Learning to live on a Mars day: Fatigue countermeasures during the Phoenix Mars Lander mission

Laura K. Barger, Jason P. Sullivan, Andrea S. Vincent, Edna R. Fiedler, Laurence M. McKenna, Erin E. Flynn-Evans, Kirby Gilliland, Walter E. Sipes, Peter H. Smith, George C. Brainard, Steven W. Lockley

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


Study Objectives: To interact with the robotic Phoenix Mars Lander (PML) spacecraft, mission personnel were required to work on a Mars day (24.65 h) for 78 days. This alien schedule presents a challenge to Earth-bound circadian physiology and a potential risk to workplace performance and safety. We evaluated the acceptability, feasibility, and effectiveness of a fatigue management program to facilitate synchronization with the Mars day and alleviate circadian misalignment, sleep loss, and fatigue. Design: Operational field study. Setting: PML Science Operations Center. Participants: Scientific and technical personnel supporting PML mission. Interventions: Sleep and fatigue education was offered to all support personnel. A subset (n = 19) were offered a short-wavelength (blue) light panel to aid alertness and mitigate/reduce circadian desynchrony. They were assessed using a daily sleep/work diary, continuous wrist actigraphy, and regular performance tests. Subjects also completed 48-h urine collections biweekly for assessment of the circadian 6-sulphatoxymelatonin rhythm. Measurements and Results: Most participants (87%) exhibited a circadian period consistent with adaptation to a Mars day. When synchronized, main sleep duration was 5.98 ± 0.94 h, but fell to 4.91 ± 1.22 h when misaligned (P < 0.001). Self-reported levels of fatigue and sleepiness also significantly increased when work was scheduled at an inappropriate circadian phase (P < 0.001). Prolonged wakefulness (≥ 21 h) was associated with a decline in performance and alertness (P < 0.03 and P < 0.0001, respectively). Conclusions: The ability of the participants to adapt successfully to the Mars day suggests that future missions should utilize a similar circadian rhythm and fatigue management program to reduce the risk of sleepiness-related errors that jeopardize personnel safety and health during critical missions.

Original languageEnglish (US)
Pages (from-to)1423-1435
Number of pages13
Issue number10
StatePublished - Oct 1 2012


  • Circadian
  • Light
  • Performance
  • Shift work
  • Sleep

ASJC Scopus subject areas

  • Clinical Neurology
  • Physiology (medical)


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