Mars missions leader has found the secret of the 25-hour day

Cornell astronomers James Bell, left, and Steven Squyres plan to live on Mars time while at the Jet Propulsion Laboratory in Pasadena, Calif., for the duration of the Mars rover mission. The two members of the rover team pose in front an image of the rover, Nov. 14. Nicola Kountoupes/University Photography

By Kate Becker

Steven Squyres, the principal investigator for the science instruments aboard the Spirit and Opportunity Mars rovers, juggles his commitments to the four space missions he is actively involved in, as well as to his teaching and advising duties, with an energetic ease that makes some wonder if he has found the secret to a 25-hour day.

Well yes, actually, he has.

Not 25 hours, to be exact, but 24 hours, 39 minutes and 35 seconds, the length of one Martian day, or "sol."

As the rovers' landing dates draw closer (read related story), Squyres is preparing to live on Mars time for the duration of the mission, expected to be about four months. Spirit is scheduled to touch down in the red planet's Gusev Crater on Jan. 3; its twin, Opportunity, will land at Meridiani Planum on Jan. 25.

"Our vehicles are tied to the Martian day/night cycle," said Squyres, professor of astronomy at Cornell. "They rely on a vision system to avoid obstacles," and being solar powered they must operate during daylight and "sleep" at night.

Because the rovers' daily communications windows also are tied to this cycle, Squyres, along with almost 100 other scientists and engineers, must lengthen his days to stay in sync.

Squyres admits that the longer days, at first, seem attractive -- "you get to sleep in 39 minutes later every day" -- but points out that there is "very little hard data on the physiological impact of extended Mars-time living."

The fundamental problem, said Squyres, is that the human cycle is adjusted to a 24-hour cycle.

The entire rover team will work from the headquarters of the mission manager, the Jet Propulsion Laboratory in Pasadena, Calif. They already have rented apartments in a quiet neighborhood equipped with light-tight blackout shades, and many team members will wear specially made Mars watches that record an additional 39 minutes, 35 seconds every day. But when rover team members step outside, they will be bombarded with external stimuli running on the 24-hour clock to which their bodies are accustomed.

"We decided we needed to get some serious advice in this area," said Squyres. When, jet-lagged and exhausted, he ran into Cornell sleep researcher James Maas at the Pittsburgh airport in 2000, both realized that a collaboration would be a boon for data-hungry sleep researchers and for the rover team.

"While we were doing our own experiments, there was the opportunity for us to be the subject of someone else's experiment," said Squyres."

Consequently about 40 members of the rover team will be the subjects of the sleep study led by Harvard professor Charles Czeisler. Small wristwatch-like accelerometers will keep a record of the scientists' motion through the days and nights of the Mars mission. From the accelerometer readings, Czeisler's team will deduce when the scientists were awake and when they were asleep.

Workshops with sleep experts from Harvard, Brown, Stanford and the NASA Ames research center also have helped shape the Mars team's strategies.

"The key is not to overschedule people," said Squyres. Scientists will stick to a six-sol workweek, working four sols and taking a two-sol weekend.

But engineers on the team with permanent homes in Pasadena will get a longer, three-sol weekend. The engineers "have groceries to buy, lawns to mow, PTA meetings to go to," and must contend with more signals from the 24-hour world than the visiting scientists, said Squyres.

Squyres is most worried, though, about the "wicked case of Martian jet lag" he will get when Opportunity lands on Jan. 25. The rover's landing site is almost 180 degrees away from Spirit's, meaning that when Squyres leaves the Spirit team to join the Opportunity group, he will be about 12 hours off schedule. It is the Martian equivalent of a trip from Ithaca to Australia -- without the benefit of a daylong plane ride during which to adjust.

There is one vestige of Earth time Squyres won't be able to escape, though: the press conference. So if, come January, Squyres looks a bit bleary-eyed in front of the cameras, remember that it might just be 2:30 a.m. back in Gusev Crater.