Psychological and behavioral changes during confinement in a 520-day simulated interplanetary mission to mars

Abstract

Behavioral health risks are among the most serious and difficult to mitigate risks of confinement in space craft during long-duration space exploration missions. We report on behavioral and psychological reactions of a multinational crew of 6 healthy males confined in a 550 m(3) chamber for 520 days during the first Earth-based, high-fidelity simulated mission to Mars. Rest-activity of crewmembers was objectively measured throughout the mission with wrist-worn actigraphs. Once weekly throughout the mission crewmembers completed the Beck Depression Inventory-II (BDI-II), Profile of Moods State short form (POMS), conflict questionnaire, the Psychomotor Vigilance Test (PVT-B), and series of visual analogue scales on stress and fatigue. We observed substantial inter-individual differences in the behavioral responses of crewmembers to the prolonged mission confinement and isolation. The crewmember with the highest average POMS total mood disturbance score throughout the mission also reported symptoms of depression in 93% of mission weeks, which reached mild-to-moderate levels in >10% of mission weeks. Conflicts with mission control were reported five times more often than conflicts among crewmembers. Two crewmembers who had the highest ratings of stress and physical exhaustion accounted for 85% of the perceived conflicts. One of them developed a persistent sleep onset insomnia with ratings of poor sleep quality, which resulted in chronic partial sleep deprivation, elevated ratings of daytime tiredness, and frequent deficits in behavioral alertness. Sleep-wake timing was altered in two other crewmembers, beginning in the first few months of the mission and persisting throughout. Two crewmembers showed neither behavioral disturbances nor reports of psychological distress during the 17-month period of mission confinement. These results highlight the importance of identifying behavioral, psychological, and biological markers of characteristics that predispose prospective crewmembers to both effective and ineffective behavioral reactions during the confinement of prolonged spaceflight, to inform crew selection, training, and individualized countermeasures.

Conflict of interest statement

Competing Interests: Jeffrey P. Sutton and Mathias Basner are PLOS ONE editorial board members. Daniel Mollicone is CEO of Pulsar Informatics Inc. and Igor Savelev was employed by Wyle at the time the authors performed the study. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials.

Figures

Figure 1. Cumulative self report scores show differential reactions to confinement.

Cumulative scores are plotted for each crewmember (identified by lower case letters a–f) relative to time in mission for the 8 self-report measures that showed significant differences between crewmembers (see Table 2). Beck-Depression Inventory-II and Profile of Mood States Short Form (POMS) scores were not transformed to a range from 0 to 100 for this figure.

Figure 2. Perceived conflicts throughout the simulated Mars mission.

The number of conflicts with mission control (left panel) and other crewmembers (middle panel) were counted for 30-day periods relative to a 30-day period surrounding the landing on Mars between mission days 244 and 273. One conflict was counted if the crewmember recorded either a current conflict and/or a conflict in the past seven days. Conflicts (reported once weekly) with mission control peaked during the Mars landing period, were lower in the second half compared to the first half of the mission (dashed lines represent averages over pre- and post-landing periods), and were reported more often than conflicts among crewmembers. The right panel shows the cumulative number of weeks with conflicts relative to time in mission by crewmember. The majority of conflicts were reported by crewmembers e and f.

Figure 3. Crew interactions were facilitated by a core group.

During de-briefs, each crewmember was asked to report the two crewmembers interacted with most frequently during the mission. Arrows pointing to a crewmember indicate the number of times he was mentioned by others; those pointing away designate with whom he indicated he most often interacted. Circle size indicates the frequency with which a crewmember was identified as interacted with most frequently.