Interplanetary Jet Lag: How NASA Rover Staff Adjust to Martian Time

By Veronique Greenwood | October 1, 2012 3:03 pm

spacing is important
On the left, shifting hormone levels over time. On the right, work (gray) and sleep (black) hours of NASA staff on Martian time gradually cycle around the clock.

Mars has an ever-so-slightly longer day than we do: 24 hours and 39 minutes, to be exact. To control solar-powered rovers like Phoenix and Curiosity, NASA teams must shift their sleeping cycles to match, and it’s a lot harder than it sounds: that fraction of an hour extra means that their sleep schedules creep every day, so while 1 pm might be the middle of the night one week, say, it will have become breakfast time by the next. Staying on Mars time is so grueling that staff for the Sojourner rover in 1997 bailed on the schedule a third of the way through the mission.

But there may be ways of making the shift more graceful. In a recently published study following personnel of the Phoenix rover mission in 2008, a team of researchers provided training sessions to facilitate the switch to Mars time, including tips on when to drink coffee and when to nap, and then explored whether exposure to blue light, which works on photosensitive cells in the eye involved in circadian management, resulted in better adjustment.

Sixteen subjects turned on a blue light at their desks at the beginning of each work “day” and provided a log of their activities and fatigue level and frequent samples of urine to the researchers, who used the levels of a hormone in the urine to evaluate whether the subjects were fitting themselves biologically to Martian time.

When the hormone levels were plotted, the researchers found that they supported the idea that the subjects were adapting to the longer day. Plotting the data under the assumption of a 24-hour day resulted in a garbled picture with no pattern visible; trying a slightly longer day revealed the characteristic rise and fall of the hormone levels that scientists have come to expect.

Was this because of the blue light, though, or was it the result of the basic sleep training? Several subjects who didn’t use the blue lights managed to make the switch to Mars time all the same, and the team suggests that there were enough factors beyond their control—for instance, subjects’ exposure to the sun outside of work—to muddy the data in regards to the blue light. They point out, though, that previous studies have shown that sleep scheduling without light manipulation won’t shift people to Martian time. They hope that in future studies, they’ll be able to go farther—replacing all the bulbs in the office, for instance, with blue ones.

CATEGORIZED UNDER: Health & Medicine, Space, Top Posts
  • bystander

    What does distance from the Sun have to do with the length of the day? I thought it was dependent on rotational speed of the planet.

  • Erin

    Tried to look at the study, but PubMed says it was published today and is under embargo until April 2013 :( This is entirely contrary to my understanding of how embargoes work.

    Until I can actually read the damn thing, though…

    The graph concerns me. It’s important in circadian studies to establish a subject’s circadian period and phase angle before the experiment begins. If any such data has been gathered, it isn’t displayed here.

  • http://www.universetoday.com Fraser Cain

    Hi Veronique, I’m sure you’re going to get a bunch of these, so get that edit in quick. The increased orbital distance of Mars has nothing to do with its length of day. It’s just coincidence that it’s close to 24 hours.

    • Veronique Greenwood

      Ye gods, how embarrassing! Thanks for the swift catch, all, and apologies for the mistake.

  • Tony

    @bysteander: Because Mars is further away from the sun, it takes longer for the planet to revolve around the sun so a year on Mars is longer than a year on Earth. (Insert next logical step here). And that’s why the length of a day on Mars is related to its distance from the sun. QED.

    I’d love to hear an explanation if it’s true that distance from the sun affects the length of a day, but as far as I can figure out the author has just confused revolutions and rotations.

  • Steven M

    Same as bystander: Mars’ distance from the sun has nothing to do with its period of rotation or the length of its day. Jupiter’s day is only 9.8 hours long and it is much farther away (and larger) than Mars.

  • Gib

    Well, the orbit of the planet around the sun is responsible for exactly 1 day per year. (It makes the difference between a solar day and a sidereal day).

    The rest of the days are due to the rotation of the planet, so I’d say the author stuffed up.

    Now, it may be that when the planets were being formed, that planets closer to the sun got more rotational momentum than those further out, resulting in longer days for Mars, but I don’t think that’s what the author meant….

  • Chris

    Curiosity is not solar powered, it is nuclear powered. But it can only work during the day since it needs to see where it is going! Also to communicate with the rover we need to be able to see it, which is during the Martian day.

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