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Without the sun as a guide, screwing up your inner clock is not hard to do—and it can have drastic consequences. Torturers seeking to “break” their captives often begin by using sensory deprivation to remove all sense of  the passage of time.  As such, astronauts are put on a tight schedule, to keep their circadian rhythm in order. The experimenters described their process in an article published in the Proceedings of the National Academy of Sciences.

Along with time set aside for hygiene  operations, experiments, and personal time, the Mars-500 crew had a mandatory 8.5-hour “sleep time” blocked in to their schedules.  For most of the crew, this worked just fine, and they continued to perform well on the alertness tests they had to occasionally take. But two members had some problems related to their sleep patterns.

As time passed, one of the crew members had fallen out of schedule and began living 25-hour days. While an extra hour may not sound like a big deal, this meant that up to 20% of the time, he was completely out of sync with the rest of the crew—being the one one awake or the only one sleeping. Meanwhile, another member suffered from chronic sleep deprivation. In each case, the group dynamic suffers.

The crew’s activity was using a bracelet with a light sensor and an accelerometer. Data was collected on how active the crew was during wakefulness, rest, and sleep. During the night, they wore caps on their head, an experience that our friend Diego Urbina describes as less than pleasant, and possibly exacerbated the situation. When I asked what parts of the mission were the most difficult, he responded,

Wearing an EEG electrode cap during the night to measure our sleep patterns. A cap that felt like the guy from Hellraiser must have felt, and…didn’t let us sleep.

Also on the subject of sleep quality, Diego also disagrees with some the experiment conclusions regarding his rogue crew members:

I differ with some of the interpretations that were made in the article. For example, a consensus in the crew was that it was easier to sleep there than in real life (with no actual internet or tv). In fact, while there were some funky sleep patterns in one or two people, they were most likely due to the spectrum of the light which was terrible in blue light … and no one was aware of until the end of the mission.

What he’s talking about is the fluorescent lighting inside the module. It was discovered far too late that the lamps were deficient in the 446-477 nm wavelength, which is known to be the most potent for synchronizing sleep/wake patterns. To correct this, and do some science in the process, the ESA sponsored an experiment that involved scheduled exposure to blue light over the course of the day. Their findings will be reported in a separate paper.

In other news, Science Online 2013 is next week!

It is, without a doubt, the place to gather, discuss, and collaborate in all things related to science on the web. I’m doing a workshop on drawing science comics with Katie McKissick of Beatrice the Biologist, as well as co-moderating two discussions. If you’re a fan of the comic and see me down there, do say hello!

Please say hello. It’s so lonely over here.