Considering how inhospitable Mars is, with no air, -55C (-67 F) temperatures, radiation and all, you might think the quality of sleep on Mars is our last concern. But a new study suggests that a permanent jet lag on Mars might come with some serious health risks, so maybe we should take this more seriously.
The Martian sol, or its solar day, is 24h 39m 35.24409s. That's a tad longer than a day here on Earth which lasts 24h 00m 00.002s. This comes with an inherent mismatch in circadian rhythm -- the internal body clock that regulates wake/rest functions, like hormone production and brain activity.
But is a 40 minute lag too much? If it is, how bad is it? Already, studies show that messing up your internal body clock by working graveyard shifts and flying too often in different time zones can affect health. These include heightened risk of fertility issues and diseases such as diabetes, cancer and cardiovascular disease. One study looked at 3,000 people living in France, about half of whom had experience working shifts. Night shift workers had lower scores on tests of memory, processing speed and overall brain power than regular folks working regular hours. The strongest candidate that would explain the obvious cognitive difference is a disruption in the circadian rhythm. Another study found flight attendants who were chronically jet lagged actually had smaller temporal lobes.
Dr. Andrew Loudon, a biologist at the University of Manchester and colleagues performed the first experiment intended to gauge the effects of having an asynchronous body clock with the planet's rotational motion. They engineered mice that had shorter, 20-hour circadian clocks, and compared them to the control group -- normal mice with 24-hour internal clocks. All the mice were released together in an outdoor pen and studied for 14 months. During this time, the population changed dramatically as the mice bred for several generations. At the end of the experiment, the researchers noted the population was dominated by 24-hour mice. In other words, the 24-hour mice were much fitter to survive, hence reproduce.
"Our study is the first to look at long-term (one-year plus) consequences of abnormal circadian period in an outdoors environment in an animal,” Loudon told The Huffington Post in an email. “People that work on rotational shifts are exposed to abnormal lighting regimes. This is known to be associated with health problems, including increased risk of Type 2 diabetes.”
“A correctly ticking body clock is essential for normal survival in the wild, and this has to be in phase with the rotation speed of the earth."
“Animals with clocks that do not run in synchrony with earth are selected against."
“Thus, the body clock has evolved as an essential survival component for life on earth.”
“The rotation speed of Mars may be within the limits of some people’s internal clock, but people with short running clocks, such as extreme morning types, are likely to face serious intractable long-term problems, and would perhaps be excluded from any plans NASA has to send humans to Mars,“ Loudon said.
The study makes a valid point, but the effects are exaggerated. Deliberately, of course, to spot them, but it doesn't answer what 39minutes of extra jet lag each day might do. Then, mice aren't humans. But we get the idea: add trouble sleeping to the growing list of risks a Martian settler will be exposed to. Though we should remember that we evolved on Earth and hence we have the same circadian rhythm. Would humans change to a sol body clock after a couple of generations? Of course. They'd also adapt to other unique environmental stimuli from Mars. In time, Martians and Earthlings could become so different they might seem alien.
Martian jet lag might not seem like such a big deal, though, when faced with other distractions. The author of The Martian, Andy Weir, shared some in an interview:
"Mars is incredibly quiet because its atmosphere is so thin; also, there’s practically no weather, so there’s no noise to transfer anyway. The inside of a man-made habitat on Mars would have fans to circulate air and run it through scrubbers. It would also have heaters," he said.
"But for the most part, the noisiest thing thing would be the several other astronauts sleeping in close proximity to you," Weird added.
When asked what would he bring to Mars with him to sleep more comfortably, Weir said he bring a "white-noise generator to drown out the sound of your crewmates. The astronauts would probably all have them."
Findings appeared in Proceedings of the National Academy of Sciences.