Spaceflight sleep research reveals how disrupted light cues and schedules harm astronaut alertness

By the Everything Space news desk · 02 Oct 2026 · written from the sources below

Image: Phys.org

Studies from Artemis II and Mars simulations show how missing day-night cues can chip away at astronauts' sleep and performance, raising safety concerns for future missions.

Astronauts in orbit face a body clock problem unlike anything on Earth: with a spacecraft circling the planet roughly every 90 minutes, crews see about 16 sunrises and sunsets a day, far too many to treat each as a bedtime cue. Mission planners instead have to manufacture artificial schedules for sleep, meals, exercise and work, since the usual solar signals that anchor a person's internal clock simply are not available in the same way.

Sleep researchers describe two separate systems that normally work together: a circadian clock that tells the brain when it expects to be asleep or awake, and a buildup of sleep pressure that increases the longer someone stays awake. Spaceflight can pull these apart, leaving astronauts physically exhausted but biologically primed for daytime, or vice versa. Despite typically being given roughly eight and a half hours of opportunity to sleep each day, astronauts have often only managed around six to six and a half hours, and research on the International Space Station has tied that level of sleep restriction to measurable declines in vigilant attention, a concern in an environment where missed signals carry real risk.

During NASA's Artemis II lunar flyby mission, astronauts wore movement and sleep monitors as part of a broader study tracking how rest and activity shifted across training, the flight itself and recovery afterward, alongside measures of cognition and team performance. Separately, NASA has tested whether pink noise played through a headband during daytime sleep periods could improve alertness after waking; an early study of a small group of adults found no measurable difference in grogginess or attention in the first 40 minutes after waking compared with a control condition.

Lighting aboard spacecraft is also managed deliberately, with blue-enriched light used to support alertness and circadian alignment during waking hours and dimmer, blue-depleted light meant to ease the transition to sleep. But recent testing found that lighting optimized to boost melatonin before sleep also impaired astronauts' ability to distinguish colors, creating a tension between lighting that helps the body clock and lighting needed to read color-coded equipment or warnings. Caffeine, meanwhile, can boost short-term alertness but also disrupts subsequent sleep, trading one problem for another.

Looking beyond Earth's 24-hour cycle raises a further challenge: a Martian day runs about 24 hours and 40 minutes, a small but persistent mismatch that forces continual adjustment of the body clock. A current yearlong Mars simulation based at Johnson Space Center recently shifted its four-person crew from an Earth schedule onto this longer Martian day, a shift that will continue until the simulation concludes, offering a preview of the unusual form of jet lag that future Mars explorers may have to manage.

Written in Everything Space’s own words by our news-desk model from the sources above, and checked against them in code: every number in this report appears in its sources, and no sentence is copied from them.