There is nothing like a regular sleep schedule to keep you healthy, especially on a long voyage to Mars.

On June 3, 2010, a six-man team of international volunteers was sealed into a 550-cubic-meter spacecraft-like compartment at a Russian Academy of Sciences facility to simulate a 520-day round-trip mission to the Red Planet. During the project, sponsored in part by the European Space Agency, the 'crew' conducted experiments and scenarios to collect psychological and medical data on the effect of long-term deep-space flight.

Researchers from the University of Pennsylvania and Baylor College of Medicine analyzed the data in a study published in the journal Proceedings of the National Academy of Sciences. They found that the crew became more sedentary as the months passed, and most of them also experienced a decrease in the quality of their sleep and alertness.

Co-lead author Mathias Basner says that demonstrates the need to ensure that Earth's natural circadian rhythm is artificially simulated in future spacecraft and planetary habitats, so crew members can maintain a normal and healthy sleep-wake cycle.

The findings are also applicable here on Earth, where many people in industrialized countries have sedentary lifestyles, as well as disrupted sleep patterns because of work and school schedules. Co-lead author David Dinges notes “the human body's need for sleep is as essential as our need for food and water.”