity. Artificial gravity counter-measures consisted of spinning the participants on a centrifuge. Positioned like an arm on a clock with their head in the middle, they were spun around at the speed of one revolution every two seconds.

“There are two ways to produce gravity in spaceflight: rotate the whole spacecraft/station, which is expensive, or just rotate the astronaut. The centrifuge could be self-powered — doubling up as an opportunity for exercise,” says study co-author Dr. Alexander Stahn, also from the University of Pennsylvania. “Unfortunately, we found the artificial gravity countermeasures in our study did not have the desired benefits. We are currently performing additional analyses using functional brain imaging to identify the neural basis of the effects observed in the present study.” In the future, the team plans to test longer-duration artificial gravity countermeasures and to vary the degree of social isolation.

Zero gravity / Mars study
Long-exposure photo of the centrifuge used to simulate microgravity in the research subjects.

“In conclusion, 60 days of head-down bed rest were associated with moderate cognitive slowing and changes in emotion recognition performance. These effects were not mitigated by either continuous or intermittent exposure to artificial gravity for 30 minutes daily,” notes Prof. Basner. “We cannot say whether the effects observed on the emotion recognition test were induced by simulated microgravity or by the confinement and isolation inherent to the study, with separate bedrooms and sporadic contact to the study team. Future studies will need to disentangle these effects.”

NASA hopes to send humans to Mars by 2035. A typical trip takes seven months. Astronauts will be expected to stay more than a year before coming back, living in microgravity for nearly three years.

This experiment is published in Frontiers in Physiology.

SWNS writer Mark Waghorn contributed to this report.

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